Bank Premises & Equipment (Bank Premises and Equipment) (Parenthetical) (Detail) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Bank Premises and Equipment
Land and improvements	[1]	$ 649	$ 663
Branches and undeveloped parcels of land
Bank Premises and Equipment
Land and improvements		$ 92	$ 92

[1] (a ) At both March 31, 2017 and December 31, 2016 , land and improvements , buildings and construction in progress i ncluded $ 92 associated w ith parcels of undeveloped land intended for future branch expansion.