$OTTR
Otter Tail Corp Stock $ottr

$ottr Overview Financials Valuation SEC Filings Company Website

2018 Q4 Form 10-K Financial Statement

#000143774920003157 Filed on February 20, 2020

Income Statement

Concept	2018 Q4	2017 Q4	2017
Revenue	$221.2M	$206.7M	$849.4M
YoY Change	7.01%	5.14%	5.7%
Cost Of Revenue	$101.6M	$86.90M	$316.6M
YoY Change	16.92%	1.05%	7.23%
Gross Profit	$119.6M	$119.8M	$532.8M
YoY Change	-0.17%	8.32%	4.81%
Gross Profit Margin	54.07%	57.96%	62.73%
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$18.50M	$18.80M	$72.55M
YoY Change	-1.6%	2.73%	-1.23%
% of Gross Profit	15.47%	15.69%	13.62%
Operating Expenses	$96.20M	$81.50M	$335.7M
YoY Change	18.04%	0.0%	0.51%
Operating Profit	$23.40M	$38.30M	$132.3M
YoY Change	-38.9%	31.62%	13.42%
Interest Expense	-$7.800M	-$7.200M	-$29.60M
YoY Change	8.33%	-8.86%	-7.21%
% of Operating Profit	-33.33%	-18.8%	-22.38%
Other Income/Expense, Net	-$1.100M	-$4.700M	$2.632M
YoY Change	-76.6%	-1040.0%	-9.4%
Pretax Income	$14.50M	$26.40M	$99.70M
YoY Change	-45.08%	21.66%	20.78%
Income Tax	$400.0K	$6.200M	$27.26M
% Of Pretax Income	2.76%	23.48%	27.34%
Net Earnings	$14.20M	$18.40M	$72.44M
YoY Change	-22.83%	5.14%	16.24%
Net Earnings / Revenue	6.42%	8.9%	8.53%
Basic Earnings Per Share			$1.84
Diluted Earnings Per Share	$355.9K	$461.2K	$1.82
COMMON SHARES
Basic Shares Outstanding			39.46M
Diluted Shares Outstanding			39.75M

Balance Sheet

Concept	2018 Q4	2017 Q4	2017
SHORT-TERM ASSETS
Cash & Short-Term Investments	$900.0K	$16.20M	$16.20M
YoY Change	-94.44%
Cash & Equivalents	$861.0K	$16.22M	$16.20M
Short-Term Investments
Other Short-Term Assets	$6.114M	$12.49M	$57.50M
YoY Change	-51.05%	53.38%	16.16%
Inventory	$106.3M	$88.03M	$88.00M
Prepaid Expenses
Receivables	$75.14M	$68.47M	$68.50M
Other Receivables	$9.741M	$7.761M	$8.900M
Total Short-Term Assets	$241.4M	$239.1M	$239.1M
YoY Change	0.96%	14.96%	14.95%
LONG-TERM ASSETS
Property, Plant & Equipment	$1.581B	$1.540B	$1.540B
YoY Change	2.7%	4.22%	4.22%
Goodwill	$37.57M	$37.57M
YoY Change	0.0%	0.0%
Intangibles	$12.45M	$13.77M
YoY Change	-9.55%	-7.98%
Long-Term Investments	$9.000M	$8.600M	$8.600M
YoY Change	4.65%	2.38%	2.38%
Other Assets	$35.76M	$36.01M	$165.6M
YoY Change	-0.69%	5.58%	-0.36%
Total Long-Term Assets	$1.811B	$1.765B	$1.765B
YoY Change	2.6%	3.57%	3.57%
TOTAL ASSETS
Total Short-Term Assets	$241.4M	$239.1M	$239.1M
Total Long-Term Assets	$1.811B	$1.765B	$1.765B
Total Assets	$2.053B	$2.004B	$2.004B
YoY Change	2.41%	4.81%	4.81%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$96.29M	$84.68M	$84.20M
YoY Change	13.72%	-5.23%	-5.82%
Accrued Expenses	$37.00M	$32.90M	$32.90M
YoY Change	12.46%	0.0%	0.0%
Deferred Revenue
YoY Change
Short-Term Debt	$18.60M	$112.4M	$112.4M
YoY Change	-83.45%	162.04%	162.0%
Long-Term Debt Due	$172.0K	$186.0K	$200.0K
YoY Change	-7.53%	-99.44%	-99.4%
Total Short-Term Liabilities	$170.1M	$256.7M	$256.7M
YoY Change	-33.73%	19.0%	19.01%
LONG-TERM LIABILITIES
Long-Term Debt	$590.0M	$490.4M	$490.4M
YoY Change	20.32%	-2.96%	-2.95%
Other Long-Term Liabilities	$24.33M	$22.77M	$438.5M
YoY Change	6.84%	4.9%	61.33%
Total Long-Term Liabilities	$614.3M	$513.1M	$928.9M
YoY Change	19.72%	-2.64%	19.53%
TOTAL LIABILITIES
Total Short-Term Liabilities	$170.1M	$256.7M	$256.7M
Total Long-Term Liabilities	$614.3M	$513.1M	$928.9M
Total Liabilities	$784.4M	$769.8M	$1.307B
YoY Change	1.9%	3.65%	5.24%
SHAREHOLDERS EQUITY
Retained Earnings	$190.4M	$161.3M
YoY Change	18.07%	15.63%
Common Stock	$542.6M	$541.2M
YoY Change	0.25%	1.27%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$728.9M	$696.9M	$696.9M
YoY Change
Total Liabilities & Shareholders Equity	$2.053B	$2.004B	$2.004B
YoY Change	2.41%	4.81%	4.81%

