Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Nonrecurring Fair Value Inputs (Details)

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Fair Value Measurements - Nonrecurring Fair Value Inputs (Details) - USD ($)
$ in Millions
6 Months Ended 12 Months Ended
Jun. 30, 2015
Dec. 31, 2014
Instruments backed by residential real estate assets    
Fair Value Inputs [Abstract]    
Frequency of appraisals conducted 90 days  
Nonrecurring | Level 3 | Market Comparables | Minimum    
Fair Value Inputs [Abstract]    
Discount rate 14.00% 0.00%
Cost to sell 7.00% 7.00%
Nonrecurring | Level 3 | Market Comparables | Maximum    
Fair Value Inputs [Abstract]    
Discount rate 26.00% 28.00%
Cost to sell 16.00% 14.00%
Nonrecurring | Level 3 | Instruments backed by residential real estate assets    
Fair Value Inputs, Assets, Quantitative Information [Line Items]    
Assets, fair value $ 2,076 $ 4,636
Nonrecurring | Level 3 | Instruments backed by residential real estate assets | Market Comparables | Weighted Average    
Fair Value Inputs [Abstract]    
Discount rate 18.00% 8.00%
Cost to sell 7.00% 8.00%
Nonrecurring | Level 3 | Instruments backed by residential real estate assets | Loans and leases    
Fair Value Inputs, Assets, Quantitative Information [Line Items]    
Assets, fair value $ 2,076 $ 4,636