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Income Taxes
 6 Months Ended
Jun. 30, 2022
Income Tax Disclosure [Abstract]  
Income Taxes Income TaxesThe reconciliation of the statutory federal income tax rate to our effective tax rate for each of the three and six months ended June 30, 2022 and 2021 is as follows:
Three Months Ended June 30,Six Months Ended June 30,
2022202120222021
Federal Statutory Rate21.0 %21.0 %21.0 %21.0 %
Increases (Decreases) in Tax from:
State Taxes on Income, Net of Federal Tax5.0 5.0 5.0 5.0 
Production Tax Credits (PTCs)(4.2)(6.3)(4.3)(6.8)
Amortization of Excess Deferred Income Taxes— (2.0)(0.5)(2.4)
North Dakota Wind Tax Credit Amortization, Net of Federal Tax(0.1)(0.3)(0.2)(0.3)
Corporate-Owned Life Insurance0.9 (1.0)0.6 (0.8)
Other, Net0.6 0.1 — 0.1 
Effective Tax Rate23.2 %16.5 %21.6 %15.8 %