Debt (Schedule of Additional Information Related to Debt Instruments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revolving Secured Line of Credit [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	$ 186.4	$ 206.3
Average outstanding balance	56.6	107.9
Warehouse Facility II [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	200.1	190.0
Average outstanding balance	4.4	27.7
Warehouse Facility IV [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	12.0	35.0
Average outstanding balance	12.0	6.4
Warehouse Facility V [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	40.0	75.0
Average outstanding balance	0.9	15.2
Warehouse Facility VI [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	14.7	0.0
Average outstanding balance	$ 8.9	$ 0.0