Fair Values of Assets and Liabilities - Changes in Fair Value for All Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Fair Value Disclosures [Abstract]
Net gains and losses on available for sale securities included in securities gains (losses)	$ (7)	$ (9)
Net gains and losses on available for sale securities included in interest income	(1)	14
Net gains and losses on net derivative assets and liabilities included in mortgage banking revenue	150	353
Net gains and losses on net derivative assets and liabilities included in noninterest income	(3)	(22)
Net change in net derivative assets and liabilities in unrealized gains (losses) included in noninterest income	(88)	(103)
Net change in net derivative assets and liabilities in unrealized gains (losses) included in mortgage banking revenue	$ (250)	$ (358)