Loans Receivable (Summary of Changes In Allowance for Credit Losses) (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2019		Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period		$ 474.2		$ 448.4	$ 461.9	$ 429.4
Provision for credit losses		15.4		1.8	29.9	25.2
Transfers		0.0	[1]	0.0	0.0	0.0	[1]
Write-offs		(0.7)		(15.4)	(3.6)	(21.8)
Recoveries	[2],[3]	0.7		0.9	1.4	2.9
Balance, end of period		489.6		435.7	489.6	435.7
Dealer Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period		383.1		379.3	378.1	366.0
Provision for credit losses		14.5		3.2	26.1	21.9
Transfers		(3.3)	[1]	(2.7)	(7.5)	(5.6)	[1]
Write-offs		(0.6)		(14.5)	(3.4)	(18.8)
Recoveries	[2],[3]	0.3		0.6	0.7	2.4
Balance, end of period		394.0		365.9	394.0	365.9
Purchased Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period		91.1		69.1	83.8	63.4
Provision for credit losses		0.9		(1.4)	3.8	3.3
Transfers		3.3	[1]	2.7	7.5	5.6	[1]
Write-offs		(0.1)		(0.9)	(0.2)	(3.0)
Recoveries	[2],[3]	0.4		0.3	0.7	0.5
Balance, end of period		$ 95.6		$ 69.8	$ 95.6	$ 69.8

[1] 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 the related allowance for credit losses balance to Purchased Loans in the period this forfeiture occurs.

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

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