Fair Value - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	$ 16,661	$ 8,995
Marketable equity securities	75	95
Total derivative assets	904	159
Total derivative liabilities	912	486
U.S. Treasury
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	8,647	1,898
Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	5,600	4,795
Commercial mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	1,797	1,604
Municipal bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	10
Fair Value, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	16,661	8,995
Marketable equity securities	75	95
Loans held for sale	22	4
Total derivative assets	904	159
Total derivative liabilities	912	486
Fair Value, Recurring | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total derivative assets	748	158
Total derivative liabilities	781	482
Fair Value, Recurring | Foreign exchange contract
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total derivative assets	151	1
Total derivative liabilities	130	4
Fair Value, Recurring | Other derivative
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total derivative assets	5
Total derivative liabilities	1
Fair Value, Recurring | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0	0
Marketable equity securities	31	32
Loans held for sale	0	0
Total derivative assets	0	0
Total derivative liabilities	0	0
Fair Value, Recurring | Level 1 | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Fair Value, Recurring | Level 1 | Foreign exchange contract
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Fair Value, Recurring | Level 1 | Other derivative
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total derivative assets	0
Total derivative liabilities	0
Fair Value, Recurring | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	16,509	8,821
Marketable equity securities	44	63
Loans held for sale	22	4
Total derivative assets	898	159
Total derivative liabilities	911	486
Fair Value, Recurring | Level 2 | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total derivative assets	747	158
Total derivative liabilities	781	482
Fair Value, Recurring | Level 2 | Foreign exchange contract
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total derivative assets	151	1
Total derivative liabilities	130	4
Fair Value, Recurring | Level 2 | Other derivative
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total derivative assets	0
Total derivative liabilities	0
Fair Value, Recurring | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	152	174
Marketable equity securities	0	0
Loans held for sale	0	0
Total derivative assets	6	0
Total derivative liabilities	1	0
Fair Value, Recurring | Level 3 | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total derivative assets	1	0
Total derivative liabilities	0	0
Fair Value, Recurring | Level 3 | Foreign exchange contract
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Fair Value, Recurring | Level 3 | Other derivative
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total derivative assets	5
Total derivative liabilities	1
Fair Value, Recurring | U.S. Treasury
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	8,647	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	8,647	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	129	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	129	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	5,600	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	5,600	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	1,797	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	1,797	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	478	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	326	362
Fair Value, Recurring | Corporate Bonds | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	152	$ 174
Fair Value, Recurring | Municipal bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	10
Fair Value, Recurring | Municipal bonds | Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0
Fair Value, Recurring | Municipal bonds | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	10
Fair Value, Recurring | Municipal bonds | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	$ 0