Loans Receivable (Schedule Of Consumer Loans Performance) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	$ 5,049.0	$ 4,207.0	$ 3,345.1	$ 2,719.8
Allowance for credit losses	(429.4)	(320.4)	(243.6)	(206.9)
Loans receivable, net	4,619.6	3,886.6
Loan Pool Performance Meets Or Exceeds Initial Estimates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	1,227.9	1,708.0
Allowance for credit losses	0.0	0.0
Loans receivable, net	1,227.9	1,708.0
Loan Pool Performance Less Than Initial Estimates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	3,821.1	2,499.0
Allowance for credit losses	(429.4)	(320.4)
Loans receivable, net	3,391.7	2,178.6
Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	3,518.1	3,209.0	2,823.4	2,389.8
Allowance for credit losses	(366.0)	(309.3)	(235.1)	(198.1)
Loans receivable, net	3,152.1	2,899.7
Dealer Loans [Member] \| Loan Pool Performance Meets Or Exceeds Initial Estimates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	755.2	1,002.2
Allowance for credit losses	0.0	0.0
Loans receivable, net	755.2	1,002.2
Dealer Loans [Member] \| Loan Pool Performance Less Than Initial Estimates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	2,762.9	2,206.8
Allowance for credit losses	(366.0)	(309.3)
Loans receivable, net	2,396.9	1,897.5
Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	1,530.9	998.0	521.7	330.0
Allowance for credit losses	(63.4)	(11.1)	$ (8.5)	$ (8.8)
Loans receivable, net	1,467.5	986.9
Purchased Loans [Member] \| Loan Pool Performance Meets Or Exceeds Initial Estimates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	472.7	705.8
Allowance for credit losses	0.0	0.0
Loans receivable, net	472.7	705.8
Purchased Loans [Member] \| Loan Pool Performance Less Than Initial Estimates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	1,058.2	292.2
Allowance for credit losses	(63.4)	(11.1)
Loans receivable, net	$ 994.8	$ 281.1

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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