Premises and Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Operating Leases, Rent Expense, Net	$ 201	$ 202	$ 200
Depreciation, Depletion and Amortization	175	179	175
Amortization Of Deferred Gain On Sale Lease Back Of Premises	17	43	$ 54
Sale Leaseback Transaction, Deferred Gain, Gross	$ 49	$ 67