Cashflow Statement

Concept	2018 Q4	2017 Q4	2017
OPERATING ACTIVITIES
Net Income	$14.20M	$18.40M	$72.44M
YoY Change	-22.83%	5.14%	16.24%
Depreciation, Depletion And Amortization	$18.50M	$18.80M	$72.55M
YoY Change	-1.6%	2.73%	-1.23%
Cash From Operating Activities	$42.50M	$59.50M	$173.6M
YoY Change	-28.57%	22.18%	6.24%
INVESTING ACTIVITIES
Capital Expenditures	-$30.90M	-$38.40M	-$132.9M
YoY Change	-19.53%	8.47%	-17.61%
Acquisitions
YoY Change
Other Investing Activities	-$600.0K	$1.000M	$300.0K
YoY Change	-160.0%	-266.67%	-84.21%
Cash From Investing Activities	-$31.50M	-$37.30M	-$132.6M
YoY Change	-15.55%	3.9%	-16.78%
FINANCING ACTIVITIES
Cash Dividend Paid			$50.63M
YoY Change
Common Stock Issuance & Retirement, Net			-$2.550M
YoY Change			-94.25%
Debt Paid & Issued, Net			$48.23M
YoY Change			-44.91%
Cash From Financing Activities	-10.90M	-6.800M	-$24.77M
YoY Change	60.29%	-46.87%	509.82%
NET CHANGE
Cash From Operating Activities	42.50M	59.50M	$173.6M
Cash From Investing Activities	-31.50M	-37.30M	-$132.6M
Cash From Financing Activities	-10.90M	-6.800M	-$24.77M
Net Change In Cash	100.0K	15.40M	$16.22M
YoY Change	-99.35%	826781204479999900.0%
FREE CASH FLOW
Cash From Operating Activities	$42.50M	$59.50M	$173.6M
Capital Expenditures	-$30.90M	-$38.40M	-$132.9M
Free Cash Flow	$73.40M	$97.90M	$306.5M
YoY Change	-25.03%	16.41%	-5.61%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2018Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	1407000	USD
CY2019Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	5
CY2020Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	40214375
CY2019	ottr	Standard Product Warranty Term StandardProductWarrantyTerm	P1Y
CY2019	us-gaap	Standard Product Warranty Accrual Payments StandardProductWarrantyAccrualPayments	0	USD
CY2017	us-gaap	Standard Product Warranty Accrual Payments StandardProductWarrantyAccrualPayments	0	USD
CY2018	us-gaap	Standard Product Warranty Accrual Payments StandardProductWarrantyAccrualPayments	0	USD
CY2018	ottr	Maximum Per Share Differences Between Basic And Diluted Earnings Per Share In Total Or From Continuing Or Discontinued Operations MaximumPerShareDifferencesBetweenBasicAndDilutedEarningsPerShareInTotalOrFromContinuingOrDiscontinuedOperations	0.016
CY2017	ottr	Maximum Per Share Differences Between Basic And Diluted Earnings Per Share In Total Or From Continuing Or Discontinued Operations MaximumPerShareDifferencesBetweenBasicAndDilutedEarningsPerShareInTotalOrFromContinuingOrDiscontinuedOperations	0.016
CY2017	us-gaap	Operating Lease Expense OperatingLeaseExpense	6237000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21	pure
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	1339000	USD
CY2018Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	5
CY2019Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	50000000
CY2018Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	50000000
CY2019Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	40157591
CY2018Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	39664884
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	21199000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	861000	USD
CY2019Q4	ottr	Public Utilities Property Plant And Equipment Electric PublicUtilitiesPropertyPlantAndEquipmentElectric	2212884000	USD
CY2018Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	24857000	USD
CY2019Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	11290000	USD
CY2018Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	12450000	USD
CY2018Q4	us-gaap	Assets Assets	2052517000	USD
CY2019Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	6000000	USD
CY2019Q4	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	144138000	USD
CY2018Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	18599000	USD
CY2018Q4	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	135257000	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	21851000	USD
CY2019Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	183000	USD
CY2018Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	172000	USD
CY2019Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	120775000	USD
CY2018Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	96291000	USD
CY2019Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	22730000	USD
CY2018Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	0	USD
CY2019Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	77947000	USD
CY2018Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	75144000	USD
CY2019Q4	us-gaap	Other Receivables Net Current OtherReceivablesNetCurrent	8773000	USD
CY2018Q4	us-gaap	Other Receivables Net Current OtherReceivablesNetCurrent	9741000	USD
CY2019Q4	us-gaap	Inventory Net InventoryNet	97851000	USD
CY2018Q4	us-gaap	Inventory Net InventoryNet	106270000	USD
CY2019Q4	us-gaap	Unbilled Receivables Current UnbilledReceivablesCurrent	20911000	USD
CY2018Q4	us-gaap	Unbilled Receivables Current UnbilledReceivablesCurrent	23626000	USD
CY2019Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	1487000	USD
CY2018Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	2439000	USD
CY2019Q4	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	21650000	USD
CY2018Q4	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	17225000	USD
CY2019Q4	us-gaap	Other Assets Current OtherAssetsCurrent	5042000	USD
CY2018Q4	us-gaap	Other Assets Current OtherAssetsCurrent	6114000	USD
CY2019Q4	us-gaap	Assets Current AssetsCurrent	254860000	USD
CY2018Q4	us-gaap	Assets Current AssetsCurrent	241420000	USD
CY2019Q4	us-gaap	Long Term Investments LongTermInvestments	9894000	USD
CY2018Q4	us-gaap	Long Term Investments LongTermInvestments	8961000	USD
CY2019Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	40196000	USD
CY2018Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	35759000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	37572000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	37572000	USD
CY2018Q4	ottr	Public Utilities Property Plant And Equipment Electric PublicUtilitiesPropertyPlantAndEquipmentElectric	2019721000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Other PropertyPlantAndEquipmentOther	247356000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Other PropertyPlantAndEquipmentOther	228120000	USD
CY2019Q4	us-gaap	Construction In Progress Gross ConstructionInProgressGross	185238000	USD
CY2018Q4	us-gaap	Construction In Progress Gross ConstructionInProgressGross	181626000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	2645478000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	2429467000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	891684000	USD
CY2018Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	848369000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1753794000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1581098000	USD
CY2019Q4	us-gaap	Assets Assets	2273595000	USD
CY2019Q4	us-gaap	Accrual For Taxes Other Than Income Taxes Current AccrualForTaxesOtherThanIncomeTaxesCurrent	17525000	USD
CY2018Q4	us-gaap	Accrual For Taxes Other Than Income Taxes Current AccrualForTaxesOtherThanIncomeTaxesCurrent	17287000	USD
CY2019Q4	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	7480000	USD
CY2018Q4	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	738000	USD
CY2019Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	4136000	USD
CY2018Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	0	USD
CY2019Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	10912000	USD
CY2018Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	12149000	USD
CY2019Q4	us-gaap	Liabilities Current LiabilitiesCurrent	189741000	USD
CY2018Q4	us-gaap	Liabilities Current LiabilitiesCurrent	170093000	USD
CY2019Q4	us-gaap	Defined Benefit Pension Plan Liabilities Noncurrent DefinedBenefitPensionPlanLiabilitiesNoncurrent	98970000	USD
CY2018Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	190433000	USD
CY2019Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	222341000	USD
CY2018Q4	us-gaap	Defined Benefit Pension Plan Liabilities Noncurrent DefinedBenefitPensionPlanLiabilitiesNoncurrent	98358000	USD
CY2019Q4	us-gaap	Other Postretirement Defined Benefit Plan Liabilities Noncurrent OtherPostretirementDefinedBenefitPlanLiabilitiesNoncurrent	71437000	USD
CY2018Q4	us-gaap	Other Postretirement Defined Benefit Plan Liabilities Noncurrent OtherPostretirementDefinedBenefitPlanLiabilitiesNoncurrent	71561000	USD
CY2019Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	18193000	USD
CY2018Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	0	USD
CY2019Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	30833000	USD
CY2018Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	24326000	USD
CY2019Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2018Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	131941000	USD
CY2018Q4	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	120976000	USD
CY2019Q4	us-gaap	Accumulated Deferred Investment Tax Credit AccumulatedDeferredInvestmentTaxCredit	18626000	USD
CY2018Q4	us-gaap	Accumulated Deferred Investment Tax Credit AccumulatedDeferredInvestmentTaxCredit	19974000	USD
CY2019Q4	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	239906000	USD
CY2018Q4	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	226469000	USD
CY2019Q4	ottr	Other Contracts With Customer Liability Noncurrent OtherContractsWithCustomerLiabilityNoncurrent	2885000	USD
CY2018Q4	ottr	Other Contracts With Customer Liability Noncurrent OtherContractsWithCustomerLiabilityNoncurrent	1895000	USD
CY2019Q4	ottr	Total Deferred Credits And Liabilities TotalDeferredCreditsAndLiabilities	393358000	USD
CY2018Q4	ottr	Total Deferred Credits And Liabilities TotalDeferredCreditsAndLiabilities	369314000	USD
CY2019Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	689581000	USD
CY2018Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	590002000	USD
CY2019Q4	us-gaap	Common Stock Value CommonStockValue	200788000	USD
CY2018Q4	us-gaap	Common Stock Value CommonStockValue	198324000	USD
