Fair Value Measurement - Nonrecurring Basis (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value option, changes in fair value gain (loss)	$ (114)	$ (318)	$ (183)	$ (456)
Residential mortgage | Broker Price Opinion Valuation Technique | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, liquidation value discount			23.00%
Residential mortgage | Broker Price Opinion Valuation Technique | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, liquidation value discount			8.00%
Residential mortgage | Broker Price Opinion Valuation Technique | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, liquidation value discount			59.00%
Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value, nonrecurring	2,000		$ 2,000		$ 3,400
Nonrecurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value, nonrecurring	94	597	94	597
Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value, nonrecurring	1,900	$ 2,800	1,900	$ 2,800
Nonrecurring | Level 3 | Consumer Loans Reclassified To Held-For-Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value, nonrecurring	1,300		1,300
Nonrecurring | Level 3 | Residential mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value, nonrecurring	$ 312		$ 312