Fair Value (Fair Value Measurements - Nonrecurring Fair Value Inputs) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans held-for-sale, net	$ 1,438	$ 2,003
Consumer Loans Auto Financing Receivable [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Prepayment Rate	1.30%
Minimum [Member] | Consumer Loans Auto Financing Receivable [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Loss Severity	0.00%
Fair Value Inputs, Discount Rate	0.00%
Maximum [Member] | Consumer Loans Auto Financing Receivable [Member] | Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Loss Severity	4.50%
Fair Value Inputs, Discount Rate	6.70%
Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans held-for-sale, net	$ 1,446	$ 1,554
Fair Value, Measurements, Nonrecurring [Member] | Consumer Loans Auto Financing Receivable [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans held-for-sale, net	1,356
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Consumer Loans Auto Financing Receivable [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans held-for-sale, net	$ 1,356