Loans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 82,917,000,000	$ 77,741,000,000	$ 67,695,000,000
Loans outstanding to executive officers and director as a percentage of shareholders' equity (does not exceed)	5.00%	5000000.00%
Net deferred origination fees	$ 62,000,000	$ 34,000,000
Net unamortized premium on loans	16,000,000	10,000,000
Commercial loans removed from TDR classification	0	0	$ 0
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 20,464,000,000	$ 19,654,000,000
Weighted average rate of reduction	1.74%	1.64%	1.94%
Affiliated Entity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 4,815,000,000	$ 4,821,000,000	$ 5,328,000,000