Loans - Additional Information (Detail) (USD $)	33 Months Ended			3 Months Ended		9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Sep. 30, 2014 Consumer Loans [Member]	Sep. 30, 2013 Consumer Loans [Member]	Sep. 30, 2014 Consumer Loans [Member]	Sep. 30, 2013 Consumer Loans [Member]	Dec. 31, 2013 Consumer Loans [Member]	Sep. 30, 2014 Affiliated Entity [Member]	Dec. 31, 2013 Affiliated Entity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 73,439,000,000	$ 67,695,000,000	$ 67,710,000,000	$ 19,377,000,000		$ 19,377,000,000		$ 19,201,000,000	$ 4,812,000,000	$ 5,328,000,000
Net deferred origination fees	14,000,000	23,000,000
Net unamortized premium on loans	13,000,000	16,000,000
Commercial loans removed from TDR classification	$ 0
Weighted average rate of reduction				1.64%	1.76%	1.55%	1.97%