Loans - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 69,588,000,000	$ 81,732,000,000	$ 73,875,000,000
Net deferred origination fees	39,000,000		48,000,000
Net unamortized premium (discount)	7,000,000		(5,000,000)
Commercial loans removed from TDR classification	0	$ 0
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 19,592,000,000		19,659,000,000
Weighted average rate of reduction	1.63%	2.29%
Loans which were classified as TDR loans during previous 12 months which became contractually delinquent	$ 3,000,000	$ 11,000,000
Affiliated Entity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 939,000,000	$ 5,107,000,000	$ 3,274,000,000