Accumulated Other Comprehensive Income (Loss) - Reconciliation of Transactions Affecting Accumulated Other Comprehensive Income (Loss) Included in Shareholders' Equity (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
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (850)	$ (941)	$ (1,071)	$ (923)
Changes in unrealized gains and losses	206	(675)	507	(795)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Derivative Hedges	(24)	53	(35)	50
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Retirement Plans				(1)
Changes in unrealized gains and losses	182	(622)	472	(746)
Other-than-temporary impairment not recognized in earnings on securities available-for-sale	1	1	1	7
Foreign currency translation adjustment	18	(23)	14	(33)
Reclassification to earnings of realized gains and losses	72	80	145	171
Applicable income taxes	(105)	217	(243)	236
Balance at end of period	(682)	(1,288)	(682)	(1,288)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(63)	(46)	(60)	(40)
Changes in unrealized gains and losses
Other-than-temporary impairment not recognized in earnings on securities available-for-sale
Foreign currency translation adjustment	18	(23)	14	(33)
Reclassification to earnings of realized gains and losses
Applicable income taxes	(6)	9	(5)	13
Balance at end of period	(51)	(60)	(51)	(60)
Unrealized Gains (Losses) on Retirement Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(721)	(1,221)	(743)	(1,265)
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
Foreign currency translation adjustment
Reclassification to earnings of realized gains and losses	36	62	72	124
Applicable income taxes	(14)	(25)	(28)	(42)
Balance at end of period	(699)	(1,184)	(699)	(1,184)
Unrealized Gains (Losses) on Derivative Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(238)	(371)	(261)	(404)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Derivative Hedges	(24)	53	(35)	50
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	45	41	94	95
Applicable income taxes	(8)	(36)	(23)	(54)
Balance at end of period	(225)	(313)	(225)	(313)
Unrealized Gains (Losses) on Securities Transferred From Available For Sale to Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	66	94	70	107
Changes in unrealized gains and losses
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	(9)	(17)	(16)	(37)
Applicable income taxes	3	7	6	14
Balance at end of period	60	84	60	84
Unrealized Gains (Losses) on Securities Available-For-Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	106	603	(77)	679
Changes in unrealized gains and losses	206	(675)	507	(795)
Other-than-temporary impairment not recognized in earnings on securities available-for-sale	1	1	1	7
Foreign currency translation adjustment
Reclassification to earnings of realized gains and losses		(6)	(5)	(11)
Applicable income taxes	(80)	262	(193)	305
Balance at end of period	$ 233	$ 185	$ 233	$ 185