Mortgage Servicing Rights - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Transfers And Servicing Of Financial Assets [Abstract]
Company serviced residential mortgage loan for others	$ 226,700,000,000		$ 226,700,000,000		$ 215,600,000,000
Gain/Loss on the fair value of mortgage servicing rights and fair value changes of derivatives used to offset MSR	108,000,000	10,000,000	163,000,000	72,000,000
Loan servicing fees	$ 192,000,000	$ 181,000,000	$ 566,000,000	$ 526,000,000