Loans Receivable (Summary of Changes in Accretable Yield) (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015		Jun. 30, 2016		Jun. 30, 2015
Certain Loans Acquired in Transfer Not Accounted for as Loans Accretable Yield Movement Schedule [Roll Forward]
Balance, beginning of period		$ 1,185.2	$ 957.5		$ 1,072.8		$ 861.7
New Consumer Loan assignments	[1]	253.9	200.5		555.3		451.9
Accretion	[2]	(217.4)	(182.5)	[3]	(422.5)	[3]	(354.8)	[3]
Provision for credit losses		17.9	8.4		40.0	[3]	14.6	[3]
Forecast changes		6.5	8.5		(0.2)	[3]	17.9	[3]
Transfers	[4]	0.4	1.1		1.1		2.2
Balance, end of period		1,246.5	993.5		1,246.5		993.5
Dealer Loans [Member]
Certain Loans Acquired in Transfer Not Accounted for as Loans Accretable Yield Movement Schedule [Roll Forward]
Balance, beginning of period		946.6	802.4		874.2		725.2
New Consumer Loan assignments	[1]	183.6	170.1		417.7		386.7
Accretion	[2]	(180.4)	(157.7)	[3]	(354.1)	[3]	(307.1)	[3]
Provision for credit losses		17.9	8.6		39.7	[3]	14.8	[3]
Forecast changes		(3.9)	2.6		(13.5)	[3]	7.4	[3]
Transfers	[4]	(0.6)	(0.9)		(0.8)		(1.9)
Balance, end of period		963.2	825.1		963.2		825.1
Purchased Loans [Member]
Certain Loans Acquired in Transfer Not Accounted for as Loans Accretable Yield Movement Schedule [Roll Forward]
Balance, beginning of period		238.6	155.1		198.6		136.5
New Consumer Loan assignments	[1]	70.3	30.4		137.6		65.2
Accretion	[2]	(37.0)	(24.8)	[3]	(68.4)	[3]	(47.7)	[3]
Provision for credit losses		0.0	(0.2)		0.3	[3]	(0.2)	[3]
Forecast changes		10.4	5.9		13.3	[3]	10.5	[3]
Transfers	[4]	1.0	2.0		1.9		4.1
Balance, end of period		$ 283.3	$ 168.4		$ 283.3		$ 168.4

[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] We have changed the presentation from prior periods to: (i) exclude the amortization of deferred direct origination costs for Dealer Loans from accretion (finance charge income under our previous presentation) and forecast changes and (ii) present provision for credit losses and forecast changes as separate activities. Under our previous presentation, we presented: (i) finance charges as reported in our consolidated statements of income and (ii) provision for credit losses and forecast changes as a combined activity.

[4] 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.