Fair Value - Carrying Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Financial Assets:
Cash and due from banks	$ 2,976	$ 3,631
Interest-bearing deposits with banks	104,010	106,358
Securities purchased under resale agreements	803	3,012
Investment securities held-to-maturity	42,834	42,271
Financial Liabilities:
Non-interest-bearing	61,797	56,461
Interest-bearing - U.S.	104,962	102,985
Interest-bearing - non-U.S.	84,284	95,589
Securities sold under repurchase agreements	4,277	1,575
Other short-term borrowings	18	128
Pricing Methods with Significant Observable Market Inputs (Level 2)
Financial Assets:
Net loans (excluding leases)	57	8
Reported Amount
Financial Assets:
Cash and due from banks	2,976	3,631
Interest-bearing deposits with banks	104,010	106,358
Securities purchased under resale agreements	803	3,012
Investment securities held-to-maturity	45,203	42,430
Net loans (excluding leases)	35,055	32,445
Other	1	1
Financial Liabilities:
Non-interest-bearing	61,797	56,461
Interest-bