Fair Values of Assets and Liabilities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Fair value measurement transfers from one level to another			$ 0	$ 0
Mortgage loans held for sale measured at fair value gain losses	241	98	501	(38)
Assumed minimum credit valuation adjustment as percentage of underlying fair value of underlying derivative contracts			0.00%
Assumed maximum credit valuation adjustment as percentage of underlying fair value of underlying derivative contracts			97.00%
Assumed average credit valuation adjustment as percentage of underlying fair value of underlying derivative contracts			6.00%
Net gains and losses on available for sale securities included in securities gains (losses)	(15)	(9)	(37)	(24)
Net gains and losses on available for sale securities included in interest income	6	13	34	44
Net gains and losses on net derivative assets and liabilities included in mortgage banking revenue	719	391	1,700	580
Net gains and losses on net derivative assets and liabilities included in noninterest income	124	445	344	672
Net change in net derivative assets and liabilities in unrealized gains (losses) included in noninterest income	7	317	6	303
Net change in net derivative assets and liabilities in unrealized gains (losses) included in mortgage banking revenue	(564)	(240)	1,400	(395)
Carrying value of unfunded commitments and standby letters of credit	393		393		381
Carrying value of other guarantees	$ 423		$ 423		$ 359