Loans Receivable (Summary of Changes In Allowance for Credit Losses) (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017		Jun. 30, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period		$ 338.0		$ 262.8		$ 320.4		$ 243.6
Provision for credit losses		21.8		17.9		42.3		40.0
Write-offs		(6.2)		(4.2)		(9.4)		(7.4)
Recoveries	[1],[2]	0.5		0.4		0.8		0.7
Balance, end of period		354.1		276.9		354.1		276.9
Dealer Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period		323.8		254.0		309.3		235.1
Provision for credit losses		18.2		17.9		35.4		39.7
Write-offs		(5.5)		(4.1)		(8.5)		(7.3)
Recoveries	[1],[2]	0.4		0.4		0.7		0.7
Balance, end of period		336.9		268.2		336.9		268.2
Purchased Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period		14.2		8.8		11.1		8.5
Provision for credit losses		3.6		0.0		6.9		0.3
Write-offs		(0.7)		(0.1)		(0.9)		(0.1)
Recoveries	[2]	0.1	[1]	0.0	[1]	0.1	[1]	0.0
Balance, end of period		$ 17.2		$ 8.7		$ 17.2		$ 8.7

[1] Represents collections received on previously written off Loans.

[2] Represents collections received on previously written off Loans.