Debt Debt (Schedule of Principal Debt Outstanding) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 2,086.3	$ 1,752.5
Debt Instrument, Unamortized Discount		(1.7)	0.0
Debt Instrument, Carrying Amount		2,084.6	1,752.5
Revolving Secured Line Of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		57.7	119.5
Debt Instrument, Unamortized Discount		0.0	0.0
Debt Instrument, Carrying Amount		57.7	119.5
Secured financings [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[1]	1,478.6	1,333.0
Debt Instrument, Unamortized Discount	[1]	0.0	0.0
Debt Instrument, Carrying Amount	[1]	1,478.6	1,333.0
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		550.0	300.0
Debt Instrument, Unamortized Discount		(1.7)	0.0
Debt Instrument, Carrying Amount		$ 548.3	$ 300.0

[1] Warehouse facilities and Term ABS financings