Accumulated Other Comprehensive Income (Loss) - Reconciliation of Transactions Affecting Accumulated Other Comprehensive Income (Loss) Included in Shareholders' Equity (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		$ (11,407)	$ (1,943)
Changes in unrealized gains (losses)		1,305	(6,754)
Changes in unrealized gains (losses)		204
Changes in unrealized gains (losses)		1
Changes in unrealized gains (losses)		1,510	(6,754)
Foreign currency translation adjustment	[1]	(1)
Reclassification to earnings of realized (gains) losses		158	67
Applicable income taxes		(413)	1,692
Balance at end of period		(10,153)	(6,938)
Unrealized Gains (Losses) on Investment Securities Available-For-Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(6,378)	540
Changes in unrealized gains (losses)		1,305	(6,754)
Reclassification to earnings of realized (gains) losses		32	(18)
Applicable income taxes		(328)	1,714
Balance at end of period		(5,369)	(4,518)
Unrealized Gains (Losses) on Investment Securities Transferred From Available For Sale to Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(3,933)	(935)
Reclassification to earnings of realized (gains) losses		121	42
Applicable income taxes		(31)	(11)
Balance at end of period		(3,843)	(904)
Unrealized Gains (Losses) on Derivative Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(114)	(85)
Changes in unrealized gains (losses)		204
Reclassification to earnings of realized (gains) losses		7	11
Applicable income taxes		(54)	(3)
Balance at end of period		43	(77)
Unrealized Gains (Losses) on Retirement Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(939)	(1,426)
Changes in unrealized gains (losses)		1
Reclassification to earnings of realized (gains) losses		(2)	32
Applicable income taxes			(8)
Balance at end of period		(940)	(1,402)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(43)	(37)
Foreign currency translation adjustment	[1]	(1)
Balance at end of period		$ (44)	$ (37)

[1] Represents the impact of changes in foreign currency exchange rates on the Company’s investment in foreign operations and related hedges.