$SBSI
SOUTHSIDE BANCSHARES INC Stock $sbsi

$sbsi Overview Financials Valuation SEC Filings Company Website

2019 Q4 Form 10-Q Financial Statement

#000070543219000128 Filed on October 31, 2019

Income Statement

Concept	2019 Q4	2019 Q3	2018 Q3
Revenue	$60.53M	$60.56M	$57.15M
YoY Change	4.33%	5.95%	22.98%
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	$3.000M	$3.000M	$3.500M
YoY Change	-11.76%	-14.29%	40.0%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense	$17.36M	$18.18M	$14.74M
YoY Change	11.18%	23.33%	28.05%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$20.19M	$23.45M	$22.50M
YoY Change	1.44%	4.26%	22.25%
Income Tax	$2.854M	$3.661M	$2.192M
% Of Pretax Income	14.14%	15.61%	9.74%
Net Earnings	$17.34M	$19.79M	$20.30M
YoY Change	-0.26%	-2.52%	39.91%
Net Earnings / Revenue	28.64%	32.68%	35.52%
Basic Earnings Per Share	$0.51	$0.59	$0.58
Diluted Earnings Per Share	$0.51	$0.58	$0.58
COMMON SHARES
Basic Shares Outstanding	33.77M shares	33.77M shares	35.11M shares
Diluted Shares Outstanding		33.90M shares	35.29M shares

Balance Sheet

Concept	2019 Q4	2019 Q3	2018 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$110.7M	$114.8M	$174.1M
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	$143.9M	$141.7M	$133.9M
YoY Change	5.84%	5.78%	25.06%
Goodwill	$201.1M	$201.1M	$201.1M
YoY Change	0.0%	-0.01%	119.75%
Intangibles	$13.36M	$14.39M	$19.01M
YoY Change	-24.85%	-24.29%	462.56%
Long-Term Investments	$12.30M	$12.40M
YoY Change	1.65%
Other Assets	$0.00	$0.00	$16.40M
YoY Change	-100.0%	-100.0%	-24.77%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$6.749B	$6.542B	$6.105B
YoY Change	10.21%	7.15%	11.32%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$10.20M	$10.50M
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt	$28.40M	$9.600M	$9.000M
YoY Change	-22.83%	6.67%	-99.1%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$10.20M	$10.50M	$9.000M
YoY Change	-72.28%	16.67%	-1.1%
LONG-TERM LIABILITIES
Long-Term Debt	$158.8M	$158.8M	$158.6M
YoY Change	0.06%	0.13%	0.13%
Other Long-Term Liabilities	$66.60M	$75.00M	$70.50M
YoY Change	26.62%	6.38%	30.31%
Total Long-Term Liabilities	$225.4M	$233.8M	$229.1M
YoY Change	6.67%	2.05%	7.81%
TOTAL LIABILITIES
Total Short-Term Liabilities	$10.20M	$10.50M	$9.000M
Total Long-Term Liabilities	$225.4M	$233.8M	$229.1M
Total Liabilities	$5.944B	$5.732B	$5.353B
YoY Change	10.24%	7.08%	8.61%
SHAREHOLDERS EQUITY
Retained Earnings	$80.27M	$74.48M	$58.58M
YoY Change	23.89%	27.14%	128.13%
Common Stock	$814.1M	$812.9M	$808.9M
YoY Change	0.53%	0.49%	33.95%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$94.01M	$93.57M	$45.97M
YoY Change	1.02%	103.57%	-2.8%
Treasury Stock Shares	4.064M shares	4.083M shares	2.673M shares
Shareholders Equity	$804.6M	$810.5M	$752.5M
YoY Change
Total Liabilities & Shareholders Equity	$6.749B	$6.542B	$6.105B
YoY Change	10.21%	7.15%	11.32%

