Fair Value - Schedule of Financial Assets and Liabilities Carried at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	$ 743	$ 768
Available-for-sale investment securities:	67,444	58,895
Bank-owned life insurance	7,260	11,183
Derivative asset, collateral, cash offset	1,683	1,860
Derivative liability, collateral, cash offset	1,919	6,103
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	743	768
Available-for-sale investment securities:	67,444	58,895
Derivative asset, Impact of Netting	(11,185)	(18,285)
Bank-owned life insurance	7,260	11,183
Other	804	767
Other, Impact of Netting	0	0
Total	76,251	71,613
Derivative liability, Impact of Netting	(11,421)	(22,528)
Derivative liabilities	7,303	6,596
Total liabilities carried at fair value	7,303	6,596
Recurring | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, Impact of Netting	(11,153)	(18,262)
Bank-owned life insurance	7,260	11,177
Derivative liability, Impact of Netting	(11,421)	(22,527)
Derivative liabilities	7,077	6,377
Recurring | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, Impact of Netting	(32)	(23)
Bank-owned life insurance	0	5
Derivative liability, Impact of Netting	0	(1)
Derivative liabilities	21	0
Recurring | Other derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, Impact of Netting		0
Bank-owned life insurance		1
Recurring | Other derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, Impact of Netting	0	0
Derivative liabilities	205	219
Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	34	34
Recurring | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	122	121
Recurring | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	587	613
Available-for-sale investment securities:	29	52
Recurring | Direct obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	27,380	23,525
Recurring | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	12,749	10,566
Recurring | Total U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	40,129	34,091
Recurring | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	2,471	2,430
Recurring | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	1,996	1,868
Recurring | Non-U.S. sovereign, supranational and non-U.S. agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	16,059	13,939
Recurring | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	3,129	2,821
Recurring | Total non-U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	23,655	21,058
Recurring | Student loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	87	90
Recurring | Collateralized loan obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	3,393	3,453
Recurring | Non-agency CMBS and RMBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	4	4
Recurring | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	91	91
Recurring | Total asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	3,575	3,638
Recurring | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	56	56
Recurring | Quoted Market Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	34	34
Available-for-sale investment securities:	27,380	23,525
Derivative asset	0	22
Other	19	20
Total	27,433	23,601
Derivative liability	29	0
Total liabilities carried at fair value	29	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	16
Derivative liability	8	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	5
Derivative liability	21	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Other derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset		1
Recurring | Quoted Market Prices in Active Markets (Level 1) | Other derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	34	34
Recurring | Quoted Market Prices in Active Markets (Level 1) | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	0	0
Available-for-sale investment securities:	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Direct obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	27,380	23,525
Recurring | Quoted Market Prices in Active Markets (Level 1) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Total U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	27,380	23,525
Recurring | Quoted Market Prices in Active Markets (Level 1) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Non-U.S. sovereign, supranational and non-U.S. agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Total non-U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Student loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Collateralized loan obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Non-agency CMBS and RMBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | Total asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Quoted Market Prices in Active Markets (Level 1) | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	709	734
Available-for-sale investment securities:	40,064	35,370
Derivative asset	18,443	29,445
Other	785	747
Total	60,001	66,296
Derivative liability	18,695	29,124
Total liabilities carried at fair value	18,695	29,124
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	18,411	29,422
Derivative liability	18,490	28,904
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	32	23
Derivative liability	0	1
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Other derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset		0
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Other derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	205	219
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	0	0
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	122	121
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	587	613
Available-for-sale investment securities:	29	52
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Direct obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	12,749	10,566
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Total U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	12,749	10,566
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	2,471	2,430
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	1,996	1,868
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Non-U.S. sovereign, supranational and non-U.S. agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	16,059	13,939
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	3,129	2,821
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Total non-U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	23,655	21,058
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Student loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	87	90
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Collateralized loan obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	3,393	3,453
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Non-agency CMBS and RMBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	4	4
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	91	91
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | Total asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	3,575	3,638
Recurring | Pricing Methods with Significant Observable Market Inputs (Level 2) | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	56	56
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	0	0
Available-for-sale investment securities:	0	0
Derivative asset	2	1
Other	0	0
Total	2	1
Derivative liability	0	0
Total liabilities carried at fair value	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	2	1
Derivative liability	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liability	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Other derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset		0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Other derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets	0	0
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Direct obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Total U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Non-U.S. sovereign, supranational and non-U.S. agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Total non-U.S. debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Student loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Collateralized loan obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Non-agency CMBS and RMBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Total asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	0	0
Recurring | Pricing Methods with Significant Unobservable Market Inputs (Level 3) | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities:	$ 0	$ 0