Debt Debt (Schedule of Principal Debt Outstanding) (Details) - USD ($) $ in Millions		Mar. 31, 2016		Dec. 31, 2015
Debt Instrument [Line Items]
Debt facility financing amount		$ 2,345.6		$ 2,086.3
Deferred Debt Issuance Costs		(15.6)		(16.8)
Unamortized debt discount		(1.7)		(1.7)
Carrying Amount		2,328.3		2,067.8
Revolving Secured Line of Credit [Member]
Debt Instrument [Line Items]
Debt facility financing amount	[1]	36.3		57.7
Deferred Debt Issuance Costs	[1]	0.0		0.0
Unamortized debt discount	[1]	0.0		0.0
Carrying Amount	[1]	36.3		57.7
Secured financings [Member]
Debt Instrument [Line Items]
Debt facility financing amount		1,759.3	[1]	1,478.6	[2],[3]
Deferred Debt Issuance Costs		(7.6)	[1]	(8.5)	[2],[3]
Unamortized debt discount		0.0	[1]	0.0	[2],[3]
Carrying Amount		1,751.7	[1]	1,470.1	[2],[3]
Senior Notes [Member]
Debt Instrument [Line Items]
Debt facility financing amount		550.0		550.0	[2]
Deferred Debt Issuance Costs		(8.0)		(8.3)	[2]
Unamortized debt discount		(1.7)		(1.7)	[2]
Carrying Amount		$ 540.3		$ 540.0	[2]

[1] Excludes deferred debt issuance costs of $2.0 million and $2.2 million as of March 31, 2016 and December 31, 2015, respectively, which are included in other assets.

[2] Prior year amounts have been reclassified to reflect the adoption of ASU 2015-03, as amended by ASU No. 2015-15, which resulted in a reclassification of certain deferred debt issuance costs from other assets to secured financing and senior notes.

[3] Warehouse facilities and asset-backed secured financings ("Term ABS").