Accumulated Other Comprehensive Income (Loss) - Reconciliation of Transactions Affecting Accumulated Other Comprehensive Income (Loss) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance at beginning of period	$ (941)	$ (944)	$ (923)	$ (1,200)
Changes in unrealized gains and losses	(622)	92	(746)	400
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Securities Available-For-Sale	(675)	132	(795)	438
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Derivative Hedges	53	(40)	50	(38)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Retirement Plans			(1)
Other-than-temporary impairment not recognized in earnings on securities available-for-sale	1	1	7	1
Foreign currency translation adjustment	(23)	(6)	(33)	8
Reclassification to earnings of realized gains and losses	80	100	171	191
Applicable income taxes	217	(73)	236	(230)
Balance at end of period	(1,288)	(830)	(1,288)	(830)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance at beginning of period	(46)	(40)	(40)	(49)
Foreign currency translation adjustment	(23)	(6)	(33)	8
Applicable income taxes	9	2	13	(3)
Balance at end of period	(60)	(44)	(60)	(44)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance at beginning of period	(1,221)	(999)	(1,265)	(1,022)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Retirement Plans			(1)
Reclassification to earnings of realized gains and losses	62	36	124	74
Applicable income taxes	(25)	(14)	(42)	(29)
Balance at end of period	(1,184)	(977)	(1,184)	(977)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance at beginning of period	(371)	(455)	(404)	(489)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Derivative Hedges	53	(40)	50	(38)
Reclassification to earnings of realized gains and losses	41	52	95	105
Applicable income taxes	(36)	(4)	(54)	(25)
Balance at end of period	(313)	(447)	(313)	(447)
Accumulated Net Unrealized Gain Loss 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	94		107
Transfer of securities from available-for-sale to held-to-maturity		224		224
Reclassification to earnings of realized gains and losses	(17)	(7)	(37)	(7)
Applicable income taxes	7	(83)	14	(83)
Balance at end of period	84	134	84	134
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance at beginning of period	603	550	679	360
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Securities Available-For-Sale	(675)	132	(795)	438
Other-than-temporary impairment not recognized in earnings on securities available-for-sale	1	1	7	1
Transfer of securities from available-for-sale to held-to-maturity		(224)		(224)
Reclassification to earnings of realized gains and losses	(6)	19	(11)	19
Applicable income taxes	262	26	305	(90)
Balance at end of period	$ 185	$ 504	$ 185	$ 504