Cashflow Statement

Concept	2019 Q4	2019 Q3	2018 Q3
OPERATING ACTIVITIES
Net Income	$17.34M	$19.79M	$20.30M
YoY Change	-0.26%	-2.52%	39.91%
Depreciation, Depletion And Amortization	$3.000M	$3.000M	$3.500M
YoY Change	-11.76%	-14.29%	40.0%
Cash From Operating Activities	$20.60M	$25.20M	$32.60M
YoY Change	6.74%	-22.7%	13.59%
INVESTING ACTIVITIES
Capital Expenditures	-$4.500M	-$3.500M	-$3.700M
YoY Change	0.0%	-5.41%	15.63%
Acquisitions
YoY Change
Other Investing Activities	-$213.4M	-$180.1M	$101.6M
YoY Change	244.75%	-277.26%	318.11%
Cash From Investing Activities	-$217.8M	-$183.7M	$97.80M
YoY Change	228.01%	-287.83%	361.32%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	193.1M	140.8M	-188.4M
YoY Change	-3165.08%	-174.73%	86.35%
NET CHANGE
Cash From Operating Activities	20.60M	25.20M	32.60M
Cash From Investing Activities	-217.8M	-183.7M	97.80M
Cash From Financing Activities	193.1M	140.8M	-188.4M
Net Change In Cash	-4.100M	-17.70M	-58.00M
YoY Change	-92.32%	-69.48%	13.28%
FREE CASH FLOW
Cash From Operating Activities	$20.60M	$25.20M	$32.60M
Capital Expenditures	-$4.500M	-$3.500M	-$3.700M
Free Cash Flow	$25.10M	$28.70M	$36.30M
YoY Change	5.46%	-20.94%	13.79%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2019Q3	sbsi	Atm Expense ATMExpense	232000	USD
	dei	Amendment Flag AmendmentFlag	false
	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	Q3
	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2019
	dei	Entity Central Index Key EntityCentralIndexKey	0000705432
CY2018	sbsi	Securities Transferred From Available For Sale To Held To Maturity SecuritiesTransferredFromAvailableForSaleToHeldToMaturity	0	USD
CY2018Q1	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.28
CY2018Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.30
CY2018Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.30
CY2019Q1	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.30
CY2019Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.31
CY2018Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	1.25
CY2019Q3	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	1.25
CY2018Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	80000000	shares
CY2019Q3	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	80000000	shares
CY2018Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	37845224	shares
CY2019Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	37877103	shares
CY2018Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2018Q4	us-gaap	Goodwill Goodwill	201100000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	0	USD
CY2018Q3	us-gaap	Loans And Leases Receivable Impaired Commitment To Lend LoansAndLeasesReceivableImpairedCommitmentToLend	0	USD
	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	0	USD
	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	0	USD
CY2018Q1	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	10035	shares
CY2018Q2	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	10397	shares
CY2018Q3	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	10205	shares
CY2019Q1	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	10565	shares
CY2019Q2	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	10570	shares
CY2019Q3	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	10744	shares
CY2018Q1	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	42179	shares
CY2018Q2	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	20872	shares
CY2018Q3	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	65918	shares
CY2019Q1	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	23617	shares
CY2019Q2	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	20115	shares
CY2019Q3	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	35070	shares
CY2018Q3	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Deferred Tax Asset Income Tax Expense TaxCutsAndJobsActOf2017ChangeInTaxRateDeferredTaxAssetIncomeTaxExpense	-800000	USD
CY2018Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	4120475	shares
CY2019Q3	us-gaap	Treasury Stock Shares TreasuryStockShares	4082525	shares
CY2019Q1	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	40852	shares
	dei	Document Type DocumentType	10-Q
	dei	Document Quarterly Report DocumentQuarterlyReport	true
	dei	Document Period End Date DocumentPeriodEndDate	2019-09-30
	dei	Document Transition Report DocumentTransitionReport	false
	dei	Entity File Number EntityFileNumber	000-12247
	dei	Entity Registrant Name EntityRegistrantName	SOUTHSIDE BANCSHARES INC
	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	TX
	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	75-1848732
	dei	Entity Address Address Line1 EntityAddressAddressLine1	1201 S. Beckham Avenue,
	dei	Entity Address City Or Town EntityAddressCityOrTown	Tyler,
	dei	Entity Address State Or Province EntityAddressStateOrProvince	TX
	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	75701
	dei	City Area Code CityAreaCode	903
	dei	Local Phone Number LocalPhoneNumber	531-7111
	dei	Security12b Title Security12bTitle	Common Stock, $1.25 par value
	dei	Trading Symbol TradingSymbol	SBSI
	dei	Security Exchange Name SecurityExchangeName	NASDAQ
	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
	dei	Entity Small Business EntitySmallBusiness	false
	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
	dei	Entity Shell Company EntityShellCompany	false
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CY2019Q3	us-gaap	Interest Receivable InterestReceivable	22483000	USD
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	us-gaap	Interest Expense Deposits InterestExpenseDeposits	34064000	USD
	us-gaap	Interest Expense Deposits InterestExpenseDeposits	25529000	USD
CY2019Q3	sbsi	Interestexpense Federal Home Loan Bank Advances InterestexpenseFederalHomeLoanBankAdvances	4647000	USD
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	sbsi	Interestexpense Federal Home Loan Bank Advances InterestexpenseFederalHomeLoanBankAdvances	13003000	USD
	sbsi	Interestexpense Federal Home Loan Bank Advances InterestexpenseFederalHomeLoanBankAdvances	9747000	USD
CY2019Q3	us-gaap	Interest Expense Subordinated Notes And Debentures InterestExpenseSubordinatedNotesAndDebentures	1425000	USD
CY2018Q3	us-gaap	Interest Expense Subordinated Notes And Debentures InterestExpenseSubordinatedNotesAndDebentures	1423000	USD
	us-gaap	Interest Expense Subordinated Notes And Debentures InterestExpenseSubordinatedNotesAndDebentures	4235000	USD
	us-gaap	Interest Expense Subordinated Notes And Debentures InterestExpenseSubordinatedNotesAndDebentures	4228000	USD
CY2019Q3	us-gaap	Interest Expense Junior Subordinated Debentures InterestExpenseJuniorSubordinatedDebentures	685000	USD
CY2018Q3	us-gaap	Interest Expense Junior Subordinated Debentures InterestExpenseJuniorSubordinatedDebentures	684000	USD
	us-gaap	Interest Expense Junior Subordinated Debentures InterestExpenseJuniorSubordinatedDebentures	2132000	USD
	us-gaap	Interest Expense Junior Subordinated Debentures InterestExpenseJuniorSubordinatedDebentures	1911000	USD
CY2019Q3	us-gaap	Interest Expense Other InterestExpenseOther	59000	USD
CY2018Q3	us-gaap	Interest Expense Other InterestExpenseOther	30000	USD
	us-gaap	Interest Expense Other InterestExpenseOther	191000	USD
	us-gaap	Interest Expense Other InterestExpenseOther	74000	USD
CY2019Q3	us-gaap	Interest Expense InterestExpense	18182000	USD
CY2018Q3	us-gaap	Interest Expense InterestExpense	14742000	USD
	us-gaap	Interest Expense InterestExpense	53625000	USD
	us-gaap	Interest Expense InterestExpense	41489000	USD
CY2019Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	42373000	USD
CY2018Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	42410000	USD
	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	126629000	USD
	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	129654000	USD
CY2019Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	1005000	USD
CY2018Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	975000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	2593000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	5991000	USD
CY2019Q3	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	41368000	USD
CY2018Q3	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	41435000	USD
	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	124036000	USD
	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	123663000	USD
CY2019Q3	sbsi	Fee And Commissions Depositor Account FeeAndCommissionsDepositorAccount	6753000	USD
CY2018Q3	sbsi	Fee And Commissions Depositor Account FeeAndCommissionsDepositorAccount	6317000	USD
	sbsi	Fee And Commissions Depositor Account FeeAndCommissionsDepositorAccount	19391000	USD
	sbsi	Fee And Commissions Depositor Account FeeAndCommissionsDepositorAccount	18757000	USD
CY2019Q3	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	42000	USD
CY2018Q3	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-741000	USD
CY2018Q3	us-gaap	Noninterest Income NoninterestIncome	10022000	USD
	us-gaap	Noninterest Income NoninterestIncome	31903000	USD
	us-gaap	Noninterest Income NoninterestIncome	30639000	USD
CY2019Q3	us-gaap	Labor And Related Expense LaborAndRelatedExpense	18388000	USD
	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	714000	USD
	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-1900000	USD
CY2019Q3	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	131000	USD
CY2018Q3	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	303000	USD
	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	405000	USD
	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	591000	USD
CY2019Q3	sbsi	Fees And Commissions Fiduciary And Trust Activity FeesAndCommissionsFiduciaryAndTrustActivity	1523000	USD
CY2018Q3	sbsi	Fees And Commissions Fiduciary And Trust Activity FeesAndCommissionsFiduciaryAndTrustActivity	1568000	USD
	sbsi	Fees And Commissions Fiduciary And Trust Activity FeesAndCommissionsFiduciaryAndTrustActivity	4584000	USD
	sbsi	Fees And Commissions Fiduciary And Trust Activity FeesAndCommissionsFiduciaryAndTrustActivity	5259000	USD
CY2019Q3	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	622000	USD
CY2018Q3	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	552000	USD
	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1725000	USD
	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2369000	USD
CY2019Q3	us-gaap	Brokerage Commissions Revenue BrokerageCommissionsRevenue	555000	USD
CY2018Q3	us-gaap	Brokerage Commissions Revenue BrokerageCommissionsRevenue	532000	USD
	us-gaap	Brokerage Commissions Revenue BrokerageCommissionsRevenue	1549000	USD
	us-gaap	Brokerage Commissions Revenue BrokerageCommissionsRevenue	1488000	USD
CY2019Q3	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	1485000	USD
CY2018Q3	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	1491000	USD
	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	3535000	USD
	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	4075000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	11111000	USD
