Accumulated Other Comprehensive Income (Loss) - Reconciliation of Transactions Affecting Accumulated Other Comprehensive Income (Loss) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance at beginning of period	$ (1,288)	$ (830)	$ (923)	$ (1,200)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Securities Available-For-Sale	(237)	300	(1,032)	738
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Derivative Hedges	(17)	(30)	33	(68)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Retirement Plans	38		37
Changes in unrealized gains and losses	(216)	270	(962)	670
Other-than-temporary impairment not recognized in earnings on securities available-for-sale	1	2	8	3
Foreign currency translation adjustment	13	26	(20)	34
Reclassification to earnings of realized gains and losses	99	69	270	260
Applicable income taxes	40	(140)	276	(370)
Balance at end of period	(1,351)	(603)	(1,351)	(603)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance at beginning of period	(60)	(44)	(40)	(49)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Securities Available-For-Sale
Other-than-temporary impairment not recognized in earnings on securities available-for-sale
Foreign currency translation adjustment	13	26	(20)	34
Reclassification to earnings of realized gains and losses
Applicable income taxes	(5)	(10)	8	(13)
Balance at end of period	(52)	(28)	(52)	(28)
Unrealized Gains (Losses) on Retirement Plans [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance at beginning of period	(1,184)	(977)	(1,265)	(1,022)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Retirement Plans	38		37
Other-than-temporary impairment not recognized in earnings on securities available-for-sale
Foreign currency translation adjustment
Reclassification to earnings of realized gains and losses	62	38	186	112
Applicable income taxes	(38)	(14)	(80)	(43)
Balance at end of period	(1,122)	(953)	(1,122)	(953)
Unrealized Gains (Losses) on Derivative Hedges [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance at beginning of period	(313)	(447)	(404)	(489)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Derivative Hedges	(17)	(30)	33	(68)
Other-than-temporary impairment not recognized in earnings on securities available-for-sale
Foreign currency translation adjustment
Reclassification to earnings of realized gains and losses	47	53	142	158
Applicable income taxes	(11)	(9)	(65)	(34)
Balance at end of period	(294)	(433)	(294)	(433)
Unrealized Gains (Losses) on Securities Transferred From Available For Sale to Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance at beginning of period	84	134	107
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Securities Available-For-Sale
Other-than-temporary impairment not recognized in earnings on securities available-for-sale
Transfer of securities from available-for-sale to held-to-maturity				224
Foreign currency translation adjustment
Reclassification to earnings of realized gains and losses	(13)	(21)	(50)	(28)
Applicable income taxes	5	8	19	(75)
Balance at end of period	76	121	76	121
Unrealized Gains (Losses) on Securities Available-For-Sale [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance at beginning of period	185	504	679	360
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Securities Available-For-Sale	(237)	300	(1,032)	738
Other-than-temporary impairment not recognized in earnings on securities available-for-sale	1	2	8	3
Transfer of securities from available-for-sale to held-to-maturity				(224)
Foreign currency translation adjustment
Reclassification to earnings of realized gains and losses	3	(1)	(8)	18
Applicable income taxes	89	(115)	394	(205)
Balance at end of period	$ 41	$ 690	$ 41	$ 690