Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Nonrecurring Fair Value Inputs (Details)

v3.8.0.1
Fair Value Measurements - Nonrecurring Fair Value Inputs (Details) - Nonrecurring - Level 3 - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Market Comparables | Minimum    
Fair Value Inputs [Abstract]    
OREO discount 13.00% 15.00%
Costs to sell 8.00% 5.00%
Market Comparables | Maximum    
Fair Value Inputs [Abstract]    
OREO discount 59.00% 58.00%
Costs to sell 26.00% 49.00%
Instruments backed by residential real estate assets    
Fair Value Inputs, Assets, Quantitative Information [Line Items]    
Assets, fair value $ 273 $ 894
Instruments backed by residential real estate assets | Market Comparables | Weighted Average    
Fair Value Inputs [Abstract]    
OREO discount 23.00% 23.00%
Costs to sell 9.00% 7.00%