Debt Debt (Schedule of Principal Debt Outstanding) (Details) - USD ($) $ in Millions		Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Debt Instrument, Principal Outstanding		$ 5,106.6	$ 4,616.5
Unamortized Debt Issuance Costs		(36.6)	(22.4)
Unamortized Discount		(2.5)	(3.4)
Debt Instrument, Carrying Amount		5,067.5	4,590.7
Revolving Secured Line Of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Principal Outstanding	[1]	79.2	30.9
Unamortized Debt Issuance Costs	[1]	0.0	0.0
Unamortized Discount		0.0	0.0
Debt Instrument, Carrying Amount	[1]	79.2	30.9
Secured financings [Member]
Debt Instrument [Line Items]
Debt Instrument, Principal Outstanding	[2]	4,019.0	3,776.7
Unamortized Debt Issuance Costs	[2]	(25.6)	(16.9)
Unamortized Discount		(2.5)	(3.4)
Debt Instrument, Carrying Amount	[2]	3,990.9	3,756.4
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Principal Outstanding		1,000.0	800.0
Unamortized Debt Issuance Costs		(11.0)	(5.5)
Unamortized Discount		0.0	0.0
Debt Instrument, Carrying Amount		989.0	794.5
Mortgage [Member]
Debt Instrument [Line Items]
Debt Instrument, Principal Outstanding		8.4	8.9
Unamortized Debt Issuance Costs		0.0	0.0
Unamortized Discount		0.0	0.0
Debt Instrument, Carrying Amount		8.4	8.9
Other Assets [Member]
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs	[2]	$ (4.2)	$ (3.9)

[1] Excludes deferred debt issuance costs of $4.2 million and $3.9 million as of December 31, 2023 and December 31, 2022, respectively, which are included in other assets.

[2] Warehouse facilities and Term ABS financings.