Fair Value - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	$ 11,894	$ 8,995
Marketable equity securities	76	95
Interest rate & other derivative — non-qualifying hedges	758	159
Fair value of derivative financial instruments	825	486
U.S. Treasury
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	4,634	1,898
Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	4,810	4,795
Commercial mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	1,577	1,604
Municipal bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	257
Fair Value, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	11,894	8,995
Marketable equity securities	76	95
Loans held for sale	42	4
Interest rate & other derivative — non-qualifying hedges	758	159
Fair value of derivative financial instruments	825	486
Fair Value, Recurring | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate & other derivative — non-qualifying hedges	553	158
Fair value of derivative financial instruments	624	482
Fair Value, Recurring | Foreign exchange contract
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate & other derivative — non-qualifying hedges	203	1
Fair value of derivative financial instruments	200	4
Fair Value, Recurring | Other derivative
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate & other derivative — non-qualifying hedges	2	0
Fair value of derivative financial instruments	1	0
Fair Value, Recurring | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Marketable equity securities	24	32
Loans held for sale	0	0
Interest rate & other derivative — non-qualifying hedges	0	0
Fair value of derivative financial instruments	0	0
Fair Value, Recurring | Level 1 | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate & other derivative — non-qualifying hedges	0	0
Fair value of derivative financial instruments	0	0
Fair Value, Recurring | Level 1 | Foreign exchange contract
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate & other derivative — non-qualifying hedges	0	0
Fair value of derivative financial instruments	0	0
Fair Value, Recurring | Level 1 | Other derivative
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate & other derivative — non-qualifying hedges	0	0
Fair value of derivative financial instruments	0	0
Fair Value, Recurring | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	11,743	8,821
Marketable equity securities	52	63
Loans held for sale	42	4
Interest rate & other derivative — non-qualifying hedges	755	159
Fair value of derivative financial instruments	824	486
Fair Value, Recurring | Level 2 | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate & other derivative — non-qualifying hedges	552	158
Fair value of derivative financial instruments	624	482
Fair Value, Recurring | Level 2 | Foreign exchange contract
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate & other derivative — non-qualifying hedges	203	1
Fair value of derivative financial instruments	200	4
Fair Value, Recurring | Level 2 | Other derivative
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate & other derivative — non-qualifying hedges	0	0
Fair value of derivative financial instruments	0	0
Fair Value, Recurring | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	151	174
Marketable equity securities	0	0
Loans held for sale	0	0
Interest rate & other derivative — non-qualifying hedges	3	0
Fair value of derivative financial instruments	1	0
Fair Value, Recurring | Level 3 | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate & other derivative — non-qualifying hedges	1	0
Fair value of derivative financial instruments	0	0
Fair Value, Recurring | Level 3 | Foreign exchange contract
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate & other derivative — non-qualifying hedges	0	0
Fair value of derivative financial instruments	0	0
Fair Value, Recurring | Level 3 | Other derivative
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate & other derivative — non-qualifying hedges	2	0
Fair value of derivative financial instruments	1	0
Fair Value, Recurring | U.S. Treasury
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	4,634	1,898
Fair Value, Recurring | U.S. Treasury | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | U.S. Treasury | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	4,634	1,898
Fair Value, Recurring | U.S. Treasury | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Government agency
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	140	162
Fair Value, Recurring | Government agency | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Government agency | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	140	162
Fair Value, Recurring | Government agency | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	4,810	4,795
Fair Value, Recurring | Residential mortgage-backed securities | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Residential mortgage-backed securities | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	4,810	4,795
Fair Value, Recurring | Residential mortgage-backed securities | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Commercial mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	1,577	1,604
Fair Value, Recurring | Commercial mortgage-backed securities | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Commercial mortgage-backed securities | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	1,577	1,604
Fair Value, Recurring | Commercial mortgage-backed securities | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Corporate bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	476	536
Fair Value, Recurring | Corporate bonds | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Corporate bonds | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	325	362
Fair Value, Recurring | Corporate bonds | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	151	174
Fair Value, Recurring | Municipal bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	257	0
Fair Value, Recurring | Municipal bonds | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Fair Value, Recurring | Municipal bonds | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	257	0
Fair Value, Recurring | Municipal bonds | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	$ 0	$ 0