Investment Securities - Unrealized Losses and Fair Value of Investment Securities in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	$ 12	$ 34
Less Than Twelve Months, Fair Value	3,210	4,262
More Than Twelve Months, Gross Unrealized Losses	669	695
More Than Twelve Months, Fair Value	3,508	3,637
Total Gross Unrealized Losses	681	729
Total Fair Value	6,718	7,899
Residential MBS issued by GSEs and GNMA
Debt Securities, Available-for-sale [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	3	18
Less Than Twelve Months, Fair Value	1,061	1,793
More Than Twelve Months, Gross Unrealized Losses	352	392
More Than Twelve Months, Fair Value	1,471	1,482
Total Gross Unrealized Losses	355	410
Total Fair Value	2,532	3,275
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	4	3
Less Than Twelve Months, Fair Value	1,948	2,185
More Than Twelve Months, Gross Unrealized Losses	0	0
More Than Twelve Months, Fair Value	0	0
Total Gross Unrealized Losses	4	3
Total Fair Value	1,948	2,185
Private label residential MBS
Debt Securities, Available-for-sale [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	0	0
Less Than Twelve Months, Fair Value	0	0
More Than Twelve Months, Gross Unrealized Losses	175	201
More Than Twelve Months, Fair Value	893	939
Total Gross Unrealized Losses	175	201
Total Fair Value	893	939
Tax-exempt
Debt Securities, Available-for-sale [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	0	1
Less Than Twelve Months, Fair Value	0	32
More Than Twelve Months, Gross Unrealized Losses	113	75
More Than Twelve Months, Fair Value	723	813
Total Gross Unrealized Losses	113	76
Total Fair Value	723	845
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	0	0
Less Than Twelve Months, Fair Value	0	0
More Than Twelve Months, Gross Unrealized Losses	17	21
More Than Twelve Months, Fair Value	339	362
Total Gross Unrealized Losses	17	21
Total Fair Value	339	362
Corporate Bond Securities, With ACL
Debt Securities, Available-for-sale [Line Items]
Total Gross Unrealized Losses	1	1
Total Fair Value	8	8
Commercial MBS issued by GSEs and GNMA
Debt Securities, Available-for-sale [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	1	10
Less Than Twelve Months, Fair Value	170	220
More Than Twelve Months, Gross Unrealized Losses	8	1
More Than Twelve Months, Fair Value	66	16
Total Gross Unrealized Losses	9	11
Total Fair Value	236	236
Other
Debt Securities, Available-for-sale [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	4	2
Less Than Twelve Months, Fair Value	31	32
More Than Twelve Months, Gross Unrealized Losses	4	5
More Than Twelve Months, Fair Value	16	25
Total Gross Unrealized Losses	8	7
Total Fair Value	$ 47	$ 57

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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