Accumulated Other Comprehensive Income (Loss) - Impact to Consolidated Statement of Income for Items Reclassified Out of Accumulated Other Comprehensive Income and into Earnings (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
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains (losses) on sale of securities	$ 9	$ 21	$ 21	$ 30
Amortization of unrealized gains on securities transferred from available-for-sale to held-to-maturity, Interest income	3,038	3,228	6,149	6,460
Gains (Losses) on derivative hedges	2,616	2,658	5,269	5,292
Actuarial gains (losses), prior service cost (credit) and transition obligation (asset) amortization	(277)	(229)	(587)	(489)
Total securities gains (losses), net	6	(19)	11	(19)
Applicable income taxes	(529)	(564)	(1,087)	(1,091)
Net income	1,444	1,378	2,831	2,683
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	(49)		(104)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains (losses) on sale of securities	9		21
Other-than-temporary impairment recognized in earnings	(3)		(10)
Total securities gains (losses), net	6		11
Applicable income taxes	(2)		(4)
Net income	4		7
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Gain Loss 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	17		37
Applicable income taxes	(7)		(14)
Net income	10		23
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains (Losses) on derivative hedges	(41)		(95)
Applicable income taxes	16		37
Net income	(25)		(58)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Actuarial gains (losses), prior service cost (credit) and transition obligation (asset) amortization	(62)		(124)
Applicable income taxes	24		48
Net income	$ (38)		$ (76)