CY2019Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	364790000	USD
CY2018Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	344250000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-6437000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-4144000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	781482000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	728863000	USD
CY2019Q4	us-gaap	Capitalization Longterm Debt And Equity CapitalizationLongtermDebtAndEquity	1471063000	USD
CY2018Q4	us-gaap	Capitalization Longterm Debt And Equity CapitalizationLongtermDebtAndEquity	1318865000	USD
CY2019Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	2273595000	USD
CY2018Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	2052517000	USD
CY2019	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	919503000	USD
CY2018	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	916447000	USD
CY2017	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	849350000	USD
CY2019	us-gaap	Utilities Operating Expense Fuel Used UtilitiesOperatingExpenseFuelUsed	59256000	USD
CY2018	us-gaap	Utilities Operating Expense Fuel Used UtilitiesOperatingExpenseFuelUsed	66815000	USD
CY2017	us-gaap	Utilities Operating Expense Fuel Used UtilitiesOperatingExpenseFuelUsed	59690000	USD
CY2019	us-gaap	Utilities Operating Expense Maintenance And Operations UtilitiesOperatingExpenseMaintenanceAndOperations	153529000	USD
CY2018	us-gaap	Utilities Operating Expense Maintenance And Operations UtilitiesOperatingExpenseMaintenanceAndOperations	155534000	USD
CY2017	us-gaap	Utilities Operating Expense Maintenance And Operations UtilitiesOperatingExpenseMaintenanceAndOperations	146914000	USD
CY2019	us-gaap	Utilities Operating Expense Products And Services UtilitiesOperatingExpenseProductsAndServices	355119000	USD
CY2018	us-gaap	Utilities Operating Expense Products And Services UtilitiesOperatingExpenseProductsAndServices	354559000	USD
CY2017	us-gaap	Utilities Operating Expense Products And Services UtilitiesOperatingExpenseProductsAndServices	316562000	USD
CY2019	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	50782000	USD
CY2018	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	51544000	USD
CY2017	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	41492000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	78086000	USD
CY2018	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	74666000	USD
CY2017	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	72545000	USD
CY2019	us-gaap	Utilities Operating Expense Other UtilitiesOperatingExpenseOther	15785000	USD
CY2018	us-gaap	Utilities Operating Expense Other UtilitiesOperatingExpenseOther	15585000	USD
CY2017	us-gaap	Utilities Operating Expense Other UtilitiesOperatingExpenseOther	15053000	USD
CY2019	us-gaap	Costs And Expenses CostsAndExpenses	784623000	USD
CY2018	us-gaap	Costs And Expenses CostsAndExpenses	787058000	USD
CY2017	us-gaap	Costs And Expenses CostsAndExpenses	717063000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	134880000	USD
CY2018	us-gaap	Operating Income Loss OperatingIncomeLoss	129389000	USD
CY2017	us-gaap	Operating Income Loss OperatingIncomeLoss	132287000	USD
CY2019	us-gaap	Interest And Debt Expense InterestAndDebtExpense	31411000	USD
CY2018	us-gaap	Interest And Debt Expense InterestAndDebtExpense	30408000	USD
CY2018	us-gaap	Net Periodic Defined Benefits Expense Reversal Of Expense Excluding Service Cost Component NetPeriodicDefinedBenefitsExpenseReversalOfExpenseExcludingServiceCostComponent	5509000	USD
CY2019	ottr	Other Comprehensive Income Deferred Tax Rate Adjustment OtherComprehensiveIncomeDeferredTaxRateAdjustment	0	USD
CY2017	us-gaap	Interest And Debt Expense InterestAndDebtExpense	29604000	USD
CY2019	us-gaap	Net Periodic Defined Benefits Expense Reversal Of Expense Excluding Service Cost Component NetPeriodicDefinedBenefitsExpenseReversalOfExpenseExcludingServiceCostComponent	4293000	USD
CY2017	us-gaap	Net Periodic Defined Benefits Expense Reversal Of Expense Excluding Service Cost Component NetPeriodicDefinedBenefitsExpenseReversalOfExpenseExcludingServiceCostComponent	5620000	USD
CY2018	ottr	Other Comprehensive Income Deferred Tax Rate Adjustment OtherComprehensiveIncomeDeferredTaxRateAdjustment	-531000	USD
CY2017	ottr	Other Comprehensive Income Deferred Tax Rate Adjustment OtherComprehensiveIncomeDeferredTaxRateAdjustment	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	1638000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	17441000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	1919000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14588000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	27256000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	86847000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	82345000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	72439000	USD
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	39721000
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	39600000
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	39457000
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-3791000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	565000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	985000	USD
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	39954000
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	39892000
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	39748000
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.19
CY2017	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	629000	USD
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.08
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.84
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.17
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.06
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.82
CY2019	us-gaap	Net Income Loss NetIncomeLoss	86847000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	82345000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	576000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-755000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	1266000	USD
CY2019	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	5112000	USD
CY2018	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	3461000	USD
CY2017	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	2632000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	104288000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	96933000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	99695000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	72439000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-16000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	105000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	15000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	147000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-61000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	115000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	34000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-35000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	35000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	129000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-131000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	65000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-2779000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1618000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	1896000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-1509000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	1487000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-1831000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	85338000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	83832000	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	70608000	USD
CY2016Q4	us-gaap	Stockholders Equity StockholdersEquity	670104000	USD
CY2017	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	4969000	USD
CY2017	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	1799000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	72439000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-1831000	USD
CY2017	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	3642000	USD
CY2017	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	50632000	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	696892000	USD
CY2018	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	-93000	USD
CY2018	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	3011000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	82345000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	1487000	USD
CY2018	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	4441000	USD
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	53198000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	728863000	USD
CY2019	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	19776000	USD
CY2019	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	2730000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	86847000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-1509000	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	5958000	USD
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	55723000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	781482000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	86847000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	82345000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	72439000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	78086000	USD
CY2018	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	74666000	USD
CY2017	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	72545000	USD
CY2019	us-gaap	Income Tax Credits And Adjustments IncomeTaxCreditsAndAdjustments	-1348000	USD
CY2018	us-gaap	Income Tax Credits And Adjustments IncomeTaxCreditsAndAdjustments	-1405000	USD
CY2017	us-gaap	Income Tax Credits And Adjustments IncomeTaxCreditsAndAdjustments	-1470000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	11507000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	19224000	USD