CY2018Q3	us-gaap	Labor And Related Expense LaborAndRelatedExpense	17628000	USD
	us-gaap	Labor And Related Expense LaborAndRelatedExpense	54325000	USD
	us-gaap	Labor And Related Expense LaborAndRelatedExpense	52820000	USD
CY2019Q3	us-gaap	Occupancy Net OccupancyNet	3430000	USD
CY2018Q3	us-gaap	Occupancy Net OccupancyNet	3396000	USD
	us-gaap	Occupancy Net OccupancyNet	9894000	USD
	us-gaap	Occupancy Net OccupancyNet	10339000	USD
CY2019Q3	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	0	USD
CY2018Q3	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	437000	USD
	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	0	USD
	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	2295000	USD
CY2019Q3	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	593000	USD
CY2018Q3	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	648000	USD
	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	2173000	USD
	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	2108000	USD
CY2018Q3	sbsi	Atm Expense ATMExpense	251000	USD
	sbsi	Atm Expense ATMExpense	658000	USD
	sbsi	Atm Expense ATMExpense	840000	USD
CY2019Q3	us-gaap	Professional Fees ProfessionalFees	1192000	USD
CY2018Q3	us-gaap	Professional Fees ProfessionalFees	824000	USD
	us-gaap	Professional Fees ProfessionalFees	3575000	USD
	us-gaap	Professional Fees ProfessionalFees	2846000	USD
CY2019Q3	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	1116000	USD
CY2018Q3	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	977000	USD
	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	3278000	USD
	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	2939000	USD
CY2019Q3	us-gaap	Communication Communication	480000	USD
CY2018Q3	us-gaap	Communication Communication	354000	USD
	us-gaap	Communication Communication	1456000	USD
	us-gaap	Communication Communication	1370000	USD
CY2019Q3	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	0	USD
CY2018Q3	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	435000	USD
	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	859000	USD
	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	1416000	USD
CY2019Q3	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1080000	USD
CY2018Q3	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1279000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	3388000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	3985000	USD
CY2019Q3	us-gaap	Other Noninterest Expense OtherNoninterestExpense	2515000	USD
CY2018Q3	us-gaap	Other Noninterest Expense OtherNoninterestExpense	2733000	USD
	us-gaap	Other Noninterest Expense OtherNoninterestExpense	8747000	USD
	us-gaap	Other Noninterest Expense OtherNoninterestExpense	8945000	USD
CY2019Q3	us-gaap	Noninterest Expense NoninterestExpense	29026000	USD
CY2018Q3	us-gaap	Noninterest Expense NoninterestExpense	28962000	USD
	us-gaap	Noninterest Expense NoninterestExpense	88353000	USD
	us-gaap	Noninterest Expense NoninterestExpense	89903000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	23453000	USD
CY2018Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	22495000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	67586000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	64399000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3661000	USD
CY2018Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	2192000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10367000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	7642000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	19792000	USD
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	20303000	USD
	us-gaap	Net Income Loss NetIncomeLoss	57219000	USD
	us-gaap	Net Income Loss NetIncomeLoss	56757000	USD
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.59
CY2018Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.58
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.70
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.62
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.58
CY2018Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.58
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.69
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.61
CY2019Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.31
CY2018Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.30
	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.92
	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.88
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	19792000	USD
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	20303000	USD
	us-gaap	Net Income Loss NetIncomeLoss	57219000	USD
	us-gaap	Net Income Loss NetIncomeLoss	56757000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	17334000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-16885000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	96156000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-65039000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Reclassification Adjustment For Held To Maturity Transferred To Available For Sale Securities Before Tax OtherComprehensiveIncomeReclassificationAdjustmentForHeldToMaturityTransferredToAvailableForSaleSecuritiesBeforeTax	0	USD
CY2018Q3	us-gaap	Other Comprehensive Income Reclassification Adjustment For Held To Maturity Transferred To Available For Sale Securities Before Tax OtherComprehensiveIncomeReclassificationAdjustmentForHeldToMaturityTransferredToAvailableForSaleSecuritiesBeforeTax	0	USD
	us-gaap	Other Comprehensive Income Reclassification Adjustment For Held To Maturity Transferred To Available For Sale Securities Before Tax OtherComprehensiveIncomeReclassificationAdjustmentForHeldToMaturityTransferredToAvailableForSaleSecuritiesBeforeTax	0	USD
	us-gaap	Other Comprehensive Income Reclassification Adjustment For Held To Maturity Transferred To Available For Sale Securities Before Tax OtherComprehensiveIncomeReclassificationAdjustmentForHeldToMaturityTransferredToAvailableForSaleSecuritiesBeforeTax	11881000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Transfers From Held To Maturity To Available For Sale Securities Net Of Tax OtherComprehensiveIncomeLossTransfersFromHeldToMaturityToAvailableForSaleSecuritiesNetOfTax	0	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Transfers From Held To Maturity To Available For Sale Securities Net Of Tax OtherComprehensiveIncomeLossTransfersFromHeldToMaturityToAvailableForSaleSecuritiesNetOfTax	0	USD
	us-gaap	Other Comprehensive Income Loss Transfers From Held To Maturity To Available For Sale Securities Net Of Tax OtherComprehensiveIncomeLossTransfersFromHeldToMaturityToAvailableForSaleSecuritiesNetOfTax	0	USD
	us-gaap	Other Comprehensive Income Loss Transfers From Held To Maturity To Available For Sale Securities Net Of Tax OtherComprehensiveIncomeLossTransfersFromHeldToMaturityToAvailableForSaleSecuritiesNetOfTax	401000	USD
CY2019Q3	sbsi	Amortizationof Unrealized Gains Losseson Securities Transferred Between Availablefor Sale And Heldto Maturity Debt Securities Before Tax AmortizationofUnrealizedGainsLossesonSecuritiesTransferredBetweenAvailableforSaleAndHeldtoMaturityDebtSecuritiesBeforeTax	-112000	USD
CY2018Q3	sbsi	Amortizationof Unrealized Gains Losseson Securities Transferred Between Availablefor Sale And Heldto Maturity Debt Securities Before Tax AmortizationofUnrealizedGainsLossesonSecuritiesTransferredBetweenAvailableforSaleAndHeldtoMaturityDebtSecuritiesBeforeTax	661000	USD
	sbsi	Amortizationof Unrealized Gains Losseson Securities Transferred Between Availablefor Sale And Heldto Maturity Debt Securities Before Tax AmortizationofUnrealizedGainsLossesonSecuritiesTransferredBetweenAvailableforSaleAndHeldtoMaturityDebtSecuritiesBeforeTax	-683000	USD
	sbsi	Amortizationof Unrealized Gains Losseson Securities Transferred Between Availablefor Sale And Heldto Maturity Debt Securities Before Tax AmortizationofUnrealizedGainsLossesonSecuritiesTransferredBetweenAvailableforSaleAndHeldtoMaturityDebtSecuritiesBeforeTax	-729000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	42000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-741000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	714000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-1900000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	-2619000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	1894000	USD
	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	-11392000	USD
	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax	7864000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	499000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	406000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	1809000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax	864000	USD
CY2019Q3	sbsi	Other Comprehensive Income Loss Defined Benefit Plan Gain Lossand Prior Service Cost Credit Reclassification Adjustmentfrom Aoc Ibefore Tax OtherComprehensiveIncomeLossDefinedBenefitPlanGainLossandPriorServiceCostCreditReclassificationAdjustmentfromAOCIbeforeTax	595000	USD
CY2018Q3	sbsi	Other Comprehensive Income Loss Defined Benefit Plan Gain Lossand Prior Service Cost Credit Reclassification Adjustmentfrom Aoc Ibefore Tax OtherComprehensiveIncomeLossDefinedBenefitPlanGainLossandPriorServiceCostCreditReclassificationAdjustmentfromAOCIbeforeTax	546000	USD
	sbsi	Other Comprehensive Income Loss Defined Benefit Plan Gain Lossand Prior Service Cost Credit Reclassification Adjustmentfrom Aoc Ibefore Tax OtherComprehensiveIncomeLossDefinedBenefitPlanGainLossandPriorServiceCostCreditReclassificationAdjustmentfromAOCIbeforeTax	1784000	USD
	sbsi	Other Comprehensive Income Loss Defined Benefit Plan Gain Lossand Prior Service Cost Credit Reclassification Adjustmentfrom Aoc Ibefore Tax OtherComprehensiveIncomeLossDefinedBenefitPlanGainLossandPriorServiceCostCreditReclassificationAdjustmentfromAOCIbeforeTax	1637000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	14881000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-14771000	USD
	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	84708000	USD
	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-41491000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	3125000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-3102000	USD
	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	17789000	USD
	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-8713000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	11756000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-11669000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	66919000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-32778000	USD
CY2019Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	31548000	USD
CY2018Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	8634000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	124138000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	23979000	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	754140000	USD
