Loans - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net deferred origination costs (fees)	$ 76,000,000		$ 77,000,000
Net unamortized premium (discount)	2,000,000		$ 11,000,000
Commercial loans removed from TDR classification	$ 0	$ 0