Securities - Amortized Cost and Fair Value of Asset Backed Securities (Detail) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Securities available-for-sale:
Amortized Cost	$ 31,651	$ 27,221
Allowance for Credit Losses	0	0
Unrealized Gains	56	14
Unrealized Losses	(1,677)	(2,298)
Fair Value	30,030	24,937
Securities held-to-maturity:
Amortized Cost	18,293	17,798
Allowance for Credit Losses	0	0
Unrealized Gains	140	8
Unrealized Losses	(296)	(777)
Fair Value	18,137	17,029
U.S. Treasury
Securities available-for-sale:
Amortized Cost	13,895	10,250
Allowance for Credit Losses	0	0
Unrealized Gains	32	7
Unrealized Losses	(107)	(205)
Fair Value	13,820	10,052
Securities held-to-maturity:
Amortized Cost	2,846	2,807
Allowance for Credit Losses	0	0
Unrealized Gains	7	0
Unrealized Losses	(4)	(86)
Fair Value	2,849	2,721
U.S. Government sponsored enterprises
Securities available-for-sale:
Amortized Cost	4,603	5,296
Allowance for Credit Losses	0	0
Unrealized Gains	2	1
Unrealized Losses	(808)	(1,008)
Fair Value	3,797	4,289
Securities held-to-maturity:
Amortized Cost	1,062	1,165
Allowance for Credit Losses	0	0
Unrealized Gains	3	2
Unrealized Losses	(47)	(90)
Fair Value	1,018	1,077
U.S. Government agency issued or guaranteed
Securities available-for-sale:
Amortized Cost	8,750	8,044
Allowance for Credit Losses	0	0
Unrealized Gains	11	5
Unrealized Losses	(752)	(1,071)
Fair Value	8,009	6,978
Securities held-to-maturity:
Amortized Cost	14,383	13,824
Allowance for Credit Losses	0	0
Unrealized Gains	130	6
Unrealized Losses	(245)	(601)
Fair Value	14,268	13,229
Home equity mortgages
Securities available-for-sale:
Amortized Cost	8	11
Allowance for Credit Losses	0	0
Unrealized Gains	0	0
Unrealized Losses	0	(1)
Fair Value	8	10
Corporate loans
Securities available-for-sale:
Amortized Cost	179
Allowance for Credit Losses	0
Unrealized Gains	0
Unrealized Losses	0
Fair Value	179
Other
Securities available-for-sale:
Amortized Cost	85	98
Allowance for Credit Losses	0	0
Unrealized Gains	0	0
Unrealized Losses	(9)	(11)
Fair Value	76	87
Foreign debt securities
Securities available-for-sale:
Amortized Cost	4,131	3,522
Allowance for Credit Losses	0	0
Unrealized Gains	11	1
Unrealized Losses	(1)	(2)
Fair Value	4,141	3,521
Obligations of U.S. states and political subdivisions
Securities held-to-maturity:
Amortized Cost	2	2
Allowance for Credit Losses	0	0
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	$ 2	$ 2

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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