$SBSI
SOUTHSIDE BANCSHARES INC Stock $sbsi

$sbsi Overview Financials Valuation SEC Filings Company Website

2018 Q4 Form 10-K Financial Statement

#000070543220000022 Filed on February 28, 2020

Income Statement

Concept	2018 Q4	2018 Q3	2018 Q2
Revenue	$58.02M	$57.15M	$56.80M
YoY Change	15.8%	22.98%	23.45%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$3.400M	$3.500M	$3.500M
YoY Change	17.24%	40.0%	45.83%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense	$15.61M	$14.74M	$13.69M
YoY Change	32.33%	28.05%	29.3%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$19.90M	$22.50M	$23.56M
YoY Change	22.84%	22.25%	32.12%
Income Tax	$2.521M	$2.192M	$3.360M
% Of Pretax Income	12.67%	9.74%	14.26%
Net Earnings	$17.38M	$20.30M	$20.20M
YoY Change	68.24%	39.91%	39.51%
Net Earnings / Revenue	29.96%	35.52%	35.57%
Basic Earnings Per Share	$0.50	$0.58	$0.58
Diluted Earnings Per Share	$0.50	$0.58	$0.57
COMMON SHARES
Basic Shares Outstanding	35.16M shares	35.11M shares	35.06M shares
Diluted Shares Outstanding		35.29M shares	35.23M shares

Balance Sheet

Concept	2018 Q4	2018 Q3	2018 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$120.7M	$174.1M	$232.1M
Short-Term Investments
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets
YoY Change
LONG-TERM ASSETS
Property, Plant & Equipment	$136.0M	$133.9M	$132.6M
YoY Change	1.74%	25.06%	25.15%
Goodwill	$201.1M	$201.1M	$201.2M
YoY Change	-0.06%	119.75%	119.89%
Intangibles	$17.78M	$19.01M	$20.29M
YoY Change	-22.68%	462.56%	438.55%
Long-Term Investments	$12.10M
YoY Change
Other Assets	$9.800M	$16.40M	$15.40M
YoY Change	-19.67%	-24.77%	-31.25%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$6.123B	$6.105B	$6.250B
YoY Change	-5.76%	11.32%	12.04%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt	$36.80M	$9.000M	$8.300M
YoY Change	287.37%	-99.1%	-99.19%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$36.80M	$9.000M	$8.300M
YoY Change	287.37%	-1.1%	-1.19%
LONG-TERM LIABILITIES
Long-Term Debt	$158.7M	$158.6M	$158.6M
YoY Change	0.13%	0.13%	0.13%
Other Long-Term Liabilities	$52.60M	$70.50M	$46.30M
YoY Change	21.76%	30.31%	-25.8%
Total Long-Term Liabilities	$211.3M	$229.1M	$204.9M
YoY Change	4.76%	7.81%	-7.2%
TOTAL LIABILITIES
Total Short-Term Liabilities	$36.80M	$9.000M	$8.300M
Total Long-Term Liabilities	$211.3M	$229.1M	$204.9M
Total Liabilities	$5.392B	$5.353B	$5.498B
YoY Change	-6.12%	8.61%	9.28%
SHAREHOLDERS EQUITY
Retained Earnings	$64.80M	$58.58M	$48.84M
YoY Change	97.25%	128.13%	151.66%
Common Stock	$809.8M	$808.9M	$806.8M
YoY Change	0.63%	33.95%	34.02%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$93.06M	$45.97M	$46.55M
YoY Change	97.55%	-2.8%	-2.68%
Treasury Stock Shares	4.120M shares	2.673M shares	2.739M shares
Shareholders Equity	$731.3M	$752.5M	$751.8M
YoY Change
Total Liabilities & Shareholders Equity	$6.123B	$6.105B	$6.250B
YoY Change	-5.76%	11.32%	12.04%

