Variable Interest Entities - Activity of Alternative Energy Partnership Investments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Tax benefit (expense) recognized from HLBV application	$ (124.8)	$ 100.2	$ 130.5
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Fundings	80.0	20.0
Cash distribution from investment	0.5	0.0
Gain (loss) on investments in Alternative Energy Partnership	(61.2)	0.0
Income tax credits recognized	73.9	3.6
Tax benefit (expense) recognized from HLBV application	$ 5.1	$ (0.4)