Variable Interest Entities (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Income Tax Expense (Benefit)	$ (54,500,000)	$ 29,800,000	$ (83,200,000)	$ 77,100,000
Other Assets	619,300,000		619,300,000		$ 575,900,000
Variable Interest Entity, Not Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Variable Interest Entity, Funding Investment Commitment, Funding	31,500,000	0	80,000,000.0	0
Distribution of Accumulated Earnings of Equity Method Limited Liability Investments	200,000	0	200,000	0
Income (Loss) from Equity Method Investments	(23,800,000)	0	(46,900,000)	0
Income Tax Credits and Adjustments	28,700,000	0	64,800,000	0
Income Tax Expense (Benefit)	1,900,000	$ 0	3,000,000.0	$ 0
Cash and Cash Equivalents, at Carrying Value	17,200,000		17,200,000
Property, Plant and Equipment, Net	245,400,000		245,400,000
Other Assets	3,400,000		3,400,000
Assets	266,000,000.0		266,000,000.0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 54,200,000		$ 54,200,000