Cashflow Statement

Concept	2018 Q4	2018 Q3	2018 Q2
OPERATING ACTIVITIES
Net Income	$17.38M	$20.30M	$20.20M
YoY Change	68.24%	39.91%	39.51%
Depreciation, Depletion And Amortization	$3.400M	$3.500M	$3.500M
YoY Change	17.24%	40.0%	45.83%
Cash From Operating Activities	$19.30M	$32.60M	$28.80M
YoY Change	34.97%	13.59%	80.0%
INVESTING ACTIVITIES
Capital Expenditures	-$4.500M	-$3.700M	-$3.200M
YoY Change	80.0%	15.63%	23.08%
Acquisitions
YoY Change
Other Investing Activities	-$61.90M	$101.6M	$81.90M
YoY Change	-173.78%	318.11%	36.5%
Cash From Investing Activities	-$66.40M	$97.80M	$78.90M
YoY Change	-181.67%	361.32%	37.7%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-6.300M	-188.4M	-138.4M
YoY Change	-92.27%	86.35%	63.79%
NET CHANGE
Cash From Operating Activities	19.30M	32.60M	28.80M
Cash From Investing Activities	-66.40M	97.80M	78.90M
Cash From Financing Activities	-6.300M	-188.4M	-138.4M
Net Change In Cash	-53.40M	-58.00M	-30.70M
YoY Change	-478.72%	13.28%	174.11%
FREE CASH FLOW
Cash From Operating Activities	$19.30M	$32.60M	$28.80M
Capital Expenditures	-$4.500M	-$3.700M	-$3.200M
Free Cash Flow	$23.80M	$36.30M	$32.00M
YoY Change	41.67%	13.79%	72.04%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
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CY2019	dei	Amendment Flag AmendmentFlag	false
CY2019	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2019	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2019	dei	Entity Central Index Key EntityCentralIndexKey	0000705432
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CY2018Q4	sbsi	Loans And Leases Receivable Related Parties As Percent Of Shareholders Equity LoansAndLeasesReceivableRelatedPartiesAsPercentOfShareholdersEquity	0.006	Rate
CY2017Q4	sbsi	Loans Receivable Modifications Commitmentto Lend LoansReceivableModificationsCommitmenttoLend	0	USD
CY2018Q4	sbsi	Loans Receivable Modifications Commitmentto Lend LoansReceivableModificationsCommitmenttoLend	0	USD
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CY2018	sbsi	Securities Transferred From Available For Sale To Held To Maturity SecuritiesTransferredFromAvailableForSaleToHeldToMaturity	0	USD
CY2017	sbsi	Stock Dividends Percentage Of Common Stock StockDividendsPercentageOfCommonStock	0.025	Rate
CY2019	sbsi	Supplemental Unemployment Benefits Disability Related Benefits Maximum Benefit Provided As Ratio Of Final Salary SupplementalUnemploymentBenefitsDisabilityRelatedBenefitsMaximumBenefitProvidedAsRatioOfFinalSalary	0.6666666667	Rate
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CY2018Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	80000000	shares
CY2019Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	80000000	shares
CY2018Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	37845224	shares
CY2019Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	37887662	shares
CY2018Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2018	us-gaap	Dividends Stock DividendsStock	0	USD
CY2018	us-gaap	Employee Stock Ownership Plan Esop Cash Contributions To Esop EmployeeStockOwnershipPlanESOPCashContributionsToESOP	700000	USD
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CY2019	dei	Document Annual Report DocumentAnnualReport	true
CY2019	dei	Document Period End Date DocumentPeriodEndDate	2019-12-31
CY2019	dei	Document Transition Report DocumentTransitionReport	false
CY2019	dei	Entity File Number EntityFileNumber	000-12247
CY2019	dei	Entity Registrant Name EntityRegistrantName	SOUTHSIDE BANCSHARES, INC.
CY2019	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	TX
CY2019	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	75-1848732
CY2019	dei	Entity Address Address Line1 EntityAddressAddressLine1	1201 S. Beckham Avenue,
CY2019	dei	Entity Address City Or Town EntityAddressCityOrTown	Tyler,
CY2019	dei	Entity Address State Or Province EntityAddressStateOrProvince	TX
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CY2019	dei	City Area Code CityAreaCode	903
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CY2019	dei	Security12b Title Security12bTitle	Common Stock, $1.25 par value
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CY2019	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2307000	USD
CY2017	us-gaap	Interest Expense InterestExpense	43504000	USD
CY2019	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	169805000	USD
CY2018	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	172064000	USD
CY2017	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	143970000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	5101000	USD
CY2018	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	8437000	USD
CY2017	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	4675000	USD
CY2019	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	164704000	USD
CY2018	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	163627000	USD
CY2017	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	139295000	USD
CY2019	sbsi	Fee And Commissions Depositor Account FeeAndCommissionsDepositorAccount	26038000	USD
CY2018	sbsi	Fee And Commissions Depositor Account FeeAndCommissionsDepositorAccount	25082000	USD
CY2017	sbsi	Fee And Commissions Depositor Account FeeAndCommissionsDepositorAccount	21785000	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	756000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	-1839000	USD
CY2017	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	625000	USD
CY2019	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	509000	USD
CY2018	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	692000	USD
CY2017	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	1821000	USD
CY2019	sbsi	Fees And Commissions Fiduciary And Trust Activity FeesAndCommissionsFiduciaryAndTrustActivity	6269000	USD
CY2018	sbsi	Fees And Commissions Fiduciary And Trust Activity FeesAndCommissionsFiduciaryAndTrustActivity	6832000	USD
CY2018	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2923000	USD
CY2017	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2537000	USD
CY2019	us-gaap	Brokerage Commissions Revenue BrokerageCommissionsRevenue	2080000	USD
CY2018	us-gaap	Brokerage Commissions Revenue BrokerageCommissionsRevenue	1987000	USD
CY2017	us-gaap	Brokerage Commissions Revenue BrokerageCommissionsRevenue	2422000	USD
CY2019	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	4409000	USD
CY2018	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	5096000	USD
CY2017	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	4465000	USD
CY2019	us-gaap	Noninterest Income NoninterestIncome	42368000	USD
CY2018	us-gaap	Noninterest Income NoninterestIncome	40773000	USD
CY2017	us-gaap	Noninterest Income NoninterestIncome	37473000	USD
CY2019	us-gaap	Labor And Related Expense LaborAndRelatedExpense	73731000	USD
CY2018	us-gaap	Labor And Related Expense LaborAndRelatedExpense	70643000	USD
CY2017	us-gaap	Labor And Related Expense LaborAndRelatedExpense	60779000	USD
CY2019	us-gaap	Occupancy Net OccupancyNet	13128000	USD
CY2018	us-gaap	Occupancy Net OccupancyNet	13814000	USD
CY2017	us-gaap	Occupancy Net OccupancyNet	12068000	USD
CY2019	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	0	USD
CY2018	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	2413000	USD
CY2017	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	4352000	USD
CY2019	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	2964000	USD
CY2018	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	2894000	USD
CY2017	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	2219000	USD
CY2019	sbsi	Atm Expense ATMExpense	894000	USD
CY2018	sbsi	Atm Expense ATMExpense	1090000	USD
CY2017	sbsi	Atm Expense ATMExpense	3889000	USD
CY2019	us-gaap	Professional Fees ProfessionalFees	4717000	USD
CY2018	us-gaap	Professional Fees ProfessionalFees	4035000	USD
CY2017	us-gaap	Professional Fees ProfessionalFees	3844000	USD
CY2019	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	4537000	USD
CY2018	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	3996000	USD
CY2017	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	3027000	USD
CY2019	us-gaap	Communication Communication	1941000	USD
CY2018	us-gaap	Communication Communication	1847000	USD
CY2017	us-gaap	Communication Communication	1905000	USD
CY2019	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	859000	USD
CY2018	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	1871000	USD
CY2017	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	1769000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	4418000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	5213000	USD
CY2017	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1955000	USD
CY2019	us-gaap	Other Noninterest Expense OtherNoninterestExpense	12108000	USD
CY2018	us-gaap	Other Noninterest Expense OtherNoninterestExpense	12283000	USD
CY2017	us-gaap	Other Noninterest Expense OtherNoninterestExpense	10528000	USD
CY2019	us-gaap	Noninterest Expense NoninterestExpense	119297000	USD
CY2018	us-gaap	Noninterest Expense NoninterestExpense	120099000	USD
CY2017	us-gaap	Noninterest Expense NoninterestExpense	106335000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	87775000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	84301000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	70433000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	13221000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10163000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	16121000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	74554000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	74138000	USD
CY2017	us-gaap	Profit Loss ProfitLoss	54312000	USD
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.21
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.12
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.82
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.20
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.11
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.81
CY2019	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.26
CY2018	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.20
CY2017	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.11
CY2019	us-gaap	Net Income Loss NetIncomeLoss	74554000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	74138000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	54312000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	87481000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-34238000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	15217000	USD
CY2019	us-gaap	Other Comprehensive Income Reclassification Adjustment For Held To Maturity Transferred To Available For Sale Securities Before Tax OtherComprehensiveIncomeReclassificationAdjustmentForHeldToMaturityTransferredToAvailableForSaleSecuritiesBeforeTax	0	USD
CY2018	us-gaap	Other Comprehensive Income Reclassification Adjustment For Held To Maturity Transferred To Available For Sale Securities Before Tax OtherComprehensiveIncomeReclassificationAdjustmentForHeldToMaturityTransferredToAvailableForSaleSecuritiesBeforeTax	11881000	USD
CY2017	us-gaap	Other Comprehensive Income Reclassification Adjustment For Held To Maturity Transferred To Available For Sale Securities Before Tax OtherComprehensiveIncomeReclassificationAdjustmentForHeldToMaturityTransferredToAvailableForSaleSecuritiesBeforeTax	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Reclassification Adjustments And Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsAndTax	0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Reclassification Adjustments And Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsAndTax	401000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Reclassification Adjustments And Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsAndTax	0	USD
CY2019	sbsi	Amortizationof Unrealized Gains Losseson Securities Transferred Between Availablefor Sale And Heldto Maturity Debt Securities Before Tax AmortizationofUnrealizedGainsLossesonSecuritiesTransferredBetweenAvailableforSaleAndHeldtoMaturityDebtSecuritiesBeforeTax	-816000	USD
CY2018	sbsi	Amortizationof Unrealized Gains Losseson Securities Transferred Between Availablefor Sale And Heldto Maturity Debt Securities Before Tax AmortizationofUnrealizedGainsLossesonSecuritiesTransferredBetweenAvailableforSaleAndHeldtoMaturityDebtSecuritiesBeforeTax	-1244000	USD
CY2017	sbsi	Amortizationof Unrealized Gains Losseson Securities Transferred Between Availablefor Sale And Heldto Maturity Debt Securities Before Tax AmortizationofUnrealizedGainsLossesonSecuritiesTransferredBetweenAvailableforSaleAndHeldtoMaturityDebtSecuritiesBeforeTax	-1255000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	756000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-1839000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	625000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	-9118000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	2351000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	3000	USD
CY2019	sbsi	Other Comprehensive Income Unrealized Gain Loss On Terminated Derivatives During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnTerminatedDerivativesDuringPeriodBeforeTax	0	USD
CY2018	sbsi	Other Comprehensive Income Unrealized Gain Loss On Terminated Derivatives During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnTerminatedDerivativesDuringPeriodBeforeTax	0	USD