CY2018Q1	us-gaap	Cumulative Effect Of New Accounting Principle In Period Of Adoption CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	0	USD
CY2018Q1	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest Adjusted Balance1 StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1	754140000	USD
CY2018Q1	us-gaap	Net Income Loss NetIncomeLoss	16251000	USD
CY2018Q1	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-15757000	USD
CY2018Q1	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	353000	USD
CY2018Q1	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	456000	USD
CY2018Q1	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	761000	USD
CY2018Q1	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	9808000	USD
CY2018Q1	us-gaap	Stockholders Equity StockholdersEquity	746396000	USD
CY2018Q2	us-gaap	Net Income Loss NetIncomeLoss	20203000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-5352000	USD
CY2018Q2	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	367000	USD
CY2018Q2	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	509000	USD
CY2018Q2	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	204000	USD
CY2018Q2	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	10517000	USD
CY2018Q2	us-gaap	Stockholders Equity StockholdersEquity	751810000	USD
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	20303000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-11669000	USD
CY2018Q3	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	369000	USD
CY2018Q3	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	661000	USD
CY2018Q3	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	1565000	USD
CY2018Q3	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	10533000	USD
CY2018Q3	us-gaap	Stockholders Equity StockholdersEquity	752506000	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
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	731291000	USD
CY2019Q3	us-gaap	Stockholders Equity StockholdersEquity	810453000	USD
	us-gaap	Profit Loss ProfitLoss	57219000	USD
CY2019Q1	us-gaap	Net Income Loss NetIncomeLoss	18817000	USD
CY2019Q1	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	34455000	USD
CY2019Q1	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	355000	USD
CY2019Q1	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	1325000	USD
CY2019Q1	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	661000	USD
CY2019Q1	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	338000	USD
CY2019Q1	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	10107000	USD
CY2019Q1	us-gaap	Stockholders Equity StockholdersEquity	758033000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	18610000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	20708000	USD
CY2019Q2	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	349000	USD
CY2019Q2	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	571000	USD
CY2019Q2	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	-53000	USD
CY2019Q2	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	10453000	USD
CY2019Q2	us-gaap	Stockholders Equity StockholdersEquity	787765000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	19792000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	11756000	USD
CY2019Q3	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	353000	USD
CY2019Q3	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	522000	USD
CY2019Q3	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	736000	USD
CY2019Q3	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	10471000	USD
	us-gaap	Profit Loss ProfitLoss	56757000	USD
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	9110000	USD
	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	10571000	USD
	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-9370000	USD
	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-10875000	USD
	us-gaap	Investment Income Net Amortization Of Discount And Premium InvestmentIncomeNetAmortizationOfDiscountAndPremium	1056000	USD
	us-gaap	Investment Income Net Amortization Of Discount And Premium InvestmentIncomeNetAmortizationOfDiscountAndPremium	2021000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	2593000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	5991000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	1754000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	1626000	USD
	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-4000	USD
	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	4535000	USD
	us-gaap	Availableforsale Securities Gross Realized Gain Loss Excluding Other Than Temporary Impairments AvailableforsaleSecuritiesGrossRealizedGainLossExcludingOtherThanTemporaryImpairments	714000	USD
	us-gaap	Availableforsale Securities Gross Realized Gain Loss Excluding Other Than Temporary Impairments AvailableforsaleSecuritiesGrossRealizedGainLossExcludingOtherThanTemporaryImpairments	-1900000	USD
	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	-258000	USD
	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	-379000	USD
	us-gaap	Proceeds From Sale Of Mortgage Loans Held For Sale ProceedsFromSaleOfMortgageLoansHeldForSale	16862000	USD
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	7639000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	59954000	USD
	us-gaap	Proceeds From Sale Of Mortgage Loans Held For Sale ProceedsFromSaleOfMortgageLoansHeldForSale	19612000	USD
	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	17261000	USD
	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	18565000	USD
	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	93000	USD
	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	-411000	USD
	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	0	USD
	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	124000	USD
	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	-4804000	USD
	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	-6035000	USD
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	15280000	USD
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	1672000	USD
	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	16000	USD
	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	-839000	USD
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-7624000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	103110000	USD
	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	999403000	USD
	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	228281000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	728107000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	394232000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	114739000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	122135000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	21809000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	2656000	USD
	us-gaap	Proceeds From Sale Of Federal Reserve Stock ProceedsFromSaleOfFederalReserveStock	8788000	USD
	us-gaap	Proceeds From Sale Of Federal Reserve Stock ProceedsFromSaleOfFederalReserveStock	24360000	USD
	us-gaap	Payments To Acquire Federal Reserve Stock PaymentsToAcquireFederalReserveStock	21504000	USD
	us-gaap	Payments To Acquire Federal Reserve Stock PaymentsToAcquireFederalReserveStock	1174000	USD
	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	191116000	USD
	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	-15892000	USD
	us-gaap	Proceeds From Sale Of Loans Receivable ProceedsFromSaleOfLoansReceivable	0	USD
	us-gaap	Proceeds From Sale Of Loans Receivable ProceedsFromSaleOfLoansReceivable	4300000	USD
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	11449000	USD
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	8863000	USD
	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	94000	USD
	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	1905000	USD
	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	674000	USD
	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	771000	USD
	us-gaap	Proceeds From Sale Of Foreclosed Assets ProceedsFromSaleOfForeclosedAssets	275000	USD
	us-gaap	Proceeds From Sale Of Foreclosed Assets ProceedsFromSaleOfForeclosedAssets	378000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-348986000	USD
	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	263000	USD
	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	125000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	328311000	USD
	us-gaap	Net Change Interest And Noninterest Bearing Deposits Domestic NetChangeInterestAndNoninterestBearingDepositsDomestic	80711000	USD
	us-gaap	Net Change Interest And Noninterest Bearing Deposits Domestic NetChangeInterestAndNoninterestBearingDepositsDomestic	27809000	USD
	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	-27184000	USD
	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	-523000	USD
	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	4368700000	USD
	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	2569000000	USD
	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	4108812000	USD
	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	3025088000	USD
	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	1284000	USD
	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	2655000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	1325000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	USD
	us-gaap	Proceeds From Issuance Of Common Stock Dividend Reinvestment Plan ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	1057000	USD
	us-gaap	Proceeds From Issuance Of Common Stock Dividend Reinvestment Plan ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	1089000	USD
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	31031000	USD
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	30858000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	283137000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-456041000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-5895000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-24620000	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
CY2019Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	114824000	USD
CY2018Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	174072000	USD
	us-gaap	Interest Paid Net InterestPaidNet	53610000	USD
	us-gaap	Interest Paid Net InterestPaidNet	42209000	USD
	us-gaap	Income Taxes Paid IncomeTaxesPaid	7500000	USD
	us-gaap	Income Taxes Paid IncomeTaxesPaid	2000000	USD
	sbsi	Loans Transferred To Other Repossessed Assets And Real Estate Through Foreclosure LoansTransferredToOtherRepossessedAssetsAndRealEstateThroughForeclosure	606000	USD
	sbsi	Loans Transferred To Other Repossessed Assets And Real Estate Through Foreclosure LoansTransferredToOtherRepossessedAssetsAndRealEstateThroughForeclosure	1220000	USD
	us-gaap	Transfer Of Portfolio Loans And Leases To Held For Sale1 TransferOfPortfolioLoansAndLeasesToHeldForSale1	0	USD
	us-gaap	Transfer Of Portfolio Loans And Leases To Held For Sale1 TransferOfPortfolioLoansAndLeasesToHeldForSale1	3984000	USD
