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Income Taxes - Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal Statutory Rate	21.00%	21.00%	21.00%
Increases (Decreases) in Tax from:
State Taxes on Income, Net of Federal Tax	4.70%	4.00%	3.40%
Production Tax Credits (PTCs)	(5.90%)	(1.10%)	0.00%
Amortization of Excess Deferred Income Taxes	(2.00%)	(3.60%)	(3.20%)
North Dakota Wind Tax Credit Amortization, Net of Federal Tax	(0.30%)	(0.90%)	(1.00%)
Allowance for Equity Funds Used During Construction	(0.10%)	(0.70%)	(0.50%)
Other, Net	(0.50%)	(1.30%)	(3.00%)
Effective Tax Rate	16.90%	17.40%	16.70%

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Effective Income Tax Rate Reconciliation, Allowance for Equity, Funds Used During Construction, Percent

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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-Publisher FASB
-Name Accounting Standards Codification
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to statutory income tax expense (benefit) outside of the country of domicile.

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