Bank Premises and Equipment (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Land and improvements	[1]	$ 685	$ 793
Buildings		1,755	1,807
Equipment		1,696	1,682
Leasehold improvements		403	416
Construction in progress		85	98
Land and improvements held for sale		55	23
Buildings held for sale		20	3
Equipment held for sale		3
Leasehold improvements held for sale		3
Accumulated depreciation and amortization		(2,466)	(2,357)
Total bank premises and equipment	[2]	$ 2,239	$ 2,465
Building | Upper Limit
Property, Plant and Equipment [Line Items]
Useful life		30 years
Building | Lower limit
Property, Plant and Equipment [Line Items]
Useful life		2 years
Equipment | Upper Limit
Property, Plant and Equipment [Line Items]
Useful life		30 years
Equipment | Lower limit
Property, Plant and Equipment [Line Items]
Useful life		2 years
Leasehold Improvements | Upper Limit
Property, Plant and Equipment [Line Items]
Useful life		30 years
Leasehold Improvements | Lower limit
Property, Plant and Equipment [Line Items]
Useful life		5 years

[1] At December 31, 2015 and 2014, land and improvements included $102 and $165, respectively, associated with parcels of undeveloped land intended for future branch expansion.

[2] Includes $81 and $26 of bank premises and equipment held for sale at December 31, 2015 and 2014, respectively. For further information refer to Note 7.