Debt Debt (Schedule of Principal Debt Outstanding) (Details) - USD ($) $ in Millions		Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Debt Instrument, Principal Outstanding		$ 4,642.7	$ 4,635.1
Unamortized Debt Issuance Costs		(26.4)	(26.5)
Debt Instrument, Carrying Amount		4,616.3	4,608.6
Revolving Secured Line Of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Principal Outstanding	[1]	2.6	95.9
Unamortized Debt Issuance Costs	[1]	0.0	0.0
Debt Instrument, Carrying Amount	[1]	2.6	95.9
Secured financings [Member]
Debt Instrument [Line Items]
Debt Instrument, Principal Outstanding	[2]	3,830.4	3,728.7
Unamortized Debt Issuance Costs	[2]	(18.9)	(17.1)
Debt Instrument, Carrying Amount	[2]	3,811.5	3,711.6
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Principal Outstanding		800.0	800.0
Unamortized Debt Issuance Costs		(7.5)	(9.4)
Debt Instrument, Carrying Amount		792.5	790.6
Mortgage [Member]
Debt Instrument [Line Items]
Debt Instrument, Principal Outstanding		9.7	10.5
Unamortized Debt Issuance Costs		0.0	0.0
Debt Instrument, Carrying Amount		9.7	10.5
Other Assets [Member]
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs	[2]	$ (3.6)	$ (3.2)

[1] Excludes deferred debt issuance costs of $3.6 million and $3.2 million as of December 31, 2021 and December 31, 2020, respectively, which are included in other assets.

[2] Warehouse facilities and Term ABS.