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
	Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (1,071)	$ (923)
Changes in unrealized gains and losses	301	(120)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Derivative Hedges	(11)	(3)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Retirement Plans		(1)
Changes in unrealized gains and losses	290	(124)
Other-than-temporary impairment not recognized in earnings on securities available-for-sale		6
Foreign currency translation adjustment	(4)	(10)
Reclassification to earnings of realized gains and losses	73	91
Applicable income taxes	(138)	19
Balance at end of period	(850)	(941)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(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	(4)	(10)
Reclassification to earnings of realized gains and losses
Applicable income taxes	1	4
Balance at end of period	(63)	(46)
Unrealized Gains (Losses) on Retirement Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(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
Applicable income taxes	(14)	(17)
Balance at end of period	(721)	(1,221)
Unrealized Gains (Losses) on Derivative Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(261)	(404)
Changes in unrealized gains and losses, Unrealized Gains (Losses) on Derivative Hedges	(11)	(3)
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	49	54
Applicable income taxes	(15)	(18)
Balance at end of period	(238)	(371)
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	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	(7)	(20)
Applicable income taxes	3	7
Balance at end of period	66	94
Unrealized Gains (Losses) on Securities Available-For-Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(77)	679
Changes in unrealized gains and losses	301	(120)
Other-than-temporary impairment not recognized in earnings on securities available-for-sale		6
Foreign currency translation adjustment
Reclassification to earnings of realized gains and losses	(5)	(5)
Applicable income taxes	(113)	43
Balance at end of period	$ 106	$ 603