Accumulated Other Comprehensive Income (Loss) - Impact to Net Income for Items Reclassified out of Accumulated Other Comprehensive Income and into Earnings (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains (losses) on sale of securities	$ 5	$ 12
Amortization of unrealized gains on securities transferred from available-for-sale to held-to-maturity, Interest income	3,022	3,111
Gains (Losses) on derivative hedges	2,650	2,653
Actuarial gains (losses), prior service cost (credit) and transition obligation (asset) amortization	(289)	(310)
Total securities gains (losses), net	5	5
Applicable income taxes	(496)	(558)
Net income	1,412	1,387
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	(45)	(55)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Securities Available-For-Sale [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains (losses) on sale of securities	5	12
Other-than-temporary impairment recognized in earnings		(7)
Total securities gains (losses), net	5	5
Applicable income taxes	(2)	(2)
Net income	3	3
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Securities Transferred From Available For Sale to Held To Maturity [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of unrealized gains on securities transferred from available-for-sale to held-to-maturity, Interest income	7	20
Applicable income taxes	(3)	(7)
Net income	4	13
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Derivative Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains (Losses) on derivative hedges	(49)	(54)
Applicable income taxes	19	21
Net income	(30)	(33)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Retirement Plans [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Actuarial gains (losses), prior service cost (credit) and transition obligation (asset) amortization	(36)	(62)
Applicable income taxes	14	24
Net income	$ (22)	$ (38)