Loans - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 77,625,000,000	$ 84,942,000,000	$ 77,625,000,000	$ 84,942,000,000	$ 82,917,000,000
Net deferred origination fees	54,000,000		54,000,000		62,000,000
Net unamortized premium on loans	2,000,000		2,000,000		16,000,000
Commercial loans removed from TDR classification	0	$ 0	0	$ 0
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 19,593,000,000		$ 19,593,000,000		20,464,000,000
Weighted average rate of reduction	1.41%	1.62%	1.61%	1.76%
Affiliated Entity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 4,463,000,000	$ 5,447,000,000	$ 4,463,000,000	$ 5,447,000,000	$ 4,815,000,000