Fair Value Disclosure Fair Value Disclosure - Other Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 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	$ 5,280.9	$ 5,056.3
Recourse Floating Rate Debt Fair Value Disclosure	550.0	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	5,734.6	5,696.9
Recourse Floating Rate Debt Fair Value Disclosure	$ 550.4	$ 300.4