Mortgage Servicing Rights - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Transfers and Servicing of Financial Assets [Abstract]
Residential mortgage loans serviced for others including subserviced mortgages with no corresponding MSRs asset	$ 225,200,000,000		$ 225,000,000,000
Gain/Loss on fair value changes of MSRs due to changes in valuation assumptions and derivatives used to economically hedge MSRs	(1,000,000)	58,000,000
Loan servicing fees	$ 178,000,000	$ 188,000,000