CY2017	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	24001000	USD
CY2019	ottr	Increase Decrease In Deferred Charges And Other Assets IncreaseDecreaseInDeferredChargesAndOtherAssets	-15502000	USD
CY2018	ottr	Increase Decrease In Deferred Charges And Other Assets IncreaseDecreaseInDeferredChargesAndOtherAssets	941000	USD
CY2017	ottr	Increase Decrease In Deferred Charges And Other Assets IncreaseDecreaseInDeferredChargesAndOtherAssets	-2173000	USD
CY2019	us-gaap	Pension Contributions PensionContributions	22500000	USD
CY2018	us-gaap	Pension Contributions PensionContributions	20000000	USD
CY2017	us-gaap	Pension Contributions PensionContributions	-0	USD
CY2019	ottr	Increase Decrease In Other Operating Liabilities And Increase Decrease In Deferred Liabilities IncreaseDecreaseInOtherOperatingLiabilitiesAndIncreaseDecreaseInDeferredLiabilities	-33534000	USD
CY2018	ottr	Increase Decrease In Other Operating Liabilities And Increase Decrease In Deferred Liabilities IncreaseDecreaseInOtherOperatingLiabilitiesAndIncreaseDecreaseInDeferredLiabilities	2414000	USD
CY2017	ottr	Increase Decrease In Other Operating Liabilities And Increase Decrease In Deferred Liabilities IncreaseDecreaseInOtherOperatingLiabilitiesAndIncreaseDecreaseInDeferredLiabilities	-19257000	USD
CY2019	us-gaap	Increase Decrease In Allowance For Equity Funds Used During Construction IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction	2553000	USD
CY2018	us-gaap	Increase Decrease In Allowance For Equity Funds Used During Construction IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction	2194000	USD
CY2017	us-gaap	Increase Decrease In Allowance For Equity Funds Used During Construction IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction	986000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	5958000	USD
CY2017	us-gaap	Payments Of Stock Issuance Costs PaymentsOfStockIssuanceCosts	-0	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	4441000	USD
CY2017	us-gaap	Share Based Compensation ShareBasedCompensation	3642000	USD
CY2019	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-76000	USD
CY2018	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-0	USD
CY2017	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-10000	USD
CY2019	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	1860000	USD
CY2018	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	8559000	USD
CY2017	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	2135000	USD
CY2019	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-8419000	USD
CY2018	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	18236000	USD
CY2017	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	4294000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-2919000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	754000	USD
CY2017	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	3060000	USD
CY2019	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-171000	USD
CY2018	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	14997000	USD
CY2017	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-3013000	USD
CY2019	ottr	Increase Decrease In Interest Payable And Income Taxes Receivable Payable Net IncreaseDecreaseInInterestPayableAndIncomeTaxesReceivablePayableNet	1625000	USD
CY2018	ottr	Increase Decrease In Interest Payable And Income Taxes Receivable Payable Net IncreaseDecreaseInInterestPayableAndIncomeTaxesReceivablePayableNet	396000	USD
CY2017	ottr	Increase Decrease In Interest Payable And Income Taxes Receivable Payable Net IncreaseDecreaseInInterestPayableAndIncomeTaxesReceivablePayableNet	-1186000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	185037000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	143448000	USD
CY2017	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	173577000	USD
CY2019	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	207365000	USD
CY2018	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	105425000	USD
CY2017	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	132913000	USD
CY2019	us-gaap	Proceeds From Sale Of Productive Assets ProceedsFromSaleOfProductiveAssets	8519000	USD
CY2018	us-gaap	Proceeds From Sale Of Productive Assets ProceedsFromSaleOfProductiveAssets	2378000	USD
CY2017	us-gaap	Proceeds From Sale Of Productive Assets ProceedsFromSaleOfProductiveAssets	4491000	USD
CY2019	us-gaap	Payments For Proceeds From Investments PaymentsForProceedsFromInvestments	10626000	USD
CY2018	us-gaap	Payments For Proceeds From Investments PaymentsForProceedsFromInvestments	4372000	USD
CY2017	us-gaap	Payments For Proceeds From Investments PaymentsForProceedsFromInvestments	4168000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-209472000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-107419000	USD
CY2017	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-132590000	USD
CY2019	ottr	Change In Checks Written In Excess Of Cash ChangeInChecksWrittenInExcessOfCash	2814000	USD
CY2018	ottr	Change In Checks Written In Excess Of Cash ChangeInChecksWrittenInExcessOfCash	345000	USD
CY2017	ottr	Change In Checks Written In Excess Of Cash ChangeInChecksWrittenInExcessOfCash	-2434000	USD
CY2019	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-12599000	USD
CY2018	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-93772000	USD
CY2017	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	69488000	USD
CY2019	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	20338000	USD
CY2018	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	0	USD
CY2017	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	4349000	USD
CY2019	us-gaap	Payments Of Stock Issuance Costs PaymentsOfStockIssuanceCosts	577000	USD
CY2018	us-gaap	Payments Of Stock Issuance Costs PaymentsOfStockIssuanceCosts	108000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	2730000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	3011000	USD
CY2017	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	1799000	USD
CY2019	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	100000000	USD
CY2018	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	100000000	USD
CY2017	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	0	USD
CY2019	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	950000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	861000	USD
CY2017Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	16216000	USD
CY2018	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	761000	USD
CY2017	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	380000	USD
CY2019	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	172000	USD
CY2018	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	189000	USD
CY2017	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	48231000	USD
CY2019	us-gaap	Payments Of Dividends PaymentsOfDividends	55723000	USD
CY2018	us-gaap	Payments Of Dividends PaymentsOfDividends	53198000	USD
CY2017	us-gaap	Payments Of Dividends PaymentsOfDividends	50632000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	44773000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-51384000	USD
CY2017	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-24771000	USD
CY2019	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	20338000	USD
CY2018	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-15355000	USD
CY2017	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	16216000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	861000	USD
CY2017Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	16216000	USD
CY2016Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	0	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	21199000	USD
CY2019Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	6000000	USD
CY2018Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	18599000	USD
CY2019Q4	us-gaap	Long Term Debt LongTermDebt	692351000	USD
CY2018Q4	us-gaap	Long Term Debt LongTermDebt	592523000	USD
CY2019Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	183000	USD
CY2018Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	172000	USD
CY2019Q4	us-gaap	Debt Instrument Unamortized Discount DebtInstrumentUnamortizedDiscount	2587000	USD
CY2018Q4	us-gaap	Debt Instrument Unamortized Discount DebtInstrumentUnamortizedDiscount	2349000	USD
CY2019Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	689581000	USD
CY2018Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	590002000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	781482000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	728863000	USD
CY2019Q4	us-gaap	Capitalization Longterm Debt And Equity CapitalizationLongtermDebtAndEquity	1471063000	USD
CY2018Q4	us-gaap	Capitalization Longterm Debt And Equity CapitalizationLongtermDebtAndEquity	1318865000	USD
CY2019Q4	us-gaap	Inventory Net InventoryNet	97851000	USD
CY2018Q4	us-gaap	Inventory Net InventoryNet	106270000	USD
CY2019Q4	us-gaap	Inventory Work In Process InventoryWorkInProcess	16508000	USD
CY2018Q4	us-gaap	Inventory Work In Process InventoryWorkInProcess	20393000	USD
CY2019Q4	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	49480000	USD
CY2018Q4	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	48747000	USD
CY2019	us-gaap	Use Of Estimates UseOfEstimates	<p style="font-family: "Times New Roman", Times, serif; font-size: 10pt; margin: 0pt; text-align: left;"><span style="text-decoration: underline; ">Use of Estimates</span></p> <p style="font-family: "Times New Roman", Times, serif; font-size: 10pt; margin: 0pt; text-align: left;">The Company uses estimates based on the best information available in recording transactions and balances resulting from business operations. As better information becomes available (or actual amounts are known), the recorded estimates are revised. Consequently, operating results can be affected by revisions to prior accounting estimates.</p>
CY2019Q4	us-gaap	Investments Investments	9894000	USD
CY2018Q4	us-gaap	Investments Investments	8961000	USD
