Nonperforming Assets (Additional Information) (Detail) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Other Real Estate	[1]	$ 53	$ 54
Accrual Loans [Member]
Mortgage Loans in Process of Foreclosure, Amount		107	110
Proceeds due from FHA or VA [Member]
Mortgage Loans in Process of Foreclosure, Amount		99	103
Other Real Estate		50	50
Nonaccrual loans [Member]
Mortgage Loans in Process of Foreclosure, Amount		86	93
Residential Portfolio Segment [Member]
Other Real Estate		49	50
Commercial Portfolio Segment [Member]
Other Real Estate		2	2
Land and Land Improvements [Member]
Other Real Estate		$ 2	$ 2

[1] Does not include foreclosed real estate related to loans insured by the FHA or guaranteed by the VA. Proceeds due from the FHA and the VA are recorded as a receivable in Other assets in the Consolidated Balance Sheets until the property is conveyed and the funds are received. The receivable related to proceeds due from the FHA and the VA totaled $50 million at both March 31, 2019 and December 31, 2018.