CY2017	sbsi	Other Comprehensive Income Unrealized Gain Loss On Terminated Derivatives During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnTerminatedDerivativesDuringPeriodBeforeTax	273000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	2043000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	1406000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	-754000	USD
CY2019	sbsi	Other Comprehensive Income Loss Defined Benefit Plan Gain Lossand Prior Service Cost Credit Reclassification Adjustmentfrom Aoc Ibefore Tax OtherComprehensiveIncomeLossDefinedBenefitPlanGainLossandPriorServiceCostCreditReclassificationAdjustmentfromAOCIbeforeTax	2378000	USD
CY2018	sbsi	Other Comprehensive Income Loss Defined Benefit Plan Gain Lossand Prior Service Cost Credit Reclassification Adjustmentfrom Aoc Ibefore Tax OtherComprehensiveIncomeLossDefinedBenefitPlanGainLossandPriorServiceCostCreditReclassificationAdjustmentfromAOCIbeforeTax	2182000	USD
CY2017	sbsi	Other Comprehensive Income Loss Defined Benefit Plan Gain Lossand Prior Service Cost Credit Reclassification Adjustmentfrom Aoc Ibefore Tax OtherComprehensiveIncomeLossDefinedBenefitPlanGainLossandPriorServiceCostCreditReclassificationAdjustmentfromAOCIbeforeTax	1605000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Finalization Of Pension And Non Pension Postretirement Plan Valuation Before Tax OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax	0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Finalization Of Pension And Non Pension Postretirement Plan Valuation Before Tax OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax	0	USD
CY2017	us-gaap	Other Comprehensive Income Loss Finalization Of Pension And Non Pension Postretirement Plan Valuation Before Tax OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax	8000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-9816000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-17740000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	68942000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-1994000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-5218000	USD
CY2018Q1	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest Adjusted Balance1 StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1	754140000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	74138000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	13272000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	14478000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-3725000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	5374000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	54464000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-14015000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	7898000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	129018000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	60123000	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	62210000	USD
CY2016Q4	us-gaap	Stockholders Equity StockholdersEquity	518274000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	54312000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	7898000	USD
CY2017	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	1483000	USD
CY2017	us-gaap	Stock Issued During Period Value Acquisitions StockIssuedDuringPeriodValueAcquisitions	200087000	USD
CY2017	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	1815000	USD
CY2017	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	2470000	USD
CY2017	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	32199000	USD
CY2017	us-gaap	Dividends Common Stock Stock DividendsCommonStockStock	0	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	754140000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-14015000	USD
CY2018	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	1478000	USD
CY2018	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	47193000	USD
CY2018	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	2317000	USD
CY2018	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	2405000	USD
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	41979000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	731291000	USD
CY2019Q1	us-gaap	Cumulative Effect Of New Accounting Principle In Period Of Adoption CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	-16452000	USD
CY2019Q1	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest Adjusted Balance1 StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1	714839000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	74554000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	54464000	USD
CY2019	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	1445000	USD
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	2181000	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	2388000	USD
CY2019	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	1592000	USD
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	42521000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	804580000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	74554000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	74138000	USD
CY2018	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	8437000	USD
CY2017	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	4675000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	2388000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	2317000	USD
CY2017	us-gaap	Share Based Compensation ShareBasedCompensation	1815000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	122000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	6154000	USD
CY2017	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	3514000	USD
CY2017	us-gaap	Profit Loss ProfitLoss	54312000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	12111000	USD
CY2018	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	14045000	USD
CY2017	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	10208000	USD
CY2019	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-13874000	USD
CY2018	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-13675000	USD
CY2017	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-17639000	USD
CY2019	us-gaap	Investment Income Net Amortization Of Discount And Premium InvestmentIncomeNetAmortizationOfDiscountAndPremium	1211000	USD
CY2018	us-gaap	Investment Income Net Amortization Of Discount And Premium InvestmentIncomeNetAmortizationOfDiscountAndPremium	2333000	USD
CY2017	us-gaap	Investment Income Net Amortization Of Discount And Premium InvestmentIncomeNetAmortizationOfDiscountAndPremium	1142000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	5101000	USD
CY2019	us-gaap	Availableforsale Securities Gross Realized Gain Loss Excluding Other Than Temporary Impairments AvailableforsaleSecuritiesGrossRealizedGainLossExcludingOtherThanTemporaryImpairments	756000	USD
CY2018	us-gaap	Availableforsale Securities Gross Realized Gain Loss Excluding Other Than Temporary Impairments AvailableforsaleSecuritiesGrossRealizedGainLossExcludingOtherThanTemporaryImpairments	-1839000	USD
CY2017	us-gaap	Availableforsale Securities Gross Realized Gain Loss Excluding Other Than Temporary Impairments AvailableforsaleSecuritiesGrossRealizedGainLossExcludingOtherThanTemporaryImpairments	625000	USD
CY2019	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	-592000	USD
CY2018	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	-768000	USD
CY2017	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	-152000	USD
CY2019	us-gaap	Proceeds From Sale Of Mortgage Loans Held For Sale ProceedsFromSaleOfMortgageLoansHeldForSale	22041000	USD
CY2018	us-gaap	Proceeds From Sale Of Mortgage Loans Held For Sale ProceedsFromSaleOfMortgageLoansHeldForSale	24092000	USD
CY2017	us-gaap	Proceeds From Sale Of Mortgage Loans Held For Sale ProceedsFromSaleOfMortgageLoansHeldForSale	58747000	USD
CY2019	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	21823000	USD
CY2018	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	22692000	USD
CY2017	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	53107000	USD
CY2019	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	100000	USD
CY2018	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	-433000	USD
CY2017	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	-7000	USD
CY2019	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	0	USD
CY2018	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	124000	USD
CY2017	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	0	USD
CY2019	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	1165000	USD
CY2018	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	-1204000	USD
CY2017	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	63000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	12275000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	2166000	USD
CY2017	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	3909000	USD
CY2019	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	530000	USD
CY2018	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	1257000	USD
CY2017	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	570000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-13377000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	1358000	USD
CY2017	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-1063000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	80606000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	122402000	USD
CY2017	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	91730000	USD
CY2019	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	1253139000	USD
CY2018	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	306867000	USD
CY2017	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	619398000	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	751116000	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	428518000	USD
CY2017	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	685152000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	201529000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	137883000	USD
CY2017	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	113183000	USD
CY2019	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	0	USD
CY2018	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	0	USD
CY2017	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	6260000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	27833000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	3064000	USD
CY2017	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	28974000	USD
CY2019	us-gaap	Proceeds From Sale Of Federal Reserve Stock ProceedsFromSaleOfFederalReserveStock	8788000	USD
CY2018	us-gaap	Proceeds From Sale Of Federal Reserve Stock ProceedsFromSaleOfFederalReserveStock	24360000	USD
CY2017	us-gaap	Proceeds From Sale Of Federal Reserve Stock ProceedsFromSaleOfFederalReserveStock	6945000	USD
CY2019	us-gaap	Payments To Acquire Federal Reserve Stock PaymentsToAcquireFederalReserveStock	26483000	USD
CY2018	us-gaap	Payments To Acquire Federal Reserve Stock PaymentsToAcquireFederalReserveStock	1518000	USD
CY2017	us-gaap	Payments To Acquire Federal Reserve Stock PaymentsToAcquireFederalReserveStock	1233000	USD
CY2019	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	262137000	USD
CY2018	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	24491000	USD
CY2017	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	117750000	USD
CY2019	us-gaap	Proceeds From Sale Of Loans Receivable ProceedsFromSaleOfLoansReceivable	0	USD
CY2018	us-gaap	Proceeds From Sale Of Loans Receivable ProceedsFromSaleOfLoansReceivable	4300000	USD
CY2017	us-gaap	Proceeds From Sale Of Loans Receivable ProceedsFromSaleOfLoansReceivable	0	USD
CY2019	us-gaap	Cash Acquired From Acquisition CashAcquiredFromAcquisition	0	USD
CY2019	us-gaap	Cash Acquired From Acquisition CashAcquiredFromAcquisition	0	USD
CY2017	us-gaap	Cash Acquired From Acquisition CashAcquiredFromAcquisition	115598000	USD
CY2019	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	0	USD
CY2019	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	0	USD
CY2017	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	23941000	USD
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	15883000	USD
CY2018	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	13444000	USD
CY2017	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	9633000	USD
CY2019	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
CY2018	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	5956000	USD
CY2017	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
CY2019	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	96000	USD
CY2018	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	1943000	USD
CY2017	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	12000	USD
CY2019	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	1122000	USD
CY2018	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	1717000	USD
CY2017	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	659000	USD
CY2019	us-gaap	Proceeds From Sale Of Foreclosed Assets ProceedsFromSaleOfForeclosedAssets	328000	USD
CY2018	us-gaap	Proceeds From Sale Of Foreclosed Assets ProceedsFromSaleOfForeclosedAssets	483000	USD
CY2017	us-gaap	Proceeds From Sale Of Foreclosed Assets ProceedsFromSaleOfForeclosedAssets	429000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-566830000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	261904000	USD
