Discontinued Operations and Restructuring - Additional Disclosures (Details) $ in Millions	12 Months Ended			15 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($) asset_sale	Dec. 31, 2014 transfer
Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Intercompany liabilities		$ 19.7
Revenues	$ 2.1	124.7	$ 188.8
Grupo Finmart
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of transfers of consumer loans to various securitization trusts			5	6
Consolidated Variable Interest Entities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Variable interest entities, income	12.6	34.4
Variable interest entities, expense	$ 9.7	$ 30.4