Variable Interest Entities - Additional Disclosures (Details) $ in Millions	12 Months Ended		15 Months Ended
	Sep. 30, 2015 USD ($) VIE	Sep. 30, 2014 USD ($) transfer	Dec. 31, 2014 transfer VIE
Variable Interest Entity [Line Items]
Number of VIEs formed | VIE			3
Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entities, Income | $	$ 34.4	$ 16.2
Variable Interest Entities, Expense | $	$ 30.4	$ 7.4
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Number of VIEs | VIE	2
Grupo Finmart [Member]
Variable Interest Entity [Line Items]
Number of transfers of consumer loans to various securitization trusts | transfer		5	6
Grupo Finmart [Member] | VIE C and B [Member]
Variable Interest Entity [Line Items]
Percent of cash flows received	100.00%
Grupo Finmart [Member] | VIE A [Member]
Variable Interest Entity [Line Items]
Percent of cash flows received	50.00%