CY2017	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	172737000	USD
CY2019	us-gaap	Net Change Interest And Noninterest Bearing Deposits Domestic NetChangeInterestAndNoninterestBearingDepositsDomestic	272638000	USD
CY2018	us-gaap	Net Change Interest And Noninterest Bearing Deposits Domestic NetChangeInterestAndNoninterestBearingDepositsDomestic	-106014000	USD
CY2017	us-gaap	Net Change Interest And Noninterest Bearing Deposits Domestic NetChangeInterestAndNoninterestBearingDepositsDomestic	82960000	USD
CY2019	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	-8452000	USD
CY2018	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	27312000	USD
CY2017	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	2401000	USD
CY2019	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	6914800000	USD
CY2018	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	4201500000	USD
CY2017	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	2786476000	USD
CY2019	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	6661119000	USD
CY2018	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	4499788000	USD
CY2017	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	3078743000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	1986000	USD
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	2653000	USD
CY2017	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	2692000	USD
CY2019	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	394000	USD
CY2018	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	248000	USD
CY2017	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	222000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	2181000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	47193000	USD
CY2017	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	USD
CY2019	us-gaap	Proceeds From Issuance Of Common Stock Dividend Reinvestment Plan ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	1445000	USD
CY2018	us-gaap	Proceeds From Issuance Of Common Stock Dividend Reinvestment Plan ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	1478000	USD
CY2017	us-gaap	Proceeds From Issuance Of Common Stock Dividend Reinvestment Plan ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	1483000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	42521000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	41979000	USD
CY2017	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	32199000	USD
CY2019	us-gaap	Payments Of Merger Related Costs Financing Activities PaymentsOfMergerRelatedCostsFinancingActivities	0	USD
CY2018	us-gaap	Payments Of Merger Related Costs Financing Activities PaymentsOfMergerRelatedCostsFinancingActivities	0	USD
CY2017	us-gaap	Payments Of Merger Related Costs Financing Activities PaymentsOfMergerRelatedCostsFinancingActivities	277000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	476202000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-462279000	USD
CY2017	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-235429000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-10022000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-77973000	USD
CY2017	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	29038000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	120719000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	198692000	USD
CY2016Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	169654000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	110697000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	120719000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	198692000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	70452000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	55844000	USD
CY2017	us-gaap	Interest Paid Net InterestPaidNet	42934000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	10500000	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	2000000	USD
CY2017	us-gaap	Income Taxes Paid IncomeTaxesPaid	11300000	USD
CY2019	sbsi	Loans Transferred To Other Repossessed Assets And Real Estate Through Foreclosure LoansTransferredToOtherRepossessedAssetsAndRealEstateThroughForeclosure	649000	USD
CY2018	sbsi	Loans Transferred To Other Repossessed Assets And Real Estate Through Foreclosure LoansTransferredToOtherRepossessedAssetsAndRealEstateThroughForeclosure	2128000	USD
CY2017	sbsi	Loans Transferred To Other Repossessed Assets And Real Estate Through Foreclosure LoansTransferredToOtherRepossessedAssetsAndRealEstateThroughForeclosure	574000	USD
CY2019	us-gaap	Transfer Of Portfolio Loans And Leases To Held For Sale1 TransferOfPortfolioLoansAndLeasesToHeldForSale1	0	USD
CY2018	us-gaap	Transfer Of Portfolio Loans And Leases To Held For Sale1 TransferOfPortfolioLoansAndLeasesToHeldForSale1	3984000	USD
CY2017	us-gaap	Transfer Of Portfolio Loans And Leases To Held For Sale1 TransferOfPortfolioLoansAndLeasesToHeldForSale1	0	USD
CY2019	us-gaap	Debt Securities Held To Maturity Transfer Amount DebtSecuritiesHeldToMaturityTransferAmount	0	USD
CY2018	us-gaap	Debt Securities Held To Maturity Transfer Amount DebtSecuritiesHeldToMaturityTransferAmount	743421000	USD
CY2017	us-gaap	Debt Securities Held To Maturity Transfer Amount DebtSecuritiesHeldToMaturityTransferAmount	0	USD
CY2019	us-gaap	Dividends Stock DividendsStock	0	USD
CY2018	us-gaap	Dividends Stock DividendsStock	0	USD
CY2017	us-gaap	Dividends Stock DividendsStock	24960000	USD
CY2019Q4	sbsi	Unsettled Trades To Purchase Securities Liability UnsettledTradesToPurchaseSecuritiesLiability	17538000	USD
CY2018Q4	sbsi	Unsettled Trades To Purchase Securities Liability UnsettledTradesToPurchaseSecuritiesLiability	6378000	USD
CY2017Q4	sbsi	Unsettled Trades To Purchase Securities Liability UnsettledTradesToPurchaseSecuritiesLiability	0	USD
CY2019Q4	sbsi	Unsettled Issuancesof Brokered C Ds UnsettledIssuancesofBrokeredCDs	20000000	USD
CY2018Q4	sbsi	Unsettled Issuancesof Brokered C Ds UnsettledIssuancesofBrokeredCDs	15236000	USD
CY2017Q4	sbsi	Unsettled Issuancesof Brokered C Ds UnsettledIssuancesofBrokeredCDs	0	USD
CY2019	us-gaap	Business Combination Consideration Transferred Equity Interests Issued And Issuable BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable	0	USD
CY2018	us-gaap	Business Combination Consideration Transferred Equity Interests Issued And Issuable BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable	0	USD
CY2017	us-gaap	Business Combination Consideration Transferred Equity Interests Issued And Issuable BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable	200364000	USD
CY2019Q4	sbsi	Numberofbankingcenters Numberofbankingcenters	60	banking_offices
CY2019Q4	sbsi	Numberofbankingcentersingrocerystores Numberofbankingcentersingrocerystores	16	banking_offices
CY2019	us-gaap	Dividends Stock DividendsStock	0	USD
CY2017	sbsi	Stock Dividends Percentage Of Common Stock StockDividendsPercentageOfCommonStock	0.025	Rate
CY2019	us-gaap	Use Of Estimates UseOfEstimates	<div style="line-height:120%;padding-bottom:8px;padding-top:8px;text-align:justify;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;text-decoration:underline;">Use of Estimates</span><span style="font-family:inherit;font-size:10pt;">. In preparing consolidated financial statements in conformity with GAAP, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheet and reported amounts of revenues and expenses during the reporting period. These estimates are subjective in nature and involve matters of judgment. Actual results could differ from these estimates. Material estimates that are particularly susceptible to significant change in the near term relate to the determination of the allowance for loan losses, assumptions used in the defined benefit plan and the fair values of financial instruments. The status of contingencies are particularly subject to change and significant assumptions used in periodic evaluation of securities for other-than-temporary impairment. </span></div>
CY2019	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	1	segment
CY2019Q4	us-gaap	Cash Reserve Deposit Required And Made CashReserveDepositRequiredAndMade	33800000	USD
CY2018Q4	us-gaap	Cash Reserve Deposit Required And Made CashReserveDepositRequiredAndMade	34100000	USD
CY2018	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2019	sbsi	Goodwill Impairmentlosscumulative GoodwillImpairmentlosscumulative	0	USD
CY2019	us-gaap	Derivatives Hedge Discontinuances Termination Of Hedging Instrument Or Hedged Item DerivativesHedgeDiscontinuancesTerminationOfHedgingInstrumentOrHedgedItem	<div style="line-height:120%;padding-top:8px;text-align:justify;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;text-decoration:underline;">Terminated Derivative Financial Instruments</span><span style="font-family:inherit;font-size:10pt;">. In accordance with ASC Topic 815, if a hedging item is terminated prior to maturity for a cash settlement, the existing gain or loss within AOCI will continue to be reclassified into earnings during the period or periods in which the hedged forecasted transaction affects earnings unless it is probable that the forecasted transaction will not occur by the end of the originally specified time period. If the forecasted transaction is deemed probable to not occur, the derivative gain or loss reported in AOCI shall be reclassified into earnings immediately. During the first quarter of 2017, we terminated </span><span style="font-family:inherit;font-size:10pt;"><span>two</span></span><span style="font-family:inherit;font-size:10pt;"> interest rate swap contracts designated as cash flow hedges. At the time of termination, we determined the underlying hedged forecasted transactions were still probable of occurring. These transactions are reevaluated on a monthly basis to determine if the hedged forecasted transactions are still probable of occurring. If at a subsequent evaluation it is determined that the transactions will not occur, any related gains or losses recorded in AOCI are immediately recognized in earnings.</span></div>
CY2018Q4	us-gaap	Goodwill Goodwill	201116000	USD
CY2017Q4	us-gaap	Goodwill Goodwill	201246000	USD
CY2019	us-gaap	Goodwill Purchase Accounting Adjustments GoodwillPurchaseAccountingAdjustments	0	USD
CY2018	us-gaap	Goodwill Purchase Accounting Adjustments GoodwillPurchaseAccountingAdjustments	-130000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	201116000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	201116000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	74554000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	74138000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	54312000	USD
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	33747000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	34951000	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	29841000	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	148000	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	165000	shares
CY2017	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	206000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	33895000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	35116000	shares
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	30047000	shares
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.21
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.12
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.82
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.20
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.11
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.81
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	521000	shares
CY2018	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	356000	shares
CY2017	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	154000	shares
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	2358597000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	134863000	USD
CY2019	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-313000	USD
CY2018	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-3048000	USD
CY2017	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-1943000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	2306741000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	54426000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	2570000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	4238000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	222000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	138879000	USD
CY2018Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	2013485000	USD
CY2018Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	10554000	USD
CY2018Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	34603000	USD
CY2018Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	1989436000	USD
