Loans - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 81,732,000,000	$ 81,458,000,000	$ 82,917,000,000
Net deferred origination fees	59,000,000		62,000,000
Net unamortized premium on loans	18,000,000		16,000,000
Commercial loans removed from TDR classification	0	$ 0
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 20,120,000,000		20,464,000,000
Weighted average rate of reduction	2.29%	1.77%
Affiliated Entity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 5,107,000,000	$ 5,016,000,000	$ 4,815,000,000