	us-gaap	Debt Securities Held To Maturity Transfer Amount DebtSecuritiesHeldToMaturityTransferAmount	0	USD
	us-gaap	Debt Securities Held To Maturity Transfer Amount DebtSecuritiesHeldToMaturityTransferAmount	743421000	USD
	sbsi	Adjustment To Pension Liability AdjustmentToPensionLiability	1784000	USD
	sbsi	Adjustment To Pension Liability AdjustmentToPensionLiability	1637000	USD
CY2019Q3	sbsi	Unsettled Trades To Purchase Securities Liability UnsettledTradesToPurchaseSecuritiesLiability	30270000	USD
CY2018Q3	sbsi	Unsettled Trades To Purchase Securities Liability UnsettledTradesToPurchaseSecuritiesLiability	28662000	USD
CY2019Q3	sbsi	Unsettled Trades To Sell Securities UnsettledTradesToSellSecurities	0	USD
CY2018Q3	sbsi	Unsettled Trades To Sell Securities UnsettledTradesToSellSecurities	14602000	USD
CY2019Q3	sbsi	Unsettled Issuancesof Brokered C Ds UnsettledIssuancesofBrokeredCDs	0	USD
CY2018Q3	sbsi	Unsettled Issuancesof Brokered C Ds UnsettledIssuancesofBrokeredCDs	10000000	USD
CY2019Q3	us-gaap	Business Acquisition Purchase Price Allocation Goodwill Expected Tax Deductible Amount BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount	0	USD
CY2019Q3	us-gaap	Goodwill Goodwill	201100000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	19792000	USD
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	20303000	USD
	us-gaap	Net Income Loss NetIncomeLoss	57219000	USD
	us-gaap	Net Income Loss NetIncomeLoss	56757000	USD
CY2019Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	33773000	shares
CY2018Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	35114000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	33732000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	35066000	shares
CY2019Q3	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	128000	shares
CY2018Q3	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	174000	shares
	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	146000	shares
	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	175000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	33901000	shares
CY2018Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	35288000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	33878000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	35241000	shares
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.59
CY2018Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.58
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.70
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.62
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.58
CY2018Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.58
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.69
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.61
CY2019Q3	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	477000	shares
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	482000	shares
CY2018Q3	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	497000	shares
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	310000	shares
CY2019Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-132000	USD
CY2018Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-174000	USD
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	44000	USD
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-2689000	USD
CY2019Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	2179809000	USD
CY2019Q3	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	61982000	USD
CY2019Q3	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	1410000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	2240381000	USD
CY2019Q3	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	140955000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	6206000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	121000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	147040000	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
CY2019Q3	sbsi	Transferred Securities Unrealized Loss Before Tax TransferredSecuritiesUnrealizedLossBeforeTax	3800000	USD
CY2019Q3	sbsi	Securitiestransferred Unrealized Loss Netof Tax SecuritiestransferredUnrealizedLossNetofTax	3000000.0	USD
CY2018Q4	sbsi	Transferred Securities Unrealized Loss Before Tax TransferredSecuritiesUnrealizedLossBeforeTax	15300000	USD
CY2018Q4	sbsi	Securitiestransferred Unrealized Loss Netof Tax SecuritiestransferredUnrealizedLossNetofTax	12100000	USD
	sbsi	Securities Transferred From Available For Sale To Held To Maturity SecuritiesTransferredFromAvailableForSaleToHeldToMaturity	0	USD
CY2019Q3	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	125605000	USD
CY2019Q3	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	1088000	USD
CY2019Q3	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	36895000	USD
CY2019Q3	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	322000	USD
CY2019Q3	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	162500000	USD
CY2019Q3	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	1410000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	287000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	3000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	4157000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	118000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue	4444000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	121000	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
CY2019Q3	sbsi	Af Ssecuritiesand Ht Msecuritieswithotherthantemporaryimpairment AFSsecuritiesandHTMsecuritieswithotherthantemporaryimpairment	0
CY2019Q3	us-gaap	Interest And Other Income InterestAndOtherIncome	16762000	USD
CY2018Q3	us-gaap	Interest And Other Income InterestAndOtherIncome	16453000	USD
CY2019Q3	us-gaap	Interest Income Securities Us Treasury InterestIncomeSecuritiesUSTreasury	0	USD
CY2018Q3	us-gaap	Interest Income Securities Us Treasury InterestIncomeSecuritiesUSTreasury	10000	USD
CY2019Q3	us-gaap	Interest Income Securities State And Municipal InterestIncomeSecuritiesStateAndMunicipal	4167000	USD
CY2018Q3	us-gaap	Interest Income Securities State And Municipal InterestIncomeSecuritiesStateAndMunicipal	6331000	USD
CY2019Q3	sbsi	Interest Income Other Stocks And Bonds InterestIncomeOtherStocksAndBonds	26000	USD
CY2018Q3	sbsi	Interest Income Other Stocks And Bonds InterestIncomeOtherStocksAndBonds	26000	USD
CY2019Q3	us-gaap	Interest Income Securities Mortgage Backed InterestIncomeSecuritiesMortgageBacked	12569000	USD
CY2018Q3	us-gaap	Interest Income Securities Mortgage Backed InterestIncomeSecuritiesMortgageBacked	10086000	USD
	us-gaap	Interest Income Securities Us Treasury InterestIncomeSecuritiesUSTreasury	0	USD
	us-gaap	Interest Income Securities Us Treasury InterestIncomeSecuritiesUSTreasury	141000	USD
	us-gaap	Interest Income Securities Other Us Government InterestIncomeSecuritiesOtherUSGovernment	0	USD
	us-gaap	Interest Income Securities Other Us Government InterestIncomeSecuritiesOtherUSGovernment	89000	USD
	us-gaap	Interest Income Securities State And Municipal InterestIncomeSecuritiesStateAndMunicipal	11812000	USD
	us-gaap	Interest Income Securities State And Municipal InterestIncomeSecuritiesStateAndMunicipal	19065000	USD
	sbsi	Interest Income Other Stocks And Bonds InterestIncomeOtherStocksAndBonds	81000	USD
	sbsi	Interest Income Other Stocks And Bonds InterestIncomeOtherStocksAndBonds	84000	USD
	us-gaap	Interest Income Securities Mortgage Backed InterestIncomeSecuritiesMortgageBacked	38289000	USD
	us-gaap	Interest Income Securities Mortgage Backed InterestIncomeSecuritiesMortgageBacked	31190000	USD
	us-gaap	Interest And Other Income InterestAndOtherIncome	50182000	USD
	us-gaap	Interest And Other Income InterestAndOtherIncome	50569000	USD
	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	714000	USD
	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	5600000	USD
	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	4900000	USD
	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	-1900000	USD
	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	3800000	USD
	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	1900000	USD
	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	0	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	1263000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	1267000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	9177000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	9284000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	33327000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	34725000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	594532000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	617773000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities Single Maturity Date Amortized Cost Basis AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis	638299000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities Single Maturity Date AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate	663049000	USD
CY2019Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	2179809000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities Without Single Maturity Date Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost	1541510000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities Without Single Maturity Date Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue	1577332000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	2240381000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	115000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	116000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	1668000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	1683000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	1112000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	1129000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	0	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	0	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities Single Maturity Date Amortized Cost Basis HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis	2895000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities Single Maturity Date Fair Value HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValue	2928000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities Without Single Maturity Date Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithoutSingleMaturityDateNetCarryingAmount	138060000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities Without Single Maturity Date Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue	144112000	USD
CY2019Q3	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	140955000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	147040000	USD
CY2019Q3	us-gaap	Pledged Financial Instruments Not Separately Reported Securities Pledged PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesPledged	871900000	USD
CY2018Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Securities Pledged PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesPledged	1080000000.00	USD
