Loans Receivable (Summary Of Changes In Accretable Yield) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance, beginning of period		$ 1,330.7	$ 1,072.8	$ 861.7
New Consumer Loan assignments	[1]	1,180.9	1,067.3	882.1
Accretion	[2]	(1,020.2)	(883.3)	(739.9)
Provision for credit losses		129.3	90.2	41.5
Forecast changes		36.1	(20.1)	23.9
Transfers	[3]	8.7	3.8	3.5
Balance, end of period		1,665.5	1,330.7	1,072.8
Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance, beginning of period		982.6	874.2	725.2
New Consumer Loan assignments	[1]	803.0	782.6	743.7
Accretion	[2]	(766.6)	(723.8)	(637.2)
Provision for credit losses		103.4	87.3	41.8
Forecast changes		(5.6)	(35.4)	3.6
Transfers	[3]	(28.2)	(2.3)	(2.9)
Balance, end of period		1,088.6	982.6	874.2
Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance, beginning of period		348.1	198.6	136.5
New Consumer Loan assignments	[1]	377.9	284.7	138.4
Accretion	[2]	(253.6)	(159.5)	(102.7)
Provision for credit losses		25.9	2.9	(0.3)
Forecast changes		41.7	15.3	20.3
Transfers	[3]	36.9	6.1	6.4
Balance, end of period		$ 576.9	$ 348.1	$ 198.6

[1] The Dealer Loans amount represents the net cash flows expected at the time of assignment on Consumer Loans assigned under our Portfolio Program, less the related advances paid to Dealers. The Purchased Loans amount represents the net cash flows expected at the time of assignment on Consumer Loans assigned under our Purchase Program, less the related one-time payments made to Dealers.

[2] Represents finance charges excluding the amortization of deferred direct origination costs for Dealer Loans.

[3] Under our Portfolio Program, certain events may result in Dealers forfeiting their rights to Dealer Holdback. We transfer the Dealer’s outstanding Dealer Loan balance and related expected future net cash flows to Purchased Loans in the period this forfeiture occurs