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Variable Interest Entities (Narrative) (Details) $ in Thousands		3 Months Ended		12 Months Ended
	Mar. 18, 2024 USD ($)	Mar. 31, 2024 USD ($) Rate MW	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Variable Interest Entity [Line Items]
Wind Power Purchase Agreement, Purchase Percentage | Rate		100.00%
Payments to Acquire Assets, Investing Activities	$ 110,600
Business Acquisition, Transaction Costs				$ 54,700
Proceeds from Contributed Capital				2,160,000
Redeemable Noncontrolling Interest, Equity, Other, Carrying Amount				1,360,000
Income Taxes		$ 76,000	$ 85,800	$ 63,500
Rosewater
Variable Interest Entity [Line Items]
Nameplate Capacity | MW		102
Indiana Crossroads Wind
Variable Interest Entity [Line Items]
Nameplate Capacity | MW		302
Indiana Crossroads Solar
Variable Interest Entity [Line Items]
Nameplate Capacity | MW		465
Dunns Bridge I
Variable Interest Entity [Line Items]
Nameplate Capacity | MW		465

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