CY2019Q3	us-gaap	Equity Securities Fv Ni And Without Readily Determinable Fair Value EquitySecuritiesFvNiAndWithoutReadilyDeterminableFairValue	12400000	USD
CY2018Q4	us-gaap	Equity Securities Fv Ni And Without Readily Determinable Fair Value EquitySecuritiesFvNiAndWithoutReadilyDeterminableFairValue	12100000	USD
CY2019Q3	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	-27000	USD
CY2018Q3	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	-42000	USD
	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	136000	USD
	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	-176000	USD
CY2019Q3	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	0	USD
CY2018Q3	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	0	USD
	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	0	USD
	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	0	USD
CY2019Q3	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	-27000	USD
CY2018Q3	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	-42000	USD
	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	136000	USD
	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	-176000	USD
CY2019Q3	sbsi	Equityinvestmentswithotherthantemporaryimpairment Equityinvestmentswithotherthantemporaryimpairment	0
CY2019Q3	sbsi	Federal Home Loan Bankstockwithotherthantemporaryimpairment FederalHomeLoanBankstockwithotherthantemporaryimpairment	0
CY2019Q3	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3499917000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3312799000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	25129000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	27019000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	3474788000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	3285780000	USD
CY2019Q2	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	24705000	USD
CY2019Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	1005000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	1000000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	419000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	25129000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	27019000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	2593000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	5682000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	1199000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	25129000	USD
CY2018Q2	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	25072000	USD
CY2018Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	975000	USD
CY2018Q3	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	662000	USD
CY2018Q3	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	707000	USD
CY2018Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	26092000	USD
CY2017Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	20781000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	5991000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	2346000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	1666000	USD
CY2018Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	26092000	USD
CY2019Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	1000000.0	USD
CY2019Q3	sbsi	Provision Reversalfor Pci Loans ProvisionReversalforPCILoans	2000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	2600000	USD
	sbsi	Provision Reversalfor Pci Loans ProvisionReversalforPCILoans	-161000	USD
CY2018Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	975000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	6000000.0	USD
CY2018Q3	sbsi	Provision Reversalfor Pci Loans ProvisionReversalforPCILoans	466000	USD
	sbsi	Provision Reversalfor Pci Loans ProvisionReversalforPCILoans	824000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	2129000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	23000000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	25129000	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
CY2019Q3	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	25477000	USD
CY2019Q3	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	3435001000	USD
CY2019Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet	39439000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3499917000	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
CY2019Q3	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3499917000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3312799000	USD
CY2019Q3	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	17148000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	35770000	USD
CY2019Q3	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
CY2019Q3	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	11683000	USD
CY2018Q4	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	5930000	USD
CY2019Q3	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	912000	USD
CY2018Q4	us-gaap	Other Foreclosed Assets OtherForeclosedAssets	0	USD
CY2019Q3	us-gaap	Notes Receivable Net NotesReceivableNet	29747000	USD
CY2018Q4	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	1206000	USD
CY2019Q3	us-gaap	Other Foreclosed Assets OtherForeclosedAssets	4000	USD
CY2018Q4	sbsi	Restructured Nonaccrual Loans RestructuredNonaccrualLoans	10900000	USD
CY2018Q4	us-gaap	Notes Receivable Net NotesReceivableNet	42906000	USD
CY2019Q3	sbsi	Restructured Nonaccrual Loans RestructuredNonaccrualLoans	8900000	USD
CY2019Q3	sbsi	Purchase Credit Impaired Loans Restructured PurchaseCreditImpairedLoansRestructured	757000	USD
CY2018Q4	sbsi	Purchase Credit Impaired Loans Restructured PurchaseCreditImpairedLoansRestructured	3100000	USD
CY2019Q3	sbsi	Loansin Processof Foreclosure LoansinProcessofForeclosure	781000	USD
CY2018Q4	sbsi	Loansin Processof Foreclosure LoansinProcessofForeclosure	147000	USD
CY2019Q3	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	17148000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	35770000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	0	USD
CY2019Q3	us-gaap	Impaired Financing Receivable Unpaid Principal Balance ImpairedFinancingReceivableUnpaidPrincipalBalance	39769000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	34080000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	2129000	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
CY2019Q3	sbsi	Purchase Credit Impaired Loanswith Deteriorationin Credit Quality After Acquisition PurchaseCreditImpairedLoanswithDeteriorationinCreditQualityAfterAcquisition	8600000	USD
CY2018Q4	sbsi	Purchase Credit Impaired Loanswith Deteriorationin Credit Quality After Acquisition PurchaseCreditImpairedLoanswithDeteriorationinCreditQualityAfterAcquisition	8000000.0	USD
CY2019Q3	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	17974000	USD
CY2019Q3	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	3481943000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	3499917000	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
CY2019Q3	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	34730000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable Interest Income Cash Basis Method ImpairedFinancingReceivableInterestIncomeCashBasisMethod	348000	USD
CY2018Q3	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	40061000	USD
CY2018Q3	us-gaap	Impaired Financing Receivable Interest Income Cash Basis Method ImpairedFinancingReceivableInterestIncomeCashBasisMethod	96000	USD
	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	39110000	USD
	us-gaap	Impaired Financing Receivable Interest Income Cash Basis Method ImpairedFinancingReceivableInterestIncomeCashBasisMethod	1098000	USD
	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	31034000	USD
	us-gaap	Impaired Financing Receivable Interest Income Cash Basis Method ImpairedFinancingReceivableInterestIncomeCashBasisMethod	252000	USD
CY2019Q3	sbsi	Loan Modification Related To Extending Amortization Period LoanModificationRelatedToExtendingAmortizationPeriod	0	USD
CY2019Q3	sbsi	Loanmodificationrelatedtointerestratesreductions Loanmodificationrelatedtointerestratesreductions	0	USD
CY2019Q3	sbsi	Loan Modification Extending Amortization Period Lowering Interest Rate And Principal Forgiveness LoanModificationExtendingAmortizationPeriodLoweringInterestRateAndPrincipalForgiveness	195000	USD
CY2019Q3	sbsi	Financing Receivable Modifications Total Modifications For Period FinancingReceivableModificationsTotalModificationsForPeriod	195000	USD
CY2019Q3	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	4	contract
	sbsi	Loan Modification Related To Extending Amortization Period LoanModificationRelatedToExtendingAmortizationPeriod	7615000	USD
	sbsi	Loanmodificationrelatedtointerestratesreductions Loanmodificationrelatedtointerestratesreductions	0	USD
	sbsi	Loan Modification Extending Amortization Period Lowering Interest Rate And Principal Forgiveness LoanModificationExtendingAmortizationPeriodLoweringInterestRateAndPrincipalForgiveness	902000	USD
	sbsi	Financing Receivable Modifications Total Modifications For Period FinancingReceivableModificationsTotalModificationsForPeriod	8517000	USD
	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	15	contract
CY2018Q3	sbsi	Loan Modification Related To Extending Amortization Period LoanModificationRelatedToExtendingAmortizationPeriod	142000	USD
CY2018Q3	sbsi	Loanmodificationrelatedtointerestratesreductions Loanmodificationrelatedtointerestratesreductions	35000	USD
CY2018Q3	sbsi	Loan Modification Extending Amortization Period Lowering Interest Rate And Principal Forgiveness LoanModificationExtendingAmortizationPeriodLoweringInterestRateAndPrincipalForgiveness	339000	USD
CY2018Q3	sbsi	Financing Receivable Modifications Total Modifications For Period FinancingReceivableModificationsTotalModificationsForPeriod	516000	USD
CY2018Q3	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	7	contract
	sbsi	Loan Modification Related To Extending Amortization Period LoanModificationRelatedToExtendingAmortizationPeriod	252000	USD
	sbsi	Loanmodificationrelatedtointerestratesreductions Loanmodificationrelatedtointerestratesreductions	115000	USD
	sbsi	Loan Modification Extending Amortization Period Lowering Interest Rate And Principal Forgiveness LoanModificationExtendingAmortizationPeriodLoweringInterestRateAndPrincipalForgiveness	431000	USD
	sbsi	Financing Receivable Modifications Total Modifications For Period FinancingReceivableModificationsTotalModificationsForPeriod	798000	USD
	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	16	contract
CY2019Q3	us-gaap	Loans And Leases Receivable Impaired Commitment To Lend LoansAndLeasesReceivableImpairedCommitmentToLend	0	USD
CY2019Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Outstanding Balance CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesOutstandingBalance	43654000	USD
CY2018Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Outstanding Balance CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesOutstandingBalance	51388000	USD