CY2019Q4	us-gaap	Inventory Finished Goods Net Of Reserves InventoryFinishedGoodsNetOfReserves	31863000	USD
CY2018Q4	us-gaap	Inventory Finished Goods Net Of Reserves InventoryFinishedGoodsNetOfReserves	37130000	USD
CY2018Q4	us-gaap	Goodwill Gross GoodwillGross	37572000	USD
CY2018Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	0	USD
CY2018Q4	us-gaap	Goodwill Goodwill	37572000	USD
CY2019	us-gaap	Goodwill Period Increase Decrease GoodwillPeriodIncreaseDecrease	0	USD
CY2019Q4	us-gaap	Goodwill Goodwill	37572000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	1104000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	1099000	USD
CY2018	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	74666000	USD
CY2017	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	72545000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	72439000	USD
CY2019	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	207365000	USD
CY2017Q4	us-gaap	Goodwill Gross GoodwillGross	37572000	USD
CY2017Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	0	USD
CY2017Q4	us-gaap	Goodwill Goodwill	37572000	USD
CY2018	us-gaap	Goodwill Period Increase Decrease GoodwillPeriodIncreaseDecrease	0	USD
CY2018Q4	us-gaap	Goodwill Goodwill	37572000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	22670000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	11380000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	11290000	USD
CY2018Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	22645000	USD
CY2018Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	10195000	USD
CY2018Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	12450000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1186000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1315000	USD
CY2017	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1347000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Remainder Of Fiscal Year FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear	1140000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	1105000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	1105000	USD
CY2017	us-gaap	Interest Paid Net InterestPaidNet	29791000	USD
CY2017	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	41492000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	78086000	USD
CY2019	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	4797000	USD
CY2018	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	6109000	USD
CY2017	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	5064000	USD
CY2019Q4	ottr	Accounts Payable Outstanding Related To Capital Additions AccountsPayableOutstandingRelatedToCapitalAdditions	37429000	USD
CY2018Q4	ottr	Accounts Payable Outstanding Related To Capital Additions AccountsPayableOutstandingRelatedToCapitalAdditions	13757000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	30132000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	28109000	USD
CY2019	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	3	pure
CY2019	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	919503000	USD
CY2018	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	916447000	USD
CY2017	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	849350000	USD
CY2019	us-gaap	Utilities Operating Expense Products And Services UtilitiesOperatingExpenseProductsAndServices	355119000	USD
CY2018	us-gaap	Utilities Operating Expense Products And Services UtilitiesOperatingExpenseProductsAndServices	354559000	USD
CY2017	us-gaap	Utilities Operating Expense Products And Services UtilitiesOperatingExpenseProductsAndServices	316562000	USD
CY2019	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	50782000	USD
CY2018	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	51544000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	134880000	USD
CY2018	us-gaap	Operating Income Loss OperatingIncomeLoss	129389000	USD
CY2017	us-gaap	Operating Income Loss OperatingIncomeLoss	132287000	USD
CY2019	us-gaap	Interest And Debt Expense InterestAndDebtExpense	31411000	USD
CY2018	us-gaap	Interest And Debt Expense InterestAndDebtExpense	30408000	USD
CY2017	us-gaap	Interest And Debt Expense InterestAndDebtExpense	29604000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	17441000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14588000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	27256000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	86847000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	82345000	USD
CY2018Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	39664884
CY2019	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	29599
CY2018	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	105425000	USD
CY2017	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	132913000	USD
CY2019Q4	us-gaap	Assets Assets	2273595000	USD
CY2018Q4	us-gaap	Assets Assets	2052517000	USD
CY2017Q4	us-gaap	Assets Assets	2004278000	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.35	pure
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21	pure
CY2019Q4	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	21650000	USD
CY2019Q4	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	144138000	USD
CY2019Q4	us-gaap	Regulatory Assets RegulatoryAssets	165788000	USD
CY2019Q4	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	7480000	USD
CY2019Q4	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	239906000	USD
CY2019Q4	us-gaap	Regulatory Liabilities RegulatoryLiabilities	247386000	USD
CY2019Q4	ottr	Net Regulatory Assets Liability Current NetRegulatoryAssetsLiabilityCurrent	14170000	USD
CY2019Q4	ottr	Net Regulatory Assets Liability Noncurrent NetRegulatoryAssetsLiabilityNoncurrent	-95768000	USD
CY2019Q4	us-gaap	Net Regulatory Assets NetRegulatoryAssets	-81598000	USD
CY2018Q4	us-gaap	Regulatory Assets Current RegulatoryAssetsCurrent	17225000	USD
CY2018Q4	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	135257000	USD
CY2018Q4	us-gaap	Regulatory Assets RegulatoryAssets	152482000	USD
CY2018Q4	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	738000	USD
CY2018Q4	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	226469000	USD
CY2018Q4	us-gaap	Regulatory Liabilities RegulatoryLiabilities	227207000	USD
CY2018Q4	ottr	Net Regulatory Assets Liability Current NetRegulatoryAssetsLiabilityCurrent	16487000	USD
CY2018Q4	ottr	Net Regulatory Assets Liability Noncurrent NetRegulatoryAssetsLiabilityNoncurrent	-91212000	USD
CY2018Q4	us-gaap	Net Regulatory Assets NetRegulatoryAssets	-74725000	USD
CY2019	ottr	Stock Issued During Period Shares For Cash Invested Under Dividend Reinvestment And Share Purchase Plan StockIssuedDuringPeriodSharesForCashInvestedUnderDividendReinvestmentAndSharePurchasePlan	23740
CY2019	ottr	Stock Issued During Period Shares Vesting Of Restricted Stock Units StockIssuedDuringPeriodSharesVestingOfRestrictedStockUnits	29100
CY2019	us-gaap	Stock Issued During Period Shares Restricted Stock Award Gross StockIssuedDuringPeriodSharesRestrictedStockAwardGross	15700
CY2019	ottr	Directors Deferred Compensation DirectorsDeferredCompensation	594
CY2019	ottr	Shares Withheld For Individual Income Tax Requirements SharesWithheldForIndividualIncomeTaxRequirements	55224
CY2019Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	40157591
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	39720847
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	39599944
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	39457261
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	147001
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	212043
CY2017	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	210784
CY2019	ottr	Incremental Common Shares Attributable To Dilutive Effect Of Underlying Shares Related To Nonvested Restricted Stock Units Granted To Employees IncrementalCommonSharesAttributableToDilutiveEffectOfUnderlyingSharesRelatedToNonvestedRestrictedStockUnitsGrantedToEmployees	65421
CY2018	ottr	Incremental Common Shares Attributable To Dilutive Effect Of Underlying Shares Related To Nonvested Restricted Stock Units Granted To Employees IncrementalCommonSharesAttributableToDilutiveEffectOfUnderlyingSharesRelatedToNonvestedRestrictedStockUnitsGrantedToEmployees	59980
CY2017	ottr	Incremental Common Shares Attributable To Dilutive Effect Of Underlying Shares Related To Nonvested Restricted Stock Units Granted To Employees IncrementalCommonSharesAttributableToDilutiveEffectOfUnderlyingSharesRelatedToNonvestedRestrictedStockUnitsGrantedToEmployees	56952
CY2019	ottr	Incremental Common Shares Attributable To Dilutive Effect Of Nonvested Restricted Shares IncrementalCommonSharesAttributableToDilutiveEffectOfNonvestedRestrictedShares	15377
CY2018	ottr	Incremental Common Shares Attributable To Dilutive Effect Of Nonvested Restricted Shares IncrementalCommonSharesAttributableToDilutiveEffectOfNonvestedRestrictedShares	17751
CY2017	ottr	Incremental Common Shares Attributable To Dilutive Effect Of Nonvested Restricted Shares IncrementalCommonSharesAttributableToDilutiveEffectOfNonvestedRestrictedShares	20380
CY2019	ottr	Incremental Common Shares Attributable To Sharebased Payment Arrangements Employee Stock Purchase Plans IncrementalCommonSharesAttributableToSharebasedPaymentArrangementsEmployeeStockPurchasePlans	3228
CY2018	ottr	Incremental Common Shares Attributable To Sharebased Payment Arrangements Employee Stock Purchase Plans IncrementalCommonSharesAttributableToSharebasedPaymentArrangementsEmployeeStockPurchasePlans	0
CY2017	ottr	Incremental Common Shares Attributable To Sharebased Payment Arrangements Employee Stock Purchase Plans IncrementalCommonSharesAttributableToSharebasedPaymentArrangementsEmployeeStockPurchasePlans	0
CY2019	ottr	Incremental Common Shares Attributable To Dilutive Effect Of Shares Expected To Be Issued Under Deferred Compensation Program For Directors IncrementalCommonSharesAttributableToDilutiveEffectOfSharesExpectedToBeIssuedUnderDeferredCompensationProgramForDirectors	1952
