Derivative and Hedging Instruments (Schedule of Terms of Interest Rate Cap Agreements) - USD ($) $ in Millions		Mar. 31, 2021		Dec. 31, 2020
Derivative [Line Items]
Interest rate caps, fair value of less than $0.1 million		$ 0.2		$ 0.1
Warehouse Facility II [Member]
Derivative [Line Items]
Debt facility financing amount	[1],[2]	400.0
Warehouse Facility II [Member] | 5.50% Cap Interest Rate [Member]
Derivative [Line Items]
Debt facility financing amount		400.0		400.0
Notional Amount		$ 205.0		$ 205.0
Cap Interest Rate	[3]	5.50%		5.50%
Warehouse Facility IV [Member]
Derivative [Line Items]
Debt facility financing amount		$ 300.0	[1],[2]	$ 300.0
Notional Amount		300.0		300.0
Warehouse Facility IV [Member] | 5.50% Cap Interest Rate [Member]
Derivative [Line Items]
Notional Amount				$ 33.3
Cap Interest Rate	[3]			6.50%
Warehouse Facility IV [Member] | 6.50% Cap Interest Rate [Member]
Derivative [Line Items]
Notional Amount		$ 8.3		$ 50.0
Cap Interest Rate	[3]	6.50%		6.50%
Warehouse Facility IV [Member] | 6.50% Cap Interest Rate Additional [Member]
Derivative [Line Items]
Notional Amount		$ 12.5		$ 216.7
Cap Interest Rate	[3]	6.50%		6.50%
Warehouse Facility IV [Member] | 6.50% Cap Interest Rate Second Additional [Member]
Derivative [Line Items]
Notional Amount		$ 279.2
Cap Interest Rate	[3]	6.50%
Warehouse Facility V [Member]
Derivative [Line Items]
Debt facility financing amount	[1],[2]	$ 125.0
Warehouse Facility V [Member] | 6.50% Cap Interest Rate [Member]
Derivative [Line Items]
Debt facility financing amount		125.0		$ 125.0
Notional Amount		$ 94.0		$ 94.0
Cap Interest Rate	[3]	5.50%		5.50%
Warehouse Facility VII [Member]
Derivative [Line Items]
Debt facility financing amount	[1],[2]	$ 150.0
Notional Amount		150.0		$ 150.0
Warehouse Facility VII [Member] | 5.50% Cap Interest Rate [Member]
Derivative [Line Items]
Debt facility financing amount		150.0
Notional Amount		$ 50.0
Cap Interest Rate	[3]	5.50%
Warehouse Facility VII [Member] | 5.50% Cap Interest Rate Additional [Member]
Derivative [Line Items]
Notional Amount		$ 100.0		$ 81.3
Cap Interest Rate		5.50%	[3]	5.50%
Warehouse Facility VII [Member] | 5.00% Cap Interest Rate [Member]
Derivative [Line Items]
Debt facility financing amount				$ 150.0
Notional Amount				$ 68.7
Cap Interest Rate	[3]			5.50%
Warehouse Facility VIII [Member]
Derivative [Line Items]
Debt facility financing amount	[1],[2]	$ 200.0
Warehouse Facility VIII [Member] | 5.50% Cap Interest Rate [Member]
Derivative [Line Items]
Debt facility financing amount		200.0		$ 200.0
Notional Amount		$ 200.0		$ 200.0
Cap Interest Rate	[3]	5.50%		5.50%
Term ABS 2021-1 [Member]
Derivative [Line Items]
Debt facility financing amount		$ 100.0
Term ABS 2021-1 [Member] | 5.50% Cap Interest Rate [Member]
Derivative [Line Items]
Debt facility financing amount		100.0
Notional Amount		$ 100.0
Cap Interest Rate		5.50%

[1] Financing made available only to a specified subsidiary of the Company.

[2] Interest rate cap agreements are in place to limit the exposure to increasing interest rates

[3] Rate excludes the spread over the corresponding LIBOR or commercial paper rate.