Mortgage Servicing Rights - Changes in Fair Value of Capitalized MSRs (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Transfers and Servicing of Financial Assets [Abstract]
Balance at beginning of period	$ 2,481	$ 2,412	$ 2,338	$ 2,680
Rights purchased	7	1	22	3
Rights capitalized	182	109	491	264
Rights sold				(141)
Changes in fair value of MSRs
Due to fluctuations in market interest rates	(168)	29	(127)	(129)
Due to revised assumptions or models	7	15	9	71
Other changes in fair value	(112)	(105)	(336)	(287)
Balance at end of period	$ 2,397	$ 2,461	$ 2,397	$ 2,461