Derivative And Hedging Instruments (Schedule Of Terms Of Interest Rate Cap Agreements) (Details) - USD ($) $ in Millions		Dec. 31, 2017		Dec. 31, 2016
Derivative [Line Items]
Debt financing amount		$ 3,093.0		$ 2,622.1
Interest rate swap fair value		0.0		0.0
Warehouse Facility II [Member]
Derivative [Line Items]
Debt financing amount		400.0	[1],[2]	400.0
Warehouse Facility II [Member] | 5.50% Cap Interest Rate [Member]
Derivative [Line Items]
Notional value		$ 205.0		$ 325.0
Cap Interest Rate	[3]	5.50%		5.50%
Warehouse Facility IV [Member]
Derivative [Line Items]
Debt financing amount		$ 100.0	[1],[2]	$ 75.0
Notional value		100.0		75.0
Warehouse Facility IV [Member] | 5.50% Cap Interest Rate [Member]
Derivative [Line Items]
Notional value		$ 75.0
Cap Interest Rate	[3]	5.50%
Warehouse Facility IV [Member] | Original 5.50% Cap Interest Rate [Member]
Derivative [Line Items]
Notional value				$ 18.8
Cap Interest Rate	[3]			5.50%
Warehouse Facility IV [Member] | Additional 5.50% Cap Interest Rate [Member]
Derivative [Line Items]
Notional value				$ 56.2
Cap Interest Rate	[3]			5.50%
Warehouse Facility IV [Member] | 6.50% Cap Interest Rate [Member]
Derivative [Line Items]
Notional value		$ 25.0
Cap Interest Rate	[3]	6.50%
Warehouse Facility V [Member]
Derivative [Line Items]
Debt financing amount		$ 100.0	[1],[2]	$ 100.0
Warehouse Facility V [Member] | 5.50% Cap Interest Rate [Member]
Derivative [Line Items]
Notional value		$ 75.0		$ 75.0
Cap Interest Rate	[3]	5.50%		5.50%
Term ABS 2016-1 [Member]
Derivative [Line Items]
Debt financing amount		$ 385.0	[1]	$ 385.0
Term ABS 2016-1 [Member] | 5.00% Cap Interest Rate [Member]
Derivative [Line Items]
Notional value		$ 385.0		$ 385.0
Cap Interest Rate	[3]	5.00%		5.00%
Warehouse Facility VII [Member]
Derivative [Line Items]
Debt financing amount	[1],[2]	$ 150.0
Warehouse Facility VII [Member] | 5.50% Cap Interest Rate [Member]
Derivative [Line Items]
Notional value		$ 150.0
Cap Interest Rate	[3]	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 LIBOR rate.