Loans Receivable (Schedule of Loans Receivable) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	$ 4,061.2	$ 3,812.0	$ 3,345.1	$ 3,189.7	$ 3,052.6	$ 2,719.8
Allowance for credit losses	(296.8)	(276.9)	(243.6)	(230.2)	(217.9)	(206.9)
Loans receivable, net	3,764.4		3,101.5
Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	3,151.9	3,049.2	2,823.4	2,726.5	2,634.8	2,389.8
Allowance for credit losses	(287.0)	(268.2)	(235.1)	(221.8)	(209.4)	(198.1)
Loans receivable, net	2,864.9		2,588.3
Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	909.3	762.8	521.7	463.2	417.8	330.0
Allowance for credit losses	(9.8)	$ (8.7)	(8.5)	$ (8.4)	$ (8.5)	$ (8.8)
Loans receivable, net	$ 899.5		$ 513.2

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section L
-Subsection 1

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

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