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	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains (losses) on sale of securities	$ 12		$ 19
Amortization of unrealized gains on securities transferred from available-for-sale to held-to-maturity, Interest income	3,320	$ 3,117	9,793	$ 9,246
Realized gains (losses) on derivative hedges	2,893	2,768	8,573	8,182
Actuarial gains (losses) and prior service cost (credit) amortization	(280)	(285)	(858)	(895)
Total securities gains (losses), net	10	(1)	16	(1)
Applicable income taxes	(566)	(534)	(1,612)	(1,541)
Net income	1,516	1,503	4,453	4,444
Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	(32)	(60)	(120)	(181)
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	12		19
Other-than-temporary impairment recognized in earnings	(2)	(1)	(3)	(1)
Total securities gains (losses), net	10	(1)	16	(1)
Applicable income taxes	(4)		(6)
Net income	6	(1)	10	(1)
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	5	6	14	20
Applicable income taxes	(1)	(2)	(5)	(7)
Net income	4	4	9	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]
Realized gains (losses) on derivative hedges	(28)	(48)	(104)	(147)
Applicable income taxes	11	19	40	57
Net income	(17)	(29)	(64)	(90)
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) and prior service cost (credit) amortization	(41)	(55)	(122)	(167)
Applicable income taxes	16	21	47	64
Net income	$ (25)	$ (34)	$ (75)	$ (103)

This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The amount of other than temporary impairment losses on investments in debt and equity securities categorized as Available-for-sale which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

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