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Income Taxes - Summary of Effective Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes at Federal Statutory Rate	$ 76,332	$ 75,082	$ 44,692
Increases (Decreases) in Tax from:
State Taxes on Income, Net of Federal Tax	14,429	15,049	9,962
Production Tax Credits (PTCs)	(17,394)	(14,985)	(12,503)
Amortization of Excess Deferred Income Taxes	(2,205)	(1,625)	(4,262)
North Dakota Wind Tax Credit Amortization, Net of Federal Tax	(586)	(586)	(586)
Other, Net	(1,278)	416	(1,251)
Income Tax Expense (Benefit)	$ 69,298	$ 73,351	$ 36,052
Increases (Decreases) in Tax from:
Income Taxes at Federal Statutory Rate	21.00%	21.00%	21.00%
State Taxes on Income, Net of Federal Tax	4.00%	4.20%	4.70%
Production Tax Credits (PTCs)	(4.80%)	(4.20%)	(5.90%)
Amortization of Excess Deferred Income Taxes	(0.60%)	(0.50%)	(2.00%)
North Dakota Wind Tax Credit Amortization, Net of Federal Tax	(0.20%)	(0.20%)	(0.30%)
Other, Net	(0.30%)	0.20%	(0.60%)
Income Taxes at Effective Tax Rate	19.10%	20.50%	16.90%

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