Loans Receivable (Summary Of Changes In Allowance For Credit Losses) (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Dec. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance, beginning of period			$ 429.4		$ 320.4		$ 243.6
Provision for credit losses			56.9		129.3		90.2
Transfers	[1]		0.0		0.0
Write-offs			(28.6)		(22.1)		(14.8)
Recoveries	[2]		4.2	[3]	1.8	[1]	1.4	[1]
Balance, end of period		$ 429.4	461.9		429.4		320.4
Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance, beginning of period			366.0		309.3		235.1
Provision for credit losses			48.0		103.4		87.3
Transfers	[1]	(31.8)	(13.7)		(31.8)
Write-offs			(25.2)		(16.4)		(14.4)
Recoveries	[2]		3.0	[3]	1.5	[3]	1.3	[1]
Balance, end of period		366.0	378.1		366.0		309.3
Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance, beginning of period			63.4		11.1		8.5
Provision for credit losses			8.9		25.9		2.9
Transfers	[1]		13.7		31.8
Write-offs			(3.4)		(5.7)		(0.4)
Recoveries	[2]		1.2	[3]	0.3	[1]	0.1	[1]
Balance, end of period		$ 63.4	$ 83.8		$ 63.4		$ 11.1

[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 to Purchased Loans in the period this forfeiture occurs. Beginning in the fourth quarter of 2017, we also transfer 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.