Bank Premises and Equipment (Bank Premises and Equipment (Parenthetical) (Detail)) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment
Land and improvements	[1]	$ 634	$ 639
Branches and undeveloped parcels of land
Property, Plant and Equipment
Land and improvements		$ 53	$ 51

[1] At March 31, 2020 and December 31, 2019, land and improvements, buildings and construction in progress included $53 and $51, respectively, associated with parcels of undeveloped land intended for future branch expansion.