Mortgage Servicing Rights - Changes in Fair Value of Capitalized MSRs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Transfers And Servicing Of Financial Assets [Abstract]
Balance at beginning of period	$ 2,618	$ 1,955	$ 2,680	$ 1,700
Rights purchased	1	3	2	5
Rights capitalized	71	233	155	487
Rights sold	(141)		(141)
Changes in fair value of MSRs
Due to fluctuations in market interest rates	(82)	305	(158)	432
Due to revised assumptions or models	44	(3)	56	(9)
Other changes in fair value	(99)	(116)	(182)	(238)
Balance at end of period	$ 2,412	$ 2,377	$ 2,412	$ 2,377