Debt (Schedule of Principal Debt Outstanding) (Details) - USD ($)		Oct. 27, 2016	[1]	Sep. 30, 2016		Dec. 31, 2015
Debt Instrument [Line Items]
Debt facility financing amount		$ 350,000,000		$ 2,528,200,000		$ 2,086,300,000
Deferred Debt Issuance Costs				(16,200,000)		(16,800,000)
Unamortized debt discount				(1,600,000)		(1,700,000)
Carrying Amount				2,510,400,000		2,067,800,000
Revolving Secured Line of Credit [Member]
Debt Instrument [Line Items]
Debt facility financing amount	[2]			85,200,000		57,700,000
Deferred Debt Issuance Costs	[2]			0		0
Unamortized debt discount	[2]			0		0
Carrying Amount	[2]			85,200,000		57,700,000
Secured financings [Member]
Debt Instrument [Line Items]
Debt facility financing amount				1,893,000,000	[2]	1,478,600,000	[3],[4]
Deferred Debt Issuance Costs				(8,800,000)	[2]	(8,500,000)	[3],[4]
Unamortized debt discount				0	[2]	0	[3],[4]
Carrying Amount				1,884,200,000	[2]	1,470,100,000	[3],[4]
Senior Notes [Member]
Debt Instrument [Line Items]
Debt facility financing amount				550,000,000		550,000,000	[3]
Deferred Debt Issuance Costs				(7,400,000)		(8,300,000)	[3]
Unamortized debt discount				(1,600,000)		(1,700,000)	[3]
Carrying Amount				$ 541,000,000		$ 540,000,000	[3]

[1] Financing made available only to a specified subsidiary of the Company.

[2] Excludes deferred debt issuance costs of $2.6 million and $2.2 million as of September 30, 2016 and December 31, 2015, respectively, which are included in other assets.

[3] 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.

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