Mortgage Servicing Rights - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Transfers and Servicing of Financial Assets [Abstract]
Residential mortgage loans serviced for others including subserviced mortgages with no corresponding MSRs asset	$ 231,900		$ 231,900		$ 231,800
Gain (Loss) on fair value changes of MSRs due to changes in valuation assumptions and derivatives used to economically hedge MSRs	(10)	$ 7	(32)	$ 6
Loan servicing and ancillary fees	$ 186	$ 179	$ 370	$ 357