CY2018	ottr	Incremental Common Shares Attributable To Dilutive Effect Of Shares Expected To Be Issued Under Deferred Compensation Program For Directors IncrementalCommonSharesAttributableToDilutiveEffectOfSharesExpectedToBeIssuedUnderDeferredCompensationProgramForDirectors	2478
CY2017	ottr	Incremental Common Shares Attributable To Dilutive Effect Of Shares Expected To Be Issued Under Deferred Compensation Program For Directors IncrementalCommonSharesAttributableToDilutiveEffectOfSharesExpectedToBeIssuedUnderDeferredCompensationProgramForDirectors	2970
CY2019	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	232979
CY2018	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	292252
CY2017	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	291086
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	39953826
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	39892196
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	39748347
CY2019	ottr	Maximum Per Share Differences Between Basic And Diluted Earnings Per Share In Total Or From Continuing Or Discontinued Operations MaximumPerShareDifferencesBetweenBasicAndDilutedEarningsPerShareInTotalOrFromContinuingOrDiscontinuedOperations	0.016
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	3571000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	3087000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	5587000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	26316000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	3987000	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	21851000	USD
CY2019Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	4136000	USD
CY2019Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	18193000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	22329000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	22329000	USD
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P6Y
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.053	pure
CY2019Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	3500000	USD
CY2019	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P1Y10M24D
CY2019Q4	ottr	Operating Lease Rightofuse Asset Gross OperatingLeaseRightofuseAssetGross	25919000	USD
CY2019Q4	ottr	Operating Lease Rightofuse Asset Accumulated Amortization OperatingLeaseRightofuseAssetAccumulatedAmortization	4068000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	5212000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	4945000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	3914000	USD
CY2018Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	20369000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	6318000	USD
CY2019	ottr	Operating Lease Lease Modifications OperatingLeaseLeaseModifications	-116000	USD
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	5371000	USD
CY2019	ottr	Operating Lease Interest OperatingLeaseInterest	1129000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	22329000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	5371000	USD
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	1068000	USD
CY2019	ottr	Rightofuse Lease Cost RightofuseLeaseCost	6439000	USD
CY2018	us-gaap	Operating Lease Expense OperatingLeaseExpense	6273000	USD
CY2019	ottr	Land Easement Nonlease Payments Expense LandEasementNonleasePaymentsExpense	617000	USD
CY2018	ottr	Land Easement Nonlease Payments Expense LandEasementNonleasePaymentsExpense	605000	USD
CY2017	ottr	Land Easement Nonlease Payments Expense LandEasementNonleasePaymentsExpense	593000	USD
CY2019Q4	us-gaap	Line Of Credit Facility Maximum Borrowing Capacity LineOfCreditFacilityMaximumBorrowingCapacity	340000000	USD
CY2019Q4	us-gaap	Line Of Credit LineOfCredit	6000000	USD
CY2019Q4	ottr	Line Of Credit Facility Amount Restricted LineOfCreditFacilityAmountRestricted	15476000	USD
CY2019Q4	us-gaap	Line Of Credit Facility Remaining Borrowing Capacity LineOfCreditFacilityRemainingBorrowingCapacity	318524000	USD
CY2018Q4	us-gaap	Line Of Credit Facility Remaining Borrowing Capacity LineOfCreditFacilityRemainingBorrowingCapacity	281101000	USD
CY2019	us-gaap	Shortterm Debt Maximum Amount Outstanding During Period ShorttermDebtMaximumAmountOutstandingDuringPeriod	109200000	USD
CY2019	us-gaap	Shortterm Debt Average Outstanding Amount ShorttermDebtAverageOutstandingAmount	36200000	USD
CY2019Q4	us-gaap	Short Term Debt Weighted Average Interest Rate ShortTermDebtWeightedAverageInterestRate	0.032	pure
CY2019Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	6000000	USD
CY2019Q4	us-gaap	Long Term Debt LongTermDebt	692351000	USD
CY2019Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	183000	USD
CY2019Q4	us-gaap	Debt Instrument Unamortized Discount DebtInstrumentUnamortizedDiscount	2587000	USD
CY2019Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	689581000	USD
CY2019Q4	us-gaap	Debt Longterm And Shortterm Combined Amount DebtLongtermAndShorttermCombinedAmount	695764000	USD
CY2018Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	18599000	USD
CY2018Q4	us-gaap	Long Term Debt LongTermDebt	592523000	USD
CY2018Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	172000	USD
CY2018Q4	us-gaap	Debt Instrument Unamortized Discount DebtInstrumentUnamortizedDiscount	2349000	USD
CY2018Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	590002000	USD
CY2018Q4	us-gaap	Debt Longterm And Shortterm Combined Amount DebtLongtermAndShorttermCombinedAmount	608773000	USD
CY2019Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	183000	USD
CY2019Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	140168000	USD
CY2019Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	30000000	USD
CY2019Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	0	USD
CY2019Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	0	USD
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Next Twelve Months DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths	15908000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Two DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo	16477000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Three DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree	17116000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Four DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour	17768000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Five DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive	18374000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Five Fiscal Years Thereafter DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter	98994000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Employer Contributions Next Fiscal Year DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear	3300000	USD
CY2019Q4	us-gaap	Prescription Drug Subsidy Receipts Next Twelve Months PrescriptionDrugSubsidyReceiptsNextTwelveMonths	100000	USD
CY2019	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	5265000	USD
CY2018	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	4532000	USD
CY2017	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	4211000	USD
CY2019	us-gaap	Employee Stock Ownership Plan Esop Cash Contributions To Esop EmployeeStockOwnershipPlanESOPCashContributionsToESOP	374000	USD
CY2018	us-gaap	Employee Stock Ownership Plan Esop Cash Contributions To Esop EmployeeStockOwnershipPlanESOPCashContributionsToESOP	398000	USD
CY2017	us-gaap	Employee Stock Ownership Plan Esop Cash Contributions To Esop EmployeeStockOwnershipPlanESOPCashContributionsToESOP	612000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1753794000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1581098000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21	pure
CY2017	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.35	pure
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	21901000	USD
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	20356000	USD
CY2017	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	34893000	USD
CY2019	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	3561000	USD
CY2018	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	5210000	USD
CY2017	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	4368000	USD
CY2019	ottr	Income Tax Reconciliation Differences Reversing In Excess Of Federal Rates IncomeTaxReconciliationDifferencesReversingInExcessOfFederalRates	-3357000	USD
CY2018	ottr	Income Tax Reconciliation Differences Reversing In Excess Of Federal Rates IncomeTaxReconciliationDifferencesReversingInExcessOfFederalRates	-3432000	USD
CY2017	ottr	Income Tax Reconciliation Differences Reversing In Excess Of Federal Rates IncomeTaxReconciliationDifferencesReversingInExcessOfFederalRates	551000	USD
CY2019	ottr	Effective Income Tax Rate Reconciliation Permanent Differences Rd Tax Credits Unitary Tax And Other Adjustments Amount EffectiveIncomeTaxRateReconciliationPermanentDifferencesRdTaxCreditsUnitaryTaxAndOtherAdjustmentsAmount	1315000	USD
CY2018	ottr	Effective Income Tax Rate Reconciliation Permanent Differences Rd Tax Credits Unitary Tax And Other Adjustments Amount EffectiveIncomeTaxRateReconciliationPermanentDifferencesRdTaxCreditsUnitaryTaxAndOtherAdjustmentsAmount	1864000	USD
CY2017	ottr	Effective Income Tax Rate Reconciliation Permanent Differences Rd Tax Credits Unitary Tax And Other Adjustments Amount EffectiveIncomeTaxRateReconciliationPermanentDifferencesRdTaxCreditsUnitaryTaxAndOtherAdjustmentsAmount	1873000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Credits Other IncomeTaxReconciliationTaxCreditsOther	1033000	USD
CY2018	us-gaap	Income Tax Reconciliation Tax Credits Other IncomeTaxReconciliationTaxCreditsOther	1033000	USD
CY2017	us-gaap	Income Tax Reconciliation Tax Credits Other IncomeTaxReconciliationTaxCreditsOther	850000	USD
CY2019	ottr	Effective Income Tax Rate Reconciliation Corporate Owned Life Insurance Amount EffectiveIncomeTaxRateReconciliationCorporateOwnedLifeInsuranceAmount	-749000	USD
CY2018	ottr	Effective Income Tax Rate Reconciliation Corporate Owned Life Insurance Amount EffectiveIncomeTaxRateReconciliationCorporateOwnedLifeInsuranceAmount	-3000	USD
