Mortgage Servicing Rights - Changes in Fair Value of Capitalized MSRs (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Transfers and Servicing of Financial Assets [Abstract]
Balance at beginning of period	$ 2,222	$ 2,250	$ 2,512	$ 2,338
Rights purchased	5	9	14	15
Rights capitalized	131	164	230	309
Changes in fair value of MSRs
Due to fluctuations in market interest rates	(187)	172	(488)	41
Due to revised assumptions or models		2		2
Other changes in fair value	(115)	(116)	(212)	(224)
Balance at end of period	$ 2,056	$ 2,481	$ 2,056	$ 2,481