Fair Value (Fair Value Measurement - Nonrecurring Basis) (Details) (Fair Value, Measurements, Nonrecurring [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Held-for-sale, Other	$ 19
Commercial Finance Receivables and Loans, Net, Fair Value	158	198
Assets, Fair Value Disclosure	186	205
Lower of cost or fair value or valuation reserve allowance	0
Commercial Finance Receivables And Loans, Automotive [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	95	172
Lower of cost or fair value or valuation reserve allowance	(17)	(31)
Commercial Finance Receivables And Loans, Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	63	26
Lower of cost or fair value or valuation reserve allowance	(11)	(7)
Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Lower of cost or fair value or valuation reserve allowance	(28)	(38)
Repossessed And Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	7	7
Lower of cost or fair value or valuation reserve allowance	(2)	(1)
Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	2
Lower of cost or fair value or valuation reserve allowance	0
Assets, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Lower of cost or fair value or valuation reserve allowance	(30)	(39)
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Held-for-sale, Other	0
Commercial Finance Receivables and Loans, Net, Fair Value	0	0
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Commercial Finance Receivables And Loans, Automotive [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	0	0
Fair Value, Inputs, Level 1 [Member] | Commercial Finance Receivables And Loans, Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	0	0
Fair Value, Inputs, Level 1 [Member] | Repossessed And Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Held-for-sale, Other	0
Commercial Finance Receivables and Loans, Net, Fair Value	0	0
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Commercial Finance Receivables And Loans, Automotive [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	0	0
Fair Value, Inputs, Level 2 [Member] | Commercial Finance Receivables And Loans, Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	0	0
Fair Value, Inputs, Level 2 [Member] | Repossessed And Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Held-for-sale, Other	19
Commercial Finance Receivables and Loans, Net, Fair Value	158	198
Assets, Fair Value Disclosure	186	205
Fair Value, Inputs, Level 3 [Member] | Commercial Finance Receivables And Loans, Automotive [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	95	172
Fair Value, Inputs, Level 3 [Member] | Commercial Finance Receivables And Loans, Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	63	26
Fair Value, Inputs, Level 3 [Member] | Repossessed And Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	7	7
Fair Value, Inputs, Level 3 [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	$ 2