XML 86 R73.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2
Securities - Realized gains and losses on investment securities Transactions Attributable to available-for-sale securities (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]      
Gross realized gains $ 148 $ 54 $ 65
Gross realized losses (60) (30) (13)
Net realized gains $ 88 $ 24 $ 52