Debt (Schedule of Additional Information Related to Debt Instruments) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Revolving Secured Line of Credit [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	$ 240.8	$ 216.0
Average outstanding balance	45.4	68.9
Warehouse Facility II [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	201.0	201.0
Average outstanding balance	8.9	42.8
Warehouse Facility IV [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	0.0	0.0
Average outstanding balance	0.0	0.0
Warehouse Facility V [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	0.0	0.0
Average outstanding balance	0.0	0.0
Warehouse Facility VI [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	0.0	0.0
Average outstanding balance	0.0	0.0
Warehouse Facility VIII [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	0.0	0.0
Average outstanding balance	$ 0.0	$ 0.0