Fair Value - Schedule of Carrying Values and Estimated Fair Values for Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Financial Assets
Investment in marketable equity securities	$ 75	$ 95
Investment securities available for sale	16,661	8,995
Investment securities held to maturity	10,082	10,279
Interest rate & other derivative — non-qualifying hedges	904	159
Financial Liabilities
Fair value of derivative financial instruments	912	486
Carrying Value
Financial Assets
Cash and due from banks	791	518
Interest earning deposits at banks	36,704	5,025
Securities purchased under agreements to resell	549
Investment in marketable equity securities	75	95
Investment securities available for sale	16,661	8,995
Investment securities held to maturity	10,082	10,279
Loans held for sale	54	52
Net loans	129,466	67,720
Accrued interest receivable	833	329
Federal Home Loan Bank stock	19	197
Mortgage servicing rights	25	25
Interest rate & other derivative — non-qualifying hedges	904	159
Financial Liabilities
Deposits with no stated maturity	129,197	78,798
Time deposits	17,036	10,610
Credit balances of factoring clients	1,282	995
Securities sold under customer repurchase agreements	453	436
Other short-term debt		1,750
Long-term borrowings	37,250	4,452
Accrued interest payable	146	57
Fair value of derivative financial instruments	912	486
Estimated Fair Value
Financial Assets
Cash and due from banks	791	518
Interest earning deposits at banks	36,704	5,025
Securities purchased under agreements to resell	549
Investment in marketable equity securities	75	95
Investment securities available for sale	16,661	8,995
Investment securities held to maturity	8,152	8,795
Loans held for sale	54	49
Net loans	125,873	64,312
Accrued interest receivable	833	329
Federal Home Loan Bank stock	19	197
Mortgage servicing rights	47	47
Interest rate & other derivative — non-qualifying hedges	904	159
Financial Liabilities
Deposits with no stated maturity	129,197	78,798
Time deposits	16,990	10,504
Credit balances of factoring clients	1,282	995
Securities sold under customer repurchase agreements	453	436
Other short-term debt		1,750
Long-term borrowings	36,296	4,330
Accrued interest payable	146	57
Fair value of derivative financial instruments	912	486
Estimated Fair Value | Level 1
Financial Assets
Cash and due from banks	791	518
Interest earning deposits at banks	36,704	5,025
Securities purchased under agreements to resell	0
Investment in marketable equity securities	31	32
Investment securities available for sale	0	0
Investment securities held to maturity	0	0
Loans held for sale	0	0
Net loans	0	0
Accrued interest receivable	0	0
Federal Home Loan Bank stock	0	0
Mortgage servicing rights	0	0
Interest rate & other derivative — non-qualifying hedges	0	0
Financial Liabilities
Deposits with no stated maturity	0	0
Time deposits	0	0
Credit balances of factoring clients	0	0
Securities sold under customer repurchase agreements	0	0
Other short-term debt		0
Long-term borrowings	0	0
Accrued interest payable	0	0
Fair value of derivative financial instruments	0	0
Estimated Fair Value | Level 2
Financial Assets
Cash and due from banks	0	0
Interest earning deposits at banks	0	0
Securities purchased under agreements to resell	549
Investment in marketable equity securities	44	63
Investment securities available for sale	16,509	8,821
Investment securities held to maturity	8,152	8,795
Loans held for sale	22	4
Net loans	1,506	1,679
Accrued interest receivable	833	329
Federal Home Loan Bank stock	19	197
Mortgage servicing rights	0	0
Interest rate & other derivative — non-qualifying hedges	898	159
Financial Liabilities
Deposits with no stated maturity	129,197	78,798
Time deposits	16,990	10,504
Credit balances of factoring clients	0	0
Securities sold under customer repurchase agreements	453	436
Other short-term debt		1,750
Long-term borrowings	36,296	4,312
Accrued interest payable	146	57
Fair value of derivative financial instruments	911	486
Estimated Fair Value | Level 3
Financial Assets
Cash and due from banks	0	0
Interest earning deposits at banks	0	0
Securities purchased under agreements to resell	0
Investment in marketable equity securities	0	0
Investment securities available for sale	152	174
Investment securities held to maturity	0	0
Loans held for sale	32	45
Net loans	124,367	62,633
Accrued interest receivable	0	0
Federal Home Loan Bank stock	0	0
Mortgage servicing rights	47	47
Interest rate & other derivative — non-qualifying hedges	6	0
Financial Liabilities
Deposits with no stated maturity	0	0
Time deposits	0	0
Credit balances of factoring clients	1,282	995
Securities sold under customer repurchase agreements	0	0
Other short-term debt		0
Long-term borrowings	0	18
Accrued interest payable	0	0
Fair value of derivative financial instruments	$ 1	$ 0