CY2018Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	162931000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	360000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	3510000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	159781000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	273963000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	2282000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	30697000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	288000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	304660000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	2570000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	13053000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	76000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	4092000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	146000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue	17145000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	222000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	115902000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	1247000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	1345243000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	33356000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	1461145000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	34603000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	5460000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	63000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	142236000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	3447000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue	147696000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	3510000	USD
CY2019Q4	sbsi	Af Ssecuritiesand Ht Msecuritieswithotherthantemporaryimpairment AFSsecuritiesandHTMsecuritieswithotherthantemporaryimpairment	0
CY2019Q4	sbsi	Transferred Securities Unrealized Loss Before Tax TransferredSecuritiesUnrealizedLossBeforeTax	3700000	USD
CY2019Q4	sbsi	Securitiestransferred Unrealized Loss Netof Tax SecuritiestransferredUnrealizedLossNetofTax	2900000	USD
CY2018Q4	sbsi	Transferred Securities Unrealized Loss Before Tax TransferredSecuritiesUnrealizedLossBeforeTax	15300000	USD
CY2018Q4	sbsi	Securitiestransferred Unrealized Loss Netof Tax SecuritiestransferredUnrealizedLossNetofTax	12100000	USD
CY2019	sbsi	Securities Transferred From Available For Sale To Held To Maturity SecuritiesTransferredFromAvailableForSaleToHeldToMaturity	0	USD
CY2019	us-gaap	Interest Income Securities Us Treasury InterestIncomeSecuritiesUSTreasury	0	USD
CY2018	us-gaap	Interest Income Securities Us Treasury InterestIncomeSecuritiesUSTreasury	218000	USD
CY2017	us-gaap	Interest Income Securities Us Treasury InterestIncomeSecuritiesUSTreasury	519000	USD
CY2019	us-gaap	Interest Income Securities Other Us Government InterestIncomeSecuritiesOtherUSGovernment	0	USD
CY2018	us-gaap	Interest Income Securities Other Us Government InterestIncomeSecuritiesOtherUSGovernment	89000	USD
CY2017	us-gaap	Interest Income Securities Other Us Government InterestIncomeSecuritiesOtherUSGovernment	178000	USD
CY2019	us-gaap	Interest Income Securities State And Municipal InterestIncomeSecuritiesStateAndMunicipal	16885000	USD
CY2018	us-gaap	Interest Income Securities State And Municipal InterestIncomeSecuritiesStateAndMunicipal	24960000	USD
CY2017	us-gaap	Interest Income Securities State And Municipal InterestIncomeSecuritiesStateAndMunicipal	24530000	USD
CY2019	sbsi	Interest Income Other Stocks And Bonds InterestIncomeOtherStocksAndBonds	138000	USD
CY2018	sbsi	Interest Income Other Stocks And Bonds InterestIncomeOtherStocksAndBonds	110000	USD
CY2017	sbsi	Interest Income Other Stocks And Bonds InterestIncomeOtherStocksAndBonds	125000	USD
CY2019	sbsi	Interestincome Other Equity Securities InterestincomeOtherEquitySecurities	0	USD
CY2018	sbsi	Interestincome Other Equity Securities InterestincomeOtherEquitySecurities	0	USD
CY2017	sbsi	Interestincome Other Equity Securities InterestincomeOtherEquitySecurities	116000	USD
CY2019	us-gaap	Interest Income Securities Mortgage Backed InterestIncomeSecuritiesMortgageBacked	50486000	USD
CY2018	us-gaap	Interest Income Securities Mortgage Backed InterestIncomeSecuritiesMortgageBacked	41584000	USD
CY2017	us-gaap	Interest Income Securities Mortgage Backed InterestIncomeSecuritiesMortgageBacked	41361000	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	756000	USD
CY2019	us-gaap	Interest And Other Income InterestAndOtherIncome	67509000	USD
CY2018	us-gaap	Interest And Other Income InterestAndOtherIncome	66961000	USD
CY2017	us-gaap	Interest And Other Income InterestAndOtherIncome	66829000	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	5700000	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	4900000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	-1800000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	3800000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	2000000.0	USD
CY2017	us-gaap	Available For Sale Securities Gross Realized Gain Loss Net AvailableForSaleSecuritiesGrossRealizedGainLossNet	625000	USD
CY2017	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	5000000.0	USD
CY2017	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	4400000	USD
CY2019	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	0	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	1268000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	1269000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	9140000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	9295000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	40606000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	42079000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	739362000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	760296000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Single Maturity Date Amortized Cost Basis AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis	790376000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Single Maturity Date AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate	812939000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Without Single Maturity Date Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost	1516365000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Without Single Maturity Date Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue	1545658000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	2306741000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	2358597000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	115000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	116000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	1663000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	1678000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	1110000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	1124000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	0	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	0	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Single Maturity Date Amortized Cost Basis HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis	2888000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Single Maturity Date Fair Value HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValue	2918000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Without Single Maturity Date Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithoutSingleMaturityDateNetCarryingAmount	131975000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Without Single Maturity Date Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue	135961000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	134863000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	138879000	USD
CY2019Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Securities Pledged PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesPledged	1120000000	USD
CY2018Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Securities Pledged PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesPledged	1080000000.00	USD
CY2019Q4	us-gaap	Equity Securities Fv Ni And Without Readily Determinable Fair Value EquitySecuritiesFvNiAndWithoutReadilyDeterminableFairValue	12300000	USD
CY2018Q4	us-gaap	Equity Securities Fv Ni And Without Readily Determinable Fair Value EquitySecuritiesFvNiAndWithoutReadilyDeterminableFairValue	12100000	USD
CY2019	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	66000	USD
CY2018	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	-117000	USD
CY2019	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	0	USD
CY2018	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	0	USD
CY2019	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	66000	USD
CY2018	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	-117000	USD
CY2019Q4	sbsi	Equityinvestmentswithotherthantemporaryimpairment Equityinvestmentswithotherthantemporaryimpairment	0
CY2019Q4	sbsi	Federal Home Loan Bankstockwithotherthantemporaryimpairment FederalHomeLoanBankstockwithotherthantemporaryimpairment	0
CY2019Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3568204000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3312799000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	24797000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	27019000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	3543407000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	3285780000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	4800000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	4000000.0	USD
CY2019Q4	sbsi	Loans And Leases Receivable Related Parties As Percent Of Shareholders Equity LoansAndLeasesReceivableRelatedPartiesAsPercentOfShareholdersEquity	0.006	Rate
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	27019000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	5101000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	8933000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	1610000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	24797000	USD
CY2017Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	20781000	USD
CY2018	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	8437000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	4246000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	2047000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	27019000	USD
CY2016Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	17911000	USD
CY2017	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	4675000	USD
CY2017	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	3453000	USD
CY2017	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	1648000	USD
CY2017Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	20781000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	5100000	USD
CY2019	sbsi	Provisionfor Pci Loans ProvisionforPCILoans	-45000	USD
CY2018	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	8400000	USD
CY2018	sbsi	Provisionfor Pci Loans ProvisionforPCILoans	302000	USD
CY2017	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	4700000	USD
CY2017	sbsi	Provisionfor Pci Loans ProvisionforPCILoans	0	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	1114000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	23683000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	24797000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	5908000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	21111000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	27019000	USD
CY2019Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	13460000	USD
CY2019Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	3516937000	USD
CY2019Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet	37807000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3568204000	USD
CY2018Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	36247000	USD
CY2018Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	3230150000	USD
CY2018Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet	46402000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3312799000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3568204000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3312799000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	4963000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	35770000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	0	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	0	USD
CY2019Q4	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	12014000	USD
CY2018Q4	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	5930000	USD
CY2019Q4	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	472000	USD
CY2018Q4	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	1206000	USD
CY2019Q4	us-gaap	Other Foreclosed Assets OtherForeclosedAssets	0	USD
CY2018Q4	us-gaap	Other Foreclosed Assets OtherForeclosedAssets	0	USD
CY2019Q4	sbsi	Nonperforming Assets NonperformingAssets	17449000	USD
CY2018Q4	sbsi	Nonperforming Assets NonperformingAssets	42906000	USD
CY2019Q4	sbsi	Restructured Nonaccrual Loans RestructuredNonaccrualLoans	469000	USD
CY2018Q4	sbsi	Restructured Nonaccrual Loans RestructuredNonaccrualLoans	10900000	USD
CY2019Q4	sbsi	Purchase Credit Impaired Loans Restructured PurchaseCreditImpairedLoansRestructured	755000	USD
CY2018Q4	sbsi	Purchase Credit Impaired Loans Restructured PurchaseCreditImpairedLoansRestructured	3100000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	4963000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	35770000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	0	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Unpaid Principal Balance ImpairedFinancingReceivableUnpaidPrincipalBalance	27871000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	20185000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	1114000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable Unpaid Principal Balance ImpairedFinancingReceivableUnpaidPrincipalBalance	47274000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	44267000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	5908000	USD