CY2019Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet	39439000	USD
CY2018Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Carrying Amount Net CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet	46402000	USD
CY2019Q2	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	14556000	USD
CY2018Q2	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	16105000	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
CY2019Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Period Increase Decrease CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldPeriodIncreaseDecrease	0	USD
CY2018Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Period Increase Decrease CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldPeriodIncreaseDecrease	0	USD
	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Period Increase Decrease CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldPeriodIncreaseDecrease	0	USD
CY2019Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Reclassifications To From Nonaccretable Difference CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldReclassificationsToFromNonaccretableDifference	258000	USD
CY2018Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Reclassifications To From Nonaccretable Difference CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldReclassificationsToFromNonaccretableDifference	620000	USD
	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Reclassifications To From Nonaccretable Difference CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldReclassificationsToFromNonaccretableDifference	1332000	USD
	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Reclassifications To From Nonaccretable Difference CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldReclassificationsToFromNonaccretableDifference	1389000	USD
CY2019Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	723000	USD
CY2018Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	733000	USD
	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	2295000	USD
	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	2673000	USD
CY2019Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	14091000	USD
CY2018Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	15992000	USD
CY2019Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	14091000	USD
CY2018Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	15992000	USD
CY2019Q3	sbsi	Borrowed Funds Maturities Repaymentsof Principalinthe Next Twelve Months BorrowedFundsMaturitiesRepaymentsofPrincipalintheNextTwelveMonths	971791000	USD
CY2019Q3	sbsi	Borrowed Funds Maturingin Year Two BorrowedFundsMaturinginYearTwo	11319000	USD
CY2019Q3	sbsi	Borrowed Funds Maturingin Year Three BorrowedFundsMaturinginYearThree	0	USD
CY2019Q3	sbsi	Borrowed Funds Maturingin Year Four BorrowedFundsMaturinginYearFour	0	USD
CY2019Q3	sbsi	Borrowed Funds Maturingin Year Five BorrowedFundsMaturinginYearFive	0	USD
CY2019Q3	sbsi	Borrowed Funds Maturing After Year Five BorrowedFundsMaturingAfterYearFive	5467000	USD
CY2019Q3	us-gaap	Debt And Capital Lease Obligations DebtAndCapitalLeaseObligations	988577000	USD
CY2019Q3	sbsi	Line Of Credit Facility Number Of Credit Lines Maintained By Company LineOfCreditFacilityNumberOfCreditLinesMaintainedByCompany	3	credit_line
CY2019Q3	us-gaap	Federal Funds Purchased FederalFundsPurchased	0	USD
CY2018Q4	us-gaap	Federal Funds Purchased FederalFundsPurchased	28000000.0	USD
CY2019Q3	us-gaap	Federal Home Loan Bank Advances General Debt Obligations Disclosures Amount Of Available Unused Funds FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresAmountOfAvailableUnusedFunds	1270000000	USD
CY2019Q3	sbsi	Letters Of Credit Fhlb As Collateral LettersOfCreditFhlbAsCollateral	0	USD
CY2019Q3	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	9600000	USD
CY2018Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	8800000	USD
	sbsi	Repurchase Agreement Counterparty Maturityof Agreements RepurchaseAgreementCounterpartyMaturityofAgreements	P10M
CY2019Q3	us-gaap	Subordinated Debt SubordinatedDebt	98532000	USD
CY2018Q4	us-gaap	Subordinated Debt SubordinatedDebt	98407000	USD
CY2019Q3	us-gaap	Other Long Term Debt OtherLongTermDebt	60249000	USD
CY2018Q4	us-gaap	Other Long Term Debt OtherLongTermDebt	60246000	USD
CY2019Q3	us-gaap	Long Term Debt LongTermDebt	158781000	USD
CY2018Q4	us-gaap	Long Term Debt LongTermDebt	158653000	USD
CY2019Q3	us-gaap	Debt Instrument Face Amount DebtInstrumentFaceAmount	270000000.0	USD
CY2019Q3	us-gaap	Collateral Already Posted Aggregate Fair Value CollateralAlreadyPostedAggregateFairValue	15700000	USD
CY2019Q3	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	12461000	USD
CY2019Q3	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	16665000	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
CY2019Q3	us-gaap	Derivative Asset Fair Value Gross Liability DerivativeAssetFairValueGrossLiability	964000	USD
CY2019Q3	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	964000	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
CY2019Q3	us-gaap	Derivative Asset Collateral Obligation To Return Cash Offset DerivativeAssetCollateralObligationToReturnCashOffset	0	USD
CY2019Q3	us-gaap	Derivative Liability Collateral Right To Reclaim Cash Offset DerivativeLiabilityCollateralRightToReclaimCashOffset	15701000	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
CY2019Q3	us-gaap	Derivative Assets DerivativeAssets	11497000	USD
CY2019Q3	us-gaap	Derivative Liabilities DerivativeLiabilities	0	USD
CY2018Q4	us-gaap	Derivative Assets DerivativeAssets	1087000	USD
CY2018Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	1119000	USD
CY2019Q3	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	3807000	USD
CY2018Q3	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	95000	USD
	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	10371000	USD
	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	3107000	USD
CY2019Q3	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-146000	USD
CY2018Q3	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	2097000	USD
	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-4000	USD
	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	4535000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3661000	USD
CY2018Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	2192000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10367000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	7642000	USD
CY2019Q3	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	8000000.0	USD
CY2018Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	9800000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3700000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10400000	USD
CY2018Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	2200000	USD
CY2019Q3	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.156
	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.153
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	7600000	USD
CY2018Q3	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.097
	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.119
	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Deferred Tax Asset Income Tax Expense TaxCutsAndJobsActOf2017ChangeInTaxRateDeferredTaxAssetIncomeTaxExpense	-800000	USD
CY2018Q3	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent	-0.036
	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent	-0.012
CY2019Q3	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	10046000	USD
CY2019Q3	us-gaap	Operating Lease Liability OperatingLeaseLiability	10478000	USD
CY2019Q3	us-gaap	Operating Lease Cost OperatingLeaseCost	400000	USD
	us-gaap	Operating Lease Cost OperatingLeaseCost	1189000	USD
CY2019Q3	us-gaap	Operating Lease Payments OperatingLeasePayments	359000	USD
	us-gaap	Operating Lease Payments OperatingLeasePayments	1059000	USD
CY2019Q3	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	537000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	1191000	USD
CY2019Q3	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P12Y2M12D
CY2019Q3	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0381	Rate
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Remainder Of Fiscal Year LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear	281000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	1456000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	1343000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	1232000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	1083000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	8126000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	13521000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	3043000	USD
CY2019Q3	us-gaap	Operating Lease Liability OperatingLeaseLiability	10478000	USD
CY2019Q3	sbsi	Lessee Operating Lease Lease Not Yet Commenced Payments Due LesseeOperatingLeaseLeaseNotYetCommencedPaymentsDue	9100000	USD
	sbsi	Lessee Operating Lease Not Yet Commenced Lease Term LesseeOperatingLeaseNotYetCommencedLeaseTerm	P20Y4M24D
CY2019Q3	us-gaap	Net Rentable Area NetRentableArea	202000	sqft
CY2019Q3	sbsi	Numberof Square Feet Occupied NumberofSquareFeetOccupied	41000	sqft
CY2019Q3	us-gaap	Operating Lease Lease Income OperatingLeaseLeaseIncome	767000	USD
	us-gaap	Operating Lease Lease Income OperatingLeaseLeaseIncome	2254000	USD
CY2019Q3	us-gaap	Lessor Operating Lease Payments To Be Received Remainder Of Fiscal Year LessorOperatingLeasePaymentsToBeReceivedRemainderOfFiscalYear	715000	USD
CY2019Q3	us-gaap	Lessor Operating Lease Payments To Be Received Two Years LessorOperatingLeasePaymentsToBeReceivedTwoYears	2847000	USD
CY2019Q3	us-gaap	Lessor Operating Lease Payments To Be Received Three Years LessorOperatingLeasePaymentsToBeReceivedThreeYears	1646000	USD
CY2019Q3	us-gaap	Lessor Operating Lease Payments To Be Received Four Years LessorOperatingLeasePaymentsToBeReceivedFourYears	1580000	USD
CY2019Q3	us-gaap	Lessor Operating Lease Payments To Be Received Five Years LessorOperatingLeasePaymentsToBeReceivedFiveYears	1344000	USD
CY2019Q3	us-gaap	Lessor Operating Lease Payments To Be Received Thereafter LessorOperatingLeasePaymentsToBeReceivedThereafter	4119000	USD
CY2019Q3	us-gaap	Lessor Operating Lease Payments To Be Received LessorOperatingLeasePaymentsToBeReceived	12251000	USD
CY2019Q3	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Amount Liability FairValueDisclosureOffbalanceSheetRisksAmountLiability	1010721000	USD
CY2018Q4	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Amount Liability FairValueDisclosureOffbalanceSheetRisksAmountLiability	901995000	USD
CY2019Q3	sbsi	Unsettled Trades To Purchase Securities Liability UnsettledTradesToPurchaseSecuritiesLiability	30300000	USD
CY2019Q3	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
CY2019Q3	sbsi	Unsettled Issuancesof Brokered C Ds UnsettledIssuancesofBrokeredCDs	0	USD
CY2018Q4	sbsi	Unsettled Issuancesof Brokered C Ds UnsettledIssuancesofBrokeredCDs	15200000	USD

