Bank Premises and Equipment (Bank Premises and Equipment (Parenthetical) (Detail)) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment
Land and improvements	[1]	$ 644	$ 663
Branches and undeveloped parcels of land
Property, Plant and Equipment
Land and improvements		$ 91	$ 92

[1] (a) At December 31, 2017 and 2016 , land and improvements, buildings and construction in progress included $ 91 and $ 92 , respectively, associated with parcels of undeveloped land intended for future branch expansion.