CY2017	ottr	Effective Income Tax Rate Reconciliation Corporate Owned Life Insurance Amount EffectiveIncomeTaxRateReconciliationCorporateOwnedLifeInsuranceAmount	-845000	USD
CY2019	ottr	Effective Income Tax Rate Reconciliation Deduction Equity Method Stock Awards EffectiveIncomeTaxRateReconciliationDeductionEquityMethodStockAwards	744000	USD
CY2018	ottr	Effective Income Tax Rate Reconciliation Deduction Equity Method Stock Awards EffectiveIncomeTaxRateReconciliationDeductionEquityMethodStockAwards	708000	USD
CY2017	ottr	Effective Income Tax Rate Reconciliation Deduction Equity Method Stock Awards EffectiveIncomeTaxRateReconciliationDeductionEquityMethodStockAwards	751000	USD
CY2019	ottr	Income Tax Reconciliation Allowance For Funds Used During Construction IncomeTaxReconciliationAllowanceForFundsUsedDuringConstruction	501000	USD
CY2018	ottr	Income Tax Reconciliation Allowance For Funds Used During Construction IncomeTaxReconciliationAllowanceForFundsUsedDuringConstruction	431000	USD
CY2017	ottr	Income Tax Reconciliation Allowance For Funds Used During Construction IncomeTaxReconciliationAllowanceForFundsUsedDuringConstruction	322000	USD
CY2019	us-gaap	Income Tax Rate Reconciliation Deductions Employee Stock Ownership Plan Dividends IncomeTaxRateReconciliationDeductionsEmployeeStockOwnershipPlanDividends	281000	USD
CY2018	us-gaap	Income Tax Rate Reconciliation Deductions Employee Stock Ownership Plan Dividends IncomeTaxRateReconciliationDeductionsEmployeeStockOwnershipPlanDividends	298000	USD
CY2017	us-gaap	Income Tax Rate Reconciliation Deductions Employee Stock Ownership Plan Dividends IncomeTaxRateReconciliationDeductionsEmployeeStockOwnershipPlanDividends	509000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Credits Investment IncomeTaxReconciliationTaxCreditsInvestment	41000	USD
CY2018	us-gaap	Income Tax Reconciliation Tax Credits Investment IncomeTaxReconciliationTaxCreditsInvestment	98000	USD
CY2017	us-gaap	Income Tax Reconciliation Tax Credits Investment IncomeTaxReconciliationTaxCreditsInvestment	164000	USD
CY2019	ottr	Income Tax Reconciliation Production Tax Credit IncomeTaxReconciliationProductionTaxCredit	-0	USD
CY2018	ottr	Income Tax Reconciliation Production Tax Credit IncomeTaxReconciliationProductionTaxCredit	3111000	USD
CY2017	ottr	Income Tax Reconciliation Production Tax Credit IncomeTaxReconciliationProductionTaxCredit	7527000	USD
CY2019	us-gaap	Income Tax Reconciliation Deductions Qualified Production Activities IncomeTaxReconciliationDeductionsQualifiedProductionActivities	-0	USD
CY2018	us-gaap	Income Tax Reconciliation Deductions Qualified Production Activities IncomeTaxReconciliationDeductionsQualifiedProductionActivities	-0	USD
CY2017	us-gaap	Income Tax Reconciliation Deductions Qualified Production Activities IncomeTaxReconciliationDeductionsQualifiedProductionActivities	1471000	USD
CY2019	us-gaap	Income Tax Expense Benefit Continuing Operations Adjustment Of Deferred Tax Asset Liability IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability	0	USD
CY2018	us-gaap	Income Tax Expense Benefit Continuing Operations Adjustment Of Deferred Tax Asset Liability IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability	0	USD
CY2017	us-gaap	Income Tax Expense Benefit Continuing Operations Adjustment Of Deferred Tax Asset Liability IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability	1756000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	17441000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14588000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	27256000	USD
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.167	pure
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.150	pure
CY2017	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.273	pure
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	5156000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	4960000	USD
CY2017	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	4434000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Credits Other IncomeTaxReconciliationTaxCreditsOther	1033000	USD
CY2018	us-gaap	Income Tax Reconciliation Tax Credits Other IncomeTaxReconciliationTaxCreditsOther	1033000	USD
CY2017	us-gaap	Income Tax Reconciliation Tax Credits Other IncomeTaxReconciliationTaxCreditsOther	850000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Credits Investment IncomeTaxReconciliationTaxCreditsInvestment	41000	USD
CY2018	us-gaap	Income Tax Reconciliation Tax Credits Investment IncomeTaxReconciliationTaxCreditsInvestment	98000	USD
CY2017	us-gaap	Income Tax Reconciliation Tax Credits Investment IncomeTaxReconciliationTaxCreditsInvestment	164000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	17441000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	1333000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	1395000	USD
CY2017	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	1128000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	8859000	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	8065000	USD
CY2017	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	25648000	USD
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	3167000	USD
CY2018	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	4410000	USD
CY2017	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	4587000	USD
CY2019	ottr	Income Tax Reconciliation Production Tax Credit IncomeTaxReconciliationProductionTaxCredit	-0	USD
CY2018	ottr	Income Tax Reconciliation Production Tax Credit IncomeTaxReconciliationProductionTaxCredit	3111000	USD
CY2017	ottr	Income Tax Reconciliation Production Tax Credit IncomeTaxReconciliationProductionTaxCredit	7527000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14588000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	27256000	USD
CY2019	ottr	Income Loss Before Income Tax IncomeLossBeforeIncomeTax	104288000	USD
CY2018	ottr	Income Loss Before Income Tax IncomeLossBeforeIncomeTax	96933000	USD
CY2017	ottr	Income Loss Before Income Tax IncomeLossBeforeIncomeTax	99695000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	36246000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	33967000	USD
CY2019Q4	ottr	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pension And Postretirement Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensionAndPostretirementBenefits	36206000	USD
CY2018Q4	ottr	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pension And Postretirement Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensionAndPostretirementBenefits	32664000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Regulatory Assets And Liabilities DeferredTaxAssetsRegulatoryAssetsAndLiabilities	35700000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Regulatory Assets And Liabilities DeferredTaxAssetsRegulatoryAssetsAndLiabilities	33228000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards Other DeferredTaxAssetsTaxCreditCarryforwardsOther	31611000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards Other DeferredTaxAssetsTaxCreditCarryforwardsOther	32570000	USD
CY2019Q4	ottr	Deferred Tax Assets Cost Of Removal DeferredTaxAssetsCostOfRemoval	25604000	USD
CY2018Q4	ottr	Deferred Tax Assets Cost Of Removal DeferredTaxAssetsCostOfRemoval	21787000	USD
CY2019Q4	ottr	Deferred Tax Assets Production Tax Credits DeferredTaxAssetsProductionTaxCredits	20017000	USD
CY2018Q4	ottr	Deferred Tax Assets Production Tax Credits DeferredTaxAssetsProductionTaxCredits	32101000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Property Plant And Equipment DeferredTaxAssetsPropertyPlantAndEquipment	6979000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Property Plant And Equipment DeferredTaxAssetsPropertyPlantAndEquipment	6842000	USD
CY2019Q4	ottr	Deferred Tax Assets Lease Liability DeferredTaxAssetsLeaseLiability	5733000	USD
CY2018Q4	ottr	Deferred Tax Assets Lease Liability DeferredTaxAssetsLeaseLiability	0	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Compensated Absences DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsCompensatedAbsences	1884000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Compensated Absences DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsCompensatedAbsences	1919000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	1860000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	2489000	USD
CY2019Q4	ottr	Deferred Tax Assets Investment Tax Credits DeferredTaxAssetsInvestmentTaxCredits	408000	USD
CY2018Q4	ottr	Deferred Tax Assets Investment Tax Credits DeferredTaxAssetsInvestmentTaxCredits	449000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	344000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	3218000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	800000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	600000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	201792000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	200634000	USD
CY2019Q4	ottr	Deferred Tax Liabilities Retirement Benefits Regulatory Asset DeferredTaxLiabilitiesRetirementBenefitsRegulatoryAsset	36206000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	268495000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	261396000	USD
CY2018Q4	ottr	Deferred Tax Liabilities Retirement Benefits Regulatory Asset DeferredTaxLiabilitiesRetirementBenefitsRegulatoryAsset	32664000	USD
CY2019Q4	ottr	Deferred Tax Liabilities Excess Tax Over Book Pension DeferredTaxLiabilitiesExcessTaxOverBookPension	17556000	USD
CY2018Q4	ottr	Deferred Tax Liabilities Excess Tax Over Book Pension DeferredTaxLiabilitiesExcessTaxOverBookPension	15145000	USD
CY2019Q4	ottr	Deferred Tax Liabilities Right Of Use Asset DeferredTaxLiabilitiesRightOfUseAsset	5705000	USD
CY2018Q4	ottr	Deferred Tax Liabilities Right Of Use Asset DeferredTaxLiabilitiesRightOfUseAsset	-0	USD
CY2019Q4	ottr	Deferred Tax Liabilities Tax Credits DeferredTaxLiabilitiesTaxCredits	3126000	USD
CY2018Q4	ottr	Deferred Tax Liabilities Tax Credits DeferredTaxLiabilitiesTaxCredits	4386000	USD
