Fair Value Disclosure Fair Value Disclosure - Other Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Recourse Fixed Rate Debt Fair Value Disclosure	$ 5,724.1	$ 5,056.3
Recourse Floating Rate Debt Fair Value Disclosure	683.9	299.9
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Recourse Fixed Rate Debt Fair Value Disclosure	6,111.4	5,696.9
Recourse Floating Rate Debt Fair Value Disclosure	$ 684.2	$ 300.4