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, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains (losses) on sale of investment securities	$ 1	$ 20	$ 38	$ 88
Amortization of unrealized gains on securities transferred from available-for-sale to held-to-maturity, Interest income	4,728	3,409	11,971	10,132
Realized gains (losses) on derivative hedges	(901)	(238)	(1,536)	(761)
Actuarial gains (losses) and prior service cost (credit) amortization	(336)	(291)	(998)	(937)
Applicable income taxes	(481)	(564)	(1,292)	(1,722)
Net income	1,816	2,034	4,908	6,307
Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	(139)	(20)	(252)	(25)
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Investment Securities Available-For-Sale [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains (losses) on sale of investment securities	1	20	38	88
Applicable income taxes		(5)	(9)	(22)
Net income	1	15	29	66
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Investment 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	(147)		(250)
Applicable income taxes	37		63
Net income	(110)		(187)
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	(8)	(8)	(29)	(4)
Applicable income taxes	2	2	7	1
Net income	(6)	(6)	(22)	(3)
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	(32)	(39)	(96)	(118)
Applicable income taxes	8	10	24	30
Net income	$ (24)	$ (29)	$ (72)	$ (88)