CY2019Q4	sbsi	Purchase Credit Impaired Loanswith Deteriorationin Credit Quality After Acquisition PurchaseCreditImpairedLoanswithDeteriorationinCreditQualityAfterAcquisition	6700000	USD
CY2018Q4	sbsi	Purchase Credit Impaired Loanswith Deteriorationin Credit Quality After Acquisition PurchaseCreditImpairedLoanswithDeteriorationinCreditQualityAfterAcquisition	8000000.0	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	19203000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	3549001000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3568204000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	34314000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	3278485000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3312799000	USD
CY2019	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	36758000	USD
CY2019	us-gaap	Impaired Financing Receivable Interest Income Cash Basis Method ImpairedFinancingReceivableInterestIncomeCashBasisMethod	1271000	USD
CY2018	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	33383000	USD
CY2018	us-gaap	Impaired Financing Receivable Interest Income Cash Basis Method ImpairedFinancingReceivableInterestIncomeCashBasisMethod	417000	USD
CY2017	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	9504000	USD
CY2017	us-gaap	Impaired Financing Receivable Interest Income Cash Basis Method ImpairedFinancingReceivableInterestIncomeCashBasisMethod	325000	USD
CY2019	sbsi	Loan Modification Related To Extending Amortization Period LoanModificationRelatedToExtendingAmortizationPeriod	7574000	USD
CY2019	sbsi	Loanmodificationrelatedtointerestratesreductions Loanmodificationrelatedtointerestratesreductions	0	USD
CY2019	sbsi	Loan Modification Extending Amortization Period Lowering Interest Rate And Principal Forgiveness LoanModificationExtendingAmortizationPeriodLoweringInterestRateAndPrincipalForgiveness	1381000	USD
CY2019	sbsi	Financing Receivable Modifications Total Modifications For Period FinancingReceivableModificationsTotalModificationsForPeriod	8955000	USD
CY2019	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	18	contract
CY2018	sbsi	Loan Modification Related To Extending Amortization Period LoanModificationRelatedToExtendingAmortizationPeriod	10617000	USD
CY2018	sbsi	Loanmodificationrelatedtointerestratesreductions Loanmodificationrelatedtointerestratesreductions	112000	USD
CY2018	sbsi	Loan Modification Extending Amortization Period Lowering Interest Rate And Principal Forgiveness LoanModificationExtendingAmortizationPeriodLoweringInterestRateAndPrincipalForgiveness	540000	USD
CY2018	sbsi	Financing Receivable Modifications Total Modifications For Period FinancingReceivableModificationsTotalModificationsForPeriod	11269000	USD
CY2018	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	22	contract
CY2017	sbsi	Loan Modification Related To Extending Amortization Period LoanModificationRelatedToExtendingAmortizationPeriod	801000	USD
CY2017	sbsi	Loanmodificationrelatedtointerestratesreductions Loanmodificationrelatedtointerestratesreductions	0	USD
CY2017	sbsi	Loan Modification Extending Amortization Period Lowering Interest Rate And Principal Forgiveness LoanModificationExtendingAmortizationPeriodLoweringInterestRateAndPrincipalForgiveness	293000	USD
CY2017	sbsi	Financing Receivable Modifications Total Modifications For Period FinancingReceivableModificationsTotalModificationsForPeriod	1094000	USD
CY2017	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	10	contract
CY2019Q4	sbsi	Loans Receivable Modifications Commitmentto Lend LoansReceivableModificationsCommitmenttoLend	0	USD
CY2019Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Outstanding Balance CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesOutstandingBalance	41858000	USD
CY2018Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Outstanding Balance CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesOutstandingBalance	51388000	USD
CY2019Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet	37807000	USD
CY2018Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet	46402000	USD
CY2019Q4	us-gaap	Furniture And Fixtures Gross FurnitureAndFixturesGross	44647000	USD
CY2018Q4	us-gaap	Furniture And Fixtures Gross FurnitureAndFixturesGross	41810000	USD
CY2018Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	15054000	USD
CY2017Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	18721000	USD
CY2016Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	2480000	USD
CY2019	sbsi	Certain Loans Acquiredin Transfer Not Accountedforas Debt Securities Accretable Yield Acquired CertainLoansAcquiredinTransferNotAccountedforasDebtSecuritiesAccretableYieldAcquired	0	USD
CY2018	sbsi	Certain Loans Acquiredin Transfer Not Accountedforas Debt Securities Accretable Yield Acquired CertainLoansAcquiredinTransferNotAccountedforasDebtSecuritiesAccretableYieldAcquired	0	USD
CY2017	sbsi	Certain Loans Acquiredin Transfer Not Accountedforas Debt Securities Accretable Yield Acquired CertainLoansAcquiredinTransferNotAccountedforasDebtSecuritiesAccretableYieldAcquired	15389000	USD
CY2019	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Period Increase Decrease CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldPeriodIncreaseDecrease	0	USD
CY2018	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Period Increase Decrease CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldPeriodIncreaseDecrease	-1445000	USD
CY2017	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Period Increase Decrease CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldPeriodIncreaseDecrease	0	USD
CY2019	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Reclassifications To From Nonaccretable Difference CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldReclassificationsToFromNonaccretableDifference	1354000	USD
CY2018	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Reclassifications To From Nonaccretable Difference CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldReclassificationsToFromNonaccretableDifference	1211000	USD
CY2017	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Reclassifications To From Nonaccretable Difference CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldReclassificationsToFromNonaccretableDifference	1720000	USD
CY2019	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	2988000	USD
CY2018	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	3433000	USD
CY2017	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	868000	USD
CY2019Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	13420000	USD
CY2018Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	15054000	USD
CY2017Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	18721000	USD
CY2019Q4	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	176949000	USD
CY2018Q4	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	166128000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	221596000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	207938000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	77684000	USD
CY2018Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	71966000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	143912000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	135972000	USD
CY2019	us-gaap	Accumulated Depreciation Depletion And Amortization Sale Of Property Plant And Equipment1 AccumulatedDepreciationDepletionAndAmortizationSaleOfPropertyPlantAndEquipment1	1500000	USD
CY2018	us-gaap	Accumulated Depreciation Depletion And Amortization Sale Of Property Plant And Equipment1 AccumulatedDepreciationDepletionAndAmortizationSaleOfPropertyPlantAndEquipment1	2200000	USD
CY2019	us-gaap	Depreciation Depreciation	7300000	USD
CY2018	us-gaap	Depreciation Depreciation	8400000	USD
CY2017	us-gaap	Depreciation Depreciation	8100000	USD
CY2019Q4	us-gaap	Noninterest Bearing Deposit Liabilities Domestic NoninterestBearingDepositLiabilitiesDomestic	1040112000	USD
CY2018Q4	us-gaap	Noninterest Bearing Deposit Liabilities Domestic NoninterestBearingDepositLiabilitiesDomestic	994680000	USD
CY2019Q4	us-gaap	Interest Bearing Deposit Liabilities Domestic InterestBearingDepositLiabilitiesDomestic	3662657000	USD
CY2018Q4	us-gaap	Interest Bearing Deposit Liabilities Domestic InterestBearingDepositLiabilitiesDomestic	3430350000	USD
CY2019Q4	us-gaap	Deposits Deposits	4702769000	USD
CY2018Q4	us-gaap	Deposits Deposits	4425030000	USD
CY2019	sbsi	Interest Expense Time Deposits250000or More InterestExpenseTimeDeposits250000orMore	7600000	USD
CY2018	sbsi	Interest Expense Time Deposits250000or More InterestExpenseTimeDeposits250000orMore	8500000	USD
CY2017	sbsi	Interest Expense Time Deposits250000or More InterestExpenseTimeDeposits250000orMore	5000000.0	USD
CY2019Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	1124655000	USD
CY2019Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	98530000	USD
CY2019Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	29281000	USD
CY2019Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	24319000	USD
CY2019Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	11100000	USD
CY2019Q4	us-gaap	Time Deposit Maturities After Year Five TimeDepositMaturitiesAfterYearFive	5783000	USD
CY2019Q4	us-gaap	Time Deposits TimeDeposits	1293668000	USD
CY2019Q4	us-gaap	Related Party Deposit Liabilities RelatedPartyDepositLiabilities	9900000	USD
CY2018Q4	us-gaap	Related Party Deposit Liabilities RelatedPartyDepositLiabilities	16200000	USD
CY2019Q4	us-gaap	Deposit Liabilities Reclassified As Loans Receivable1 DepositLiabilitiesReclassifiedAsLoansReceivable1	1700000	USD
CY2018Q4	us-gaap	Deposit Liabilities Reclassified As Loans Receivable1 DepositLiabilitiesReclassifiedAsLoansReceivable1	1600000	USD
CY2019Q4	sbsi	Borrowed Funds Maturities Repaymentsof Principalinthe Next Twelve Months BorrowedFundsMaturitiesRepaymentsofPrincipalintheNextTwelveMonths	985374000	USD
CY2019Q4	sbsi	Borrowed Funds Maturingin Year Two BorrowedFundsMaturinginYearTwo	11690000	USD
CY2019Q4	sbsi	Borrowed Funds Maturingin Year Three BorrowedFundsMaturinginYearThree	680000	USD
CY2019Q4	sbsi	Borrowed Funds Maturingin Year Four BorrowedFundsMaturinginYearFour	710000	USD
CY2019Q4	sbsi	Borrowed Funds Maturingin Year Five BorrowedFundsMaturinginYearFive	740000	USD
CY2019Q4	sbsi	Borrowed Funds Maturing After Year Five BorrowedFundsMaturingAfterYearFive	1908000	USD
CY2019Q4	us-gaap	Debt And Capital Lease Obligations DebtAndCapitalLeaseObligations	1001102000	USD
CY2019Q4	sbsi	Line Of Credit Facility Number Of Credit Lines Maintained By Company LineOfCreditFacilityNumberOfCreditLinesMaintainedByCompany	3	credit_line
CY2019Q4	us-gaap	Federal Funds Purchased FederalFundsPurchased	0	USD
CY2018Q4	us-gaap	Federal Funds Purchased FederalFundsPurchased	28000000.0	USD
CY2019Q4	sbsi	Letters Of Credit Fhlb As Collateral LettersOfCreditFhlbAsCollateral	0	USD
CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	28400000	USD
CY2018Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	8800000	USD
CY2019	sbsi	Repurchase Agreement Counterparty Maturityof Agreements RepurchaseAgreementCounterpartyMaturityofAgreements	P1Y
CY2019Q4	us-gaap	Federal Home Loan Bank Advances General Debt Obligations Disclosures Amount Of Available Unused Funds FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresAmountOfAvailableUnusedFunds	1370000000	USD
CY2019Q4	us-gaap	Subordinated Debt SubordinatedDebt	98576000	USD
CY2018Q4	us-gaap	Subordinated Debt SubordinatedDebt	98407000	USD
CY2019Q4	us-gaap	Other Long Term Debt OtherLongTermDebt	60250000	USD
CY2018Q4	us-gaap	Other Long Term Debt OtherLongTermDebt	60246000	USD
CY2019Q4	us-gaap	Long Term Debt LongTermDebt	158826000	USD
CY2018Q4	us-gaap	Long Term Debt LongTermDebt	158653000	USD
CY2019	sbsi	Health Care Costs HealthCareCosts	7900000	USD
CY2018	sbsi	Health Care Costs HealthCareCosts	6500000	USD
CY2017	sbsi	Health Care Costs HealthCareCosts	5600000	USD
CY2019	sbsi	Other Postretirement Benefits Health Insurance Coverage For Employees Retiring Requisite Service Period OtherPostretirementBenefitsHealthInsuranceCoverageForEmployeesRetiringRequisiteServicePeriod	P50Y
CY2019Q4	sbsi	Retireesparticipatinginhealthinsurance Retireesparticipatinginhealthinsurance	1
CY2017Q4	sbsi	Retireesparticipatinginhealthinsurance Retireesparticipatinginhealthinsurance	2
CY2019	us-gaap	Employee Stock Ownership Plan Esop Cash Contributions To Esop EmployeeStockOwnershipPlanESOPCashContributionsToESOP	700000	USD
CY2017	us-gaap	Employee Stock Ownership Plan Esop Cash Contributions To Esop EmployeeStockOwnershipPlanESOPCashContributionsToESOP	350000	USD
CY2019Q4	us-gaap	Employee Stock Ownership Plan Esop Shares In Esop EmployeeStockOwnershipPlanESOPSharesInESOP	283097	shares
CY2018Q4	us-gaap	Employee Stock Ownership Plan Esop Shares In Esop EmployeeStockOwnershipPlanESOPSharesInESOP	277492	shares
CY2019	sbsi	Supplemental Unemployment Benefits Disability Related Benefits Automatic Coverage Qualification Requisite Service Period SupplementalUnemploymentBenefitsDisabilityRelatedBenefitsAutomaticCoverageQualificationRequisiteServicePeriod	P3Y
CY2019	sbsi	Supplemental Unemployment Benefits Disability Related Benefits Automatic Coverage Qualification Minimum Annual Salary Level SupplementalUnemploymentBenefitsDisabilityRelatedBenefitsAutomaticCoverageQualificationMinimumAnnualSalaryLevel	50000	USD