CY2019Q4	ottr	Deferred Tax Liabilities Operating Loss Carryforwards State And Local DeferredTaxLiabilitiesOperatingLossCarryforwardsStateAndLocal	385000	USD
CY2018Q4	ottr	Deferred Tax Liabilities Operating Loss Carryforwards State And Local DeferredTaxLiabilitiesOperatingLossCarryforwardsStateAndLocal	523000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	2260000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	7496000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	333733000	USD
CY2018Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	321610000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	131941000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	120976000	USD
CY2018	ottr	Increase Decrease In Percentage Of Production Tax Credits IncreaseDecreaseInPercentageOfProductionTaxCredits	-0.530	pure
CY2018	ottr	Wind Tax Credits Amortization Period WindTaxCreditsAmortizationPeriod	P25Y
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	1282000	USD
CY2017Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	684000	USD
CY2016Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	891000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	37000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	6000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	28000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	-0	USD
CY2018	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	-0	USD
CY2017	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	172000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	339000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	778000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	143000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	170000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	186000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	206000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	1488000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	1282000	USD
CY2017Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	684000	USD
CY2019	ottr	Period For Unrecognized Tax Benefits Not Expected Change PeriodForUnrecognizedTaxBenefitsNotExpectedChange	P12M
CY2019Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	0	USD
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CY2018Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	9117000	USD
CY2017Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	8719000	USD
CY2019	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	0	USD
CY2018	us-gaap	Asset Retirement Obligation Liabilities Incurred AssetRetirementObligationLiabilitiesIncurred	0	USD
CY2019	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	3099000	USD
CY2018	us-gaap	Asset Retirement Obligation Revision Of Estimate AssetRetirementObligationRevisionOfEstimate	0	USD
CY2019	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	440000	USD
CY2018	us-gaap	Asset Retirement Obligation Accretion Expense AssetRetirementObligationAccretionExpense	398000	USD
CY2019	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	0	USD
CY2018	us-gaap	Asset Retirement Obligation Liabilities Settled AssetRetirementObligationLiabilitiesSettled	0	USD
CY2019Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	12656000	USD
CY2018Q4	us-gaap	Asset Retirement Obligation AssetRetirementObligation	9117000	USD
CY2018Q4	us-gaap	Capitalized Costs Asset Retirement Costs CapitalizedCostsAssetRetirementCosts	2983000	USD
CY2017Q4	us-gaap	Capitalized Costs Asset Retirement Costs CapitalizedCostsAssetRetirementCosts	2983000	USD
CY2019	ottr	Capitalized Costs Asset Retirement Costs Liabilities Incurred CapitalizedCostsAssetRetirementCostsLiabilitiesIncurred	0	USD
CY2018	ottr	Capitalized Costs Asset Retirement Costs Liabilities Incurred CapitalizedCostsAssetRetirementCostsLiabilitiesIncurred	0	USD
CY2019	ottr	Capitalized Costs Asset Retirement Costs Revision Of Estimate CapitalizedCostsAssetRetirementCostsRevisionOfEstimate	3099000	USD
CY2018	ottr	Capitalized Costs Asset Retirement Costs Revision Of Estimate CapitalizedCostsAssetRetirementCostsRevisionOfEstimate	0	USD
CY2019	ottr	Capitalized Costs Asset Retirement Costs Liabilities Settled CapitalizedCostsAssetRetirementCostsLiabilitiesSettled	0	USD
CY2018	ottr	Capitalized Costs Asset Retirement Costs Liabilities Settled CapitalizedCostsAssetRetirementCostsLiabilitiesSettled	0	USD
CY2019Q4	us-gaap	Capitalized Costs Asset Retirement Costs CapitalizedCostsAssetRetirementCosts	6082000	USD
CY2018Q4	us-gaap	Capitalized Costs Asset Retirement Costs CapitalizedCostsAssetRetirementCosts	2983000	USD
CY2018Q4	ottr	Capitalized Costs Asset Retirement Costs Accumulated Depreciation CapitalizedCostsAssetRetirementCostsAccumulatedDepreciation	1034000	USD
CY2017Q4	ottr	Capitalized Costs Asset Retirement Costs Accumulated Depreciation CapitalizedCostsAssetRetirementCostsAccumulatedDepreciation	915000	USD
CY2019	ottr	Capitalized Costs Asset Retirement Costs Accumulated Depreciation Liabilities Incurred CapitalizedCostsAssetRetirementCostsAccumulatedDepreciationLiabilitiesIncurred	0	USD
CY2018	ottr	Capitalized Costs Asset Retirement Costs Accumulated Depreciation Liabilities Incurred CapitalizedCostsAssetRetirementCostsAccumulatedDepreciationLiabilitiesIncurred	0	USD
CY2019	ottr	Capitalized Costs Asset Retirement Costs Accumulated Depreciation Revision Of Estimate CapitalizedCostsAssetRetirementCostsAccumulatedDepreciationRevisionOfEstimate	0	USD
CY2018	ottr	Capitalized Costs Asset Retirement Costs Accumulated Depreciation Revision Of Estimate CapitalizedCostsAssetRetirementCostsAccumulatedDepreciationRevisionOfEstimate	0	USD
CY2019	ottr	Capitalized Costs Asset Retirement Costs Accumulated Depreciation Depreciation Expense CapitalizedCostsAssetRetirementCostsAccumulatedDepreciationDepreciationExpense	163000	USD
CY2018	ottr	Capitalized Costs Asset Retirement Costs Accumulated Depreciation Depreciation Expense CapitalizedCostsAssetRetirementCostsAccumulatedDepreciationDepreciationExpense	119000	USD
CY2019	ottr	Capitalized Costs Asset Retirement Costs Accumulated Depreciation Liabilities Settled CapitalizedCostsAssetRetirementCostsAccumulatedDepreciationLiabilitiesSettled	0	USD
CY2018	ottr	Capitalized Costs Asset Retirement Costs Accumulated Depreciation Liabilities Settled CapitalizedCostsAssetRetirementCostsAccumulatedDepreciationLiabilitiesSettled	0	USD
CY2019Q4	ottr	Capitalized Costs Asset Retirement Costs Accumulated Depreciation CapitalizedCostsAssetRetirementCostsAccumulatedDepreciation	1197000	USD
CY2018Q4	ottr	Capitalized Costs Asset Retirement Costs Accumulated Depreciation CapitalizedCostsAssetRetirementCostsAccumulatedDepreciation	1034000	USD
CY2019	ottr	Asset Retirement Obligation Settlements Retired Original Capitalized Asset Retirement Cost AssetRetirementObligationSettlementsRetiredOriginalCapitalizedAssetRetirementCost	0	USD
CY2018	ottr	Asset Retirement Obligation Settlements Retired Original Capitalized Asset Retirement Cost AssetRetirementObligationSettlementsRetiredOriginalCapitalizedAssetRetirementCost	0	USD
CY2019	ottr	Asset Retirement Obligation Settlements Accumulated Depreciation AssetRetirementObligationSettlementsAccumulatedDepreciation	0	USD
CY2018	ottr	Asset Retirement Obligation Settlements Accumulated Depreciation AssetRetirementObligationSettlementsAccumulatedDepreciation	0	USD
CY2019	ottr	Asset Retirement Obligation Settlements Asset Retirement Obligation AssetRetirementObligationSettlementsAssetRetirementObligation	0	USD
CY2018	ottr	Asset Retirement Obligation Settlements Asset Retirement Obligation AssetRetirementObligationSettlementsAssetRetirementObligation	0	USD
CY2019	ottr	Asset Retirement Obligation Settlements Settlement Cost AssetRetirementObligationSettlementsSettlementCost	0	USD
CY2018	ottr	Asset Retirement Obligation Settlements Settlement Cost AssetRetirementObligationSettlementsSettlementCost	0	USD
CY2019	ottr	Asset Retirement Obligation Gain On Settlement AssetRetirementObligationGainOnSettlement	0	USD
CY2018	ottr	Asset Retirement Obligation Gain On Settlement AssetRetirementObligationGainOnSettlement	0	USD
CY2019Q4	us-gaap	Accounts Receivable Related Parties Current AccountsReceivableRelatedPartiesCurrent	2144000	USD
CY2019Q4	us-gaap	Interest Receivable Current InterestReceivableCurrent	117000	USD
CY2019Q4	us-gaap	Notes Receivable Related Parties Current NotesReceivableRelatedPartiesCurrent	0	USD
CY2019Q4	us-gaap	Notes Receivable Related Parties Noncurrent NotesReceivableRelatedPartiesNoncurrent	79251000	USD
CY2019Q4	us-gaap	Accounts Payable Related Parties Current AccountsPayableRelatedPartiesCurrent	7000	USD
CY2019Q4	us-gaap	Notes Payable Related Parties Classified Current NotesPayableRelatedPartiesClassifiedCurrent	89611000	USD
CY2018Q4	us-gaap	Accounts Receivable Related Parties Current AccountsReceivableRelatedPartiesCurrent	1931000	USD
CY2018Q4	us-gaap	Interest Receivable Current InterestReceivableCurrent	117000	USD
CY2018Q4	us-gaap	Notes Receivable Related Parties Current NotesReceivableRelatedPartiesCurrent	1167000	USD
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CY2018Q4	us-gaap	Accounts Payable Related Parties Current AccountsPayableRelatedPartiesCurrent	7000	USD
CY2018Q4	us-gaap	Notes Payable Related Parties Classified Current NotesPayableRelatedPartiesClassifiedCurrent	60626000	USD
CY2019	us-gaap	Cash Dividends Paid To Parent Company CashDividendsPaidToParentCompany	55660000	USD
CY2018	us-gaap	Cash Dividends Paid To Parent Company CashDividendsPaidToParentCompany	53134000	USD
CY2017	us-gaap	Cash Dividends Paid To Parent Company CashDividendsPaidToParentCompany	50571000	USD

Files In Submission

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2018 Q4 Form 10-K Financial Statement

#000143774920003157 Filed on February 20, 2020

Income Statement

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$OTTR Otter Tail Corp Stock $ottr

2018 Q4 Form 10-K Financial Statement

#000143774920003157 Filed on February 20, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

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Otter Tail Corp Stock $ottr