Debt (Summary of Additional Information of Credit facilities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revolving Secured Line of Credit [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	$ 163.5	$ 179.0	$ 204.7	$ 195.1
Average outstanding balance	101.2	70.5	102.2	94.4
Warehouse Facility II [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	290.2	169.1	290.2	169.1
Average outstanding balance	152.9	136.0	89.6	91.5
Warehouse Facility IV [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	26.7	0	26.7	39.6
Average outstanding balance	24.5	0	21.7	15.7
Warehouse Facility V [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	58.8	46.9	75.0	60.0
Average outstanding balance	$ 2.5	$ 42.0	$ 7.4	$ 27.5