CY2019	sbsi	Supplemental Unemployment Benefits Disability Related Benefits Maximum Benefit Provided Per Month SupplementalUnemploymentBenefitsDisabilityRelatedBenefitsMaximumBenefitProvidedPerMonth	15000	USD
CY2019	sbsi	Defined Contribution Plan Requisite Service Period DefinedContributionPlanRequisiteServicePeriod	P30D
CY2019	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	1600000	USD
CY2018	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	1500000	USD
CY2017	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	613000	USD
CY2019	sbsi	Adjustment To Pension Liability AdjustmentToPensionLiability	-7400000	USD
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	2653000	USD
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Shares Issued In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod	122537	shares
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Shares Issued In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod	140692	shares
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Shares Issued In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod	159356	shares
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	1986000	USD
CY2017	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	2692000	USD
CY2019Q4	us-gaap	Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Number Of Outstanding Options ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions	1109559	shares
CY2019Q4	us-gaap	Sharebased Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Outstanding Options Weighted Average Exercise Price Beginning Balance1 SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1	31.55
CY2019	us-gaap	Sharebased Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Outstanding Options Weighted Average Remaining Contractual Term2 SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2	P7Y4M6D
CY2019Q4	us-gaap	Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Number Of Exercisable Options ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions	515416	shares
CY2019Q4	us-gaap	Sharebased Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Exercisable Options Weighted Average Exercise Price1 SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1	28.06
CY2019Q4	us-gaap	Debt Instrument Face Amount DebtInstrumentFaceAmount	270000000.0	USD
CY2019Q4	us-gaap	Collateral Already Posted Aggregate Fair Value CollateralAlreadyPostedAggregateFairValue	10100000	USD
CY2019Q4	us-gaap	Derivative Collateral Right To Reclaim Cash DerivativeCollateralRightToReclaimCash	883000	USD
CY2018Q4	us-gaap	Derivative Asset Collateral Obligation To Return Cash Offset DerivativeAssetCollateralObligationToReturnCashOffset	8300000	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	9600000	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	11742000	USD
CY2018Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	11594000	USD
CY2018Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	3320000	USD
CY2019Q4	us-gaap	Derivative Asset Fair Value Gross Liability DerivativeAssetFairValueGrossLiability	1569000	USD
CY2019Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	1569000	USD
CY2018Q4	us-gaap	Derivative Asset Fair Value Gross Liability DerivativeAssetFairValueGrossLiability	2201000	USD
CY2018Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	2201000	USD
CY2019Q4	us-gaap	Derivative Asset Collateral Obligation To Return Cash Offset DerivativeAssetCollateralObligationToReturnCashOffset	0	USD
CY2019Q4	us-gaap	Derivative Liability Collateral Right To Reclaim Cash Offset DerivativeLiabilityCollateralRightToReclaimCashOffset	10117000	USD
CY2018Q4	us-gaap	Derivative Asset Collateral Obligation To Return Cash Offset DerivativeAssetCollateralObligationToReturnCashOffset	8306000	USD
CY2018Q4	us-gaap	Derivative Liability Collateral Right To Reclaim Cash Offset DerivativeLiabilityCollateralRightToReclaimCashOffset	0	USD
CY2019Q4	us-gaap	Derivative Assets DerivativeAssets	8031000	USD
CY2019Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	56000	USD
CY2018Q4	us-gaap	Derivative Assets DerivativeAssets	1087000	USD
CY2018Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	1119000	USD
CY2019	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.26
CY2018	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.20
CY2017	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.11
CY2019	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	42438	shares
CY2019	sbsi	Stock Issued During Period Per Share Average Dividend Reinvestment Plan StockIssuedDuringPeriodPerShareAverageDividendReinvestmentPlan	34.04
CY2018	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	42872	shares
CY2018	sbsi	Stock Issued During Period Per Share Average Dividend Reinvestment Plan StockIssuedDuringPeriodPerShareAverageDividendReinvestmentPlan	34.45
CY2019	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	66467	shares
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	2200000	USD
CY2018	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	1459148	shares
CY2018	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	47200000	USD
CY2017	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	0	shares
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	13099000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	4009000	USD
CY2017	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	12607000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	122000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	6154000	USD
CY2017	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	3514000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	13221000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10163000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	16121000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	5207000	USD
CY2019Q4	sbsi	Deferred Tax Liabilities Pension Plan DeferredTaxLiabilitiesPensionPlan	2179000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	6842000	USD
CY2019Q4	sbsi	Deferred Tax Asset Operating Lease Liabilities DeferredTaxAssetOperatingLeaseLiabilities	2137000	USD
CY2019Q4	sbsi	Deferred Tax Liabilities Operating Lease Right Of Use Assets DeferredTaxLiabilitiesOperatingLeaseRightOfUseAssets	2049000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	1990000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Investments DeferredTaxLiabilitiesInvestments	10278000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Derivative Instruments DeferredTaxAssetsDerivativeInstruments	445000	USD
CY2019Q4	sbsi	Deferred Tax Asset Fair Value Adjustmenton Acquired Loans DeferredTaxAssetFairValueAdjustmentonAcquiredLoans	1478000	USD
CY2019Q4	sbsi	Deferred Tax Assets Unfunded Status Of Defined Benefit Plan DeferredTaxAssetsUnfundedStatusOfDefinedBenefitPlan	8540000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards General Business DeferredTaxAssetsTaxCreditCarryforwardsGeneralBusiness	423000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	914000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	629000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	19144000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	23967000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	4823000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	5673000	USD
CY2018Q4	sbsi	Deferred Tax Liabilities Pension Plan DeferredTaxLiabilitiesPensionPlan	2519000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	6360000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	2748000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Investments DeferredTaxAssetsInvestments	7926000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Derivatives DeferredTaxLiabilitiesDerivatives	1761000	USD
CY2018Q4	sbsi	Deferred Tax Asset Fair Value Adjustmenton Acquired Loans DeferredTaxAssetFairValueAdjustmentonAcquiredLoans	1894000	USD
CY2018Q4	sbsi	Deferred Tax Liability Fair Value Adjustmenton Acquired Time Deposits DeferredTaxLiabilityFairValueAdjustmentonAcquiredTimeDeposits	6000	USD
CY2018Q4	sbsi	Deferred Tax Assets Unfunded Status Of Defined Benefit Plan DeferredTaxAssetsUnfundedStatusOfDefinedBenefitPlan	6979000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards General Business DeferredTaxAssetsTaxCreditCarryforwardsGeneralBusiness	483000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	797000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	582000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	23752000	USD
CY2018Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	13976000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	9776000	USD
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	18433000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	17703000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2017	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	24652000	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.350
CY2019	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	0	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Change In Enacted Tax Rate EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate	0
CY2018	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	-767000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Change In Enacted Tax Rate EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate	-0.009
CY2017	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	2416000	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation Change In Enacted Tax Rate EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate	0.034
CY2019	sbsi	Effective Income Tax Rate Reconciliation Tax Exempt Income Other Than Life Insurance Amount EffectiveIncomeTaxRateReconciliationTaxExemptIncomeOtherThanLifeInsuranceAmount	4875000	USD
CY2019	sbsi	Effective Income Tax Rate Reconciliation Tax Exempt Income Other Than Life Insurance Percent EffectiveIncomeTaxRateReconciliationTaxExemptIncomeOtherThanLifeInsurancePercent	0.055
CY2018	sbsi	Effective Income Tax Rate Reconciliation Tax Exempt Income Other Than Life Insurance Amount EffectiveIncomeTaxRateReconciliationTaxExemptIncomeOtherThanLifeInsuranceAmount	6257000	USD
CY2018	sbsi	Effective Income Tax Rate Reconciliation Tax Exempt Income Other Than Life Insurance Percent EffectiveIncomeTaxRateReconciliationTaxExemptIncomeOtherThanLifeInsurancePercent	0.074
CY2017	sbsi	Effective Income Tax Rate Reconciliation Tax Exempt Income Other Than Life Insurance Amount EffectiveIncomeTaxRateReconciliationTaxExemptIncomeOtherThanLifeInsuranceAmount	10195000	USD
CY2017	sbsi	Effective Income Tax Rate Reconciliation Tax Exempt Income Other Than Life Insurance Percent EffectiveIncomeTaxRateReconciliationTaxExemptIncomeOtherThanLifeInsurancePercent	0.145
CY2019	sbsi	Effective Income Tax Rate Reconciliation Tax Exempt Income Life Insurance Amount EffectiveIncomeTaxRateReconciliationTaxExemptIncomeLifeInsuranceAmount	484000	USD
CY2019	sbsi	Effective Income Tax Rate Reconciliation Tax Exempt Income Life Insurance Percent EffectiveIncomeTaxRateReconciliationTaxExemptIncomeLifeInsurancePercent	0.005
CY2018	sbsi	Effective Income Tax Rate Reconciliation Tax Exempt Income Life Insurance Amount EffectiveIncomeTaxRateReconciliationTaxExemptIncomeLifeInsuranceAmount	613000	USD
CY2018	sbsi	Effective Income Tax Rate Reconciliation Tax Exempt Income Life Insurance Percent EffectiveIncomeTaxRateReconciliationTaxExemptIncomeLifeInsurancePercent	0.007
CY2017	sbsi	Effective Income Tax Rate Reconciliation Tax Exempt Income Life Insurance Amount EffectiveIncomeTaxRateReconciliationTaxExemptIncomeLifeInsuranceAmount	885000	USD
CY2017	sbsi	Effective Income Tax Rate Reconciliation Tax Exempt Income Life Insurance Percent EffectiveIncomeTaxRateReconciliationTaxExemptIncomeLifeInsurancePercent	0.012
CY2019	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	-167000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Share Based Compensation Cost EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost	-0.002
CY2018	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	-191000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Share Based Compensation Cost EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost	-0.002
CY2017	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	-482000	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Share Based Compensation Cost EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost	-0.007
CY2019	sbsi	Effective Income Tax Rate Reconciliation Transaction Costs Analysis Amount EffectiveIncomeTaxRateReconciliationTransactionCostsAnalysisAmount	0	USD
CY2019	sbsi	Effective Income Tax Rate Reconciliation Transaction Cost Analysis Percent EffectiveIncomeTaxRateReconciliationTransactionCostAnalysisPercent	0
CY2018	sbsi	Effective Income Tax Rate Reconciliation Transaction Costs Analysis Amount EffectiveIncomeTaxRateReconciliationTransactionCostsAnalysisAmount	0	USD
CY2018	sbsi	Effective Income Tax Rate Reconciliation Transaction Cost Analysis Percent EffectiveIncomeTaxRateReconciliationTransactionCostAnalysisPercent	0
CY2017	sbsi	Effective Income Tax Rate Reconciliation Transaction Costs Analysis Amount EffectiveIncomeTaxRateReconciliationTransactionCostsAnalysisAmount	467000	USD
CY2017	sbsi	Effective Income Tax Rate Reconciliation Transaction Cost Analysis Percent EffectiveIncomeTaxRateReconciliationTransactionCostAnalysisPercent	0.007
CY2019	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	217000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.002
