Fair Value (Fair Value Measurement - Nonrecurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	$ 17	$ 0
Fair Value, Measurements, Nonrecurring [Member] | Loans held-for-sale, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	13		$ 15
Lower of cost or fair value or valuation reserve allowance	0		0
Fair Value, Measurements, Nonrecurring [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	45		43
Lower of cost or fair value or valuation reserve allowance	(6)		(6)
Fair Value, Measurements, Nonrecurring [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	34		46
Lower of cost or fair value or valuation reserve allowance	(25)		(18)
Fair Value, Measurements, Nonrecurring [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	79		89
Lower of cost or fair value or valuation reserve allowance	(31)		(24)
Fair Value, Measurements, Nonrecurring [Member] | Repossessed And Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	13		10
Lower of cost or fair value or valuation reserve allowance	(1)		(3)
Fair Value, Measurements, Nonrecurring [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	4		5
Lower of cost or fair value or valuation reserve allowance	0		0
Fair Value, Measurements, Nonrecurring [Member] | Assets, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	109		119
Lower of cost or fair value or valuation reserve allowance	(32)		(27)
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Loans held-for-sale, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0		0
Fair Value, Measurements, Nonrecurring [Member] | 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, Measurements, Nonrecurring [Member] | 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, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Loan [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, Measurements, Nonrecurring [Member] | 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, Measurements, Nonrecurring [Member] | 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		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Assets, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Loans held-for-sale, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0		0
Fair Value, Measurements, Nonrecurring [Member] | 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, Measurements, Nonrecurring [Member] | 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, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Loan [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, Measurements, Nonrecurring [Member] | 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, Measurements, Nonrecurring [Member] | 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		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Assets, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Loans held-for-sale, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	13		15
Fair Value, Measurements, Nonrecurring [Member] | 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	45		43
Fair Value, Measurements, Nonrecurring [Member] | 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	34		46
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	79		89
Fair Value, Measurements, Nonrecurring [Member] | 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	13		10
Fair Value, Measurements, Nonrecurring [Member] | 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	4		5
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Assets, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 109		$ 119