Debt (Summary of Additional Information of Credit facilities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revolving Secured Line of Credit [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	$ 201.5	$ 195.1	$ 204.7	$ 195.1
Average outstanding balance	124.6	139.6	102.7	106.6
Warehouse Facility II [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	162.6	162.6	162.6	162.6
Average outstanding balance	56.5	48.0	57.5	68.9
Warehouse Facility III [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	69.1	60.0	75.0	60.0
Average outstanding balance	11.4	40.0	9.9	20.1
Warehouse Facility IV [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	26.5	37.6	26.6	39.6
Average outstanding balance	$ 24.5	$ 9.9	$ 20.2	$ 23.7