CY2018	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	297000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.003
CY2017	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	68000	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.001
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	97000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.001
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-9000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0
CY2017	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	80000	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.001
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	13221000	USD
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.151
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10163000	USD
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.121
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	16121000	USD
CY2017	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.229
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	9755000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	10174000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	1595000	USD
CY2018	us-gaap	Operating Lease Cost OperatingLeaseCost	1764000	USD
CY2017	us-gaap	Operating Lease Cost OperatingLeaseCost	1748000	USD
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	1465000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	1205000	USD
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P12Y2M12D
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0382	Rate
CY2019Q4	us-gaap	Lessor Operating Lease Payments To Be Received LessorOperatingLeasePaymentsToBeReceived	12991000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	929000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	7197000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	13121000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	2947000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	10174000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Remainder Of Fiscal Year LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear	1331000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	1343000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	1232000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	1089000	USD
CY2019Q4	sbsi	Lessee Operating Lease Lease Not Yet Commenced Payments Due LesseeOperatingLeaseLeaseNotYetCommencedPaymentsDue	9100000	USD
CY2019	sbsi	Lessee Operating Lease Not Yet Commenced Lease Term LesseeOperatingLeaseNotYetCommencedLeaseTerm	P20Y4M24D
CY2019Q4	us-gaap	Net Rentable Area NetRentableArea	202000	sqft
CY2019Q4	sbsi	Numberof Square Feet Occupied NumberofSquareFeetOccupied	41000	sqft
CY2019	us-gaap	Operating Lease Lease Income OperatingLeaseLeaseIncome	2991000	USD
CY2018	us-gaap	Operating Lease Lease Income OperatingLeaseLeaseIncome	2987000	USD
CY2017	us-gaap	Operating Lease Lease Income OperatingLeaseLeaseIncome	3103000	USD
CY2019Q4	us-gaap	Lessor Operating Lease Payments To Be Received Remainder Of Fiscal Year LessorOperatingLeasePaymentsToBeReceivedRemainderOfFiscalYear	3131000	USD
CY2019Q4	us-gaap	Lessor Operating Lease Payments To Be Received Two Years LessorOperatingLeasePaymentsToBeReceivedTwoYears	2004000	USD
CY2019Q4	us-gaap	Lessor Operating Lease Payments To Be Received Three Years LessorOperatingLeasePaymentsToBeReceivedThreeYears	1950000	USD
CY2019Q4	us-gaap	Lessor Operating Lease Payments To Be Received Four Years LessorOperatingLeasePaymentsToBeReceivedFourYears	1680000	USD
CY2019Q4	us-gaap	Lessor Operating Lease Payments To Be Received Five Years LessorOperatingLeasePaymentsToBeReceivedFiveYears	1357000	USD
CY2019Q4	us-gaap	Lessor Operating Lease Payments To Be Received Thereafter LessorOperatingLeasePaymentsToBeReceivedThereafter	2869000	USD
CY2019Q4	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Amount Liability FairValueDisclosureOffbalanceSheetRisksAmountLiability	942882000	USD
CY2018Q4	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Amount Liability FairValueDisclosureOffbalanceSheetRisksAmountLiability	901995000	USD
CY2019Q4	sbsi	Unsettled Trades To Purchase Securities Liability UnsettledTradesToPurchaseSecuritiesLiability	17500000	USD
CY2019Q4	sbsi	Unsettled Trades To Sell Securities UnsettledTradesToSellSecurities	0	USD
CY2018Q4	sbsi	Unsettled Trades To Purchase Securities Liability UnsettledTradesToPurchaseSecuritiesLiability	6400000	USD
CY2018Q4	sbsi	Unsettled Trades To Sell Securities UnsettledTradesToSellSecurities	0	USD
CY2019Q4	sbsi	Unsettled Issuancesof Brokered C Ds UnsettledIssuancesofBrokeredCDs	20000000.0	USD
CY2018Q4	sbsi	Unsettled Issuancesof Brokered C Ds UnsettledIssuancesofBrokeredCDs	15200000	USD
CY2019Q4	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	60533000	USD
CY2019Q1	us-gaap	Noninterest Income NoninterestIncome	9282000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	42000	USD
CY2019Q3	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	42000	USD
CY2019Q3	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	60555000	USD
CY2019Q2	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	60672000	USD
CY2019Q1	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	59027000	USD
CY2019Q4	us-gaap	Interest Expense InterestExpense	17357000	USD
CY2019Q3	us-gaap	Interest Expense InterestExpense	18182000	USD
CY2019Q2	us-gaap	Interest Expense InterestExpense	17541000	USD
CY2019Q1	us-gaap	Interest Expense InterestExpense	17902000	USD
CY2019Q4	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	43176000	USD
CY2019Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	42373000	USD
CY2019Q2	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	43131000	USD
CY2019Q1	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	41125000	USD
CY2019Q4	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	2508000	USD
CY2019Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	1005000	USD
CY2019Q2	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	2506000	USD
CY2019Q1	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	-918000	USD
CY2019Q4	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	40668000	USD
CY2019Q3	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	41368000	USD
CY2019Q2	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	40625000	USD
CY2019Q1	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	42043000	USD
CY2019Q4	us-gaap	Noninterest Income NoninterestIncome	10423000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	11069000	USD
CY2019Q2	us-gaap	Noninterest Income NoninterestIncome	10838000	USD
CY2019Q2	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	416000	USD
CY2019Q1	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	256000	USD
CY2019Q4	us-gaap	Noninterest Expense NoninterestExpense	30944000	USD
CY2019Q3	us-gaap	Noninterest Expense NoninterestExpense	29026000	USD
CY2019Q2	us-gaap	Noninterest Expense NoninterestExpense	29700000	USD
CY2019Q1	us-gaap	Noninterest Expense NoninterestExpense	29627000	USD
CY2019Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	20189000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	23453000	USD
CY2019Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	22179000	USD
CY2019Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	21954000	USD
CY2019Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	2854000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3661000	USD
CY2019Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3569000	USD
CY2019Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3137000	USD
CY2019Q4	us-gaap	Net Income Loss NetIncomeLoss	17335000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	19792000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	18610000	USD
CY2019Q1	us-gaap	Net Income Loss NetIncomeLoss	18817000	USD
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.51
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.59
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.55
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.56
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.51
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.58
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.55
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.56
CY2019Q4	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.34
CY2019Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.31
CY2019Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.31
CY2019Q1	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.30
CY2019Q4	sbsi	Bookvaluepercommonshare Bookvaluepercommonshare	23.79
CY2019Q3	sbsi	Bookvaluepercommonshare Bookvaluepercommonshare	23.98
CY2019Q2	sbsi	Bookvaluepercommonshare Bookvaluepercommonshare	23.34
CY2019Q1	sbsi	Bookvaluepercommonshare Bookvaluepercommonshare	22.48
CY2018Q4	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	58022000	USD
CY2018Q3	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	57152000	USD
CY2018Q2	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	56797000	USD
CY2018Q1	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	57194000	USD
CY2018Q4	us-gaap	Interest Expense InterestExpense	15612000	USD
CY2018Q3	us-gaap	Interest Expense InterestExpense	14742000	USD
CY2018Q2	us-gaap	Interest Expense InterestExpense	13686000	USD
CY2018Q1	us-gaap	Interest Expense InterestExpense	13061000	USD
CY2018Q4	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	42410000	USD
CY2018Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	42410000	USD
CY2018Q2	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	43111000	USD
CY2018Q1	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	44133000	USD
CY2018Q4	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	2446000	USD
CY2018Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	975000	USD
CY2018Q2	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	1281000	USD
CY2018Q1	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	3735000	USD
CY2018Q4	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	39964000	USD
CY2018Q3	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	41435000	USD
CY2018Q2	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	41830000	USD
CY2018Q1	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	40398000	USD
CY2018Q4	us-gaap	Noninterest Income NoninterestIncome	10073000	USD
CY2018Q3	us-gaap	Noninterest Income NoninterestIncome	10763000	USD
CY2018Q2	us-gaap	Noninterest Income NoninterestIncome	11339000	USD
CY2018Q1	us-gaap	Noninterest Income NoninterestIncome	10437000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	61000	USD
CY2018Q3	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	-741000	USD
CY2018Q2	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	-332000	USD
CY2018Q1	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	-827000	USD
CY2018Q4	us-gaap	Noninterest Expense NoninterestExpense	30196000	USD
CY2018Q3	us-gaap	Noninterest Expense NoninterestExpense	28962000	USD
CY2018Q2	us-gaap	Noninterest Expense NoninterestExpense	29274000	USD
CY2018Q1	us-gaap	Noninterest Expense NoninterestExpense	31667000	USD
CY2018Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	19902000	USD
CY2018Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	22495000	USD
CY2018Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	23563000	USD
CY2018Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	18341000	USD
CY2018Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	2521000	USD
CY2018Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	2192000	USD
CY2018Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3360000	USD
CY2018Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	2090000	USD
CY2018Q4	us-gaap	Net Income Loss NetIncomeLoss	17381000	USD
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	20303000	USD
CY2018Q2	us-gaap	Net Income Loss NetIncomeLoss	20203000	USD
CY2018Q1	us-gaap	Net Income Loss NetIncomeLoss	16251000	USD
CY2018Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.50
CY2018Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.58
CY2018Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.58
CY2018Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.46
CY2018Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.50
CY2018Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.58
CY2018Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.57
CY2018Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.46
CY2018Q4	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.32
CY2018Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.30
CY2018Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.30
CY2018Q1	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.28
CY2018Q4	sbsi	Bookvaluepercommonshare Bookvaluepercommonshare	21.68
CY2018Q3	sbsi	Bookvaluepercommonshare Bookvaluepercommonshare	21.40
CY2018Q2	sbsi	Bookvaluepercommonshare Bookvaluepercommonshare	21.43
CY2018Q1	sbsi	Bookvaluepercommonshare Bookvaluepercommonshare	21.29

Files In Submission

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$SBSI
SOUTHSIDE BANCSHARES INC Stock $sbsi

2018 Q4 Form 10-K Financial Statement

#000070543220000022 Filed on February 28, 2020

Income Statement

Balance Sheet

Cashflow Statement

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$SBSI SOUTHSIDE BANCSHARES INC Stock $sbsi

2018 Q4 Form 10-K Financial Statement

#000070543220000022 Filed on February 28, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SBSI
SOUTHSIDE BANCSHARES INC Stock $sbsi