Files In Submission

Name	View Source	Status
0000705432-19-000128-index-headers.html	Edgar Link	pending
0000705432-19-000128-index.html	Edgar Link	pending
0000705432-19-000128.txt	Edgar Link	pending
0000705432-19-000128-xbrl.zip	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
R1.htm	Edgar Link	pending
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report.css	Edgar Link	pending
sbsi-20190930.xsd	Edgar Link	pending
sbsi-20190930_cal.xml	Edgar Link	unprocessable
sbsi-20190930_def.xml	Edgar Link	unprocessable
sbsi-20190930_lab.xml	Edgar Link	unprocessable
sbsi-20190930_pre.xml	Edgar Link	unprocessable
sbsi093019ex311.htm	Edgar Link	pending
sbsi093019ex312.htm	Edgar Link	pending
sbsi093019ex32.htm	Edgar Link	pending
sbsi10-q093019.htm	Edgar Link	pending
sbsi10-q093019_htm.xml	Edgar Link	completed
Show.js	Edgar Link	pending

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$SBSI
SOUTHSIDE BANCSHARES INC Stock $sbsi

2019 Q4 Form 10-Q Financial Statement

#000070543219000128 Filed on October 31, 2019

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SBSI SOUTHSIDE BANCSHARES INC Stock $sbsi

2019 Q4 Form 10-Q Financial Statement

#000070543219000128 Filed on October 31, 2019

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SBSI
SOUTHSIDE BANCSHARES INC Stock $sbsi