v3.10.0.1
Investment Securities (Gross Realized Gains and Losses on Sales of AFS Securities) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Available-for-sale Securities [Abstract]      
Gross realized gains $ 12 $ 46 $ 133
Gross realized (losses) (4) (11) (21)
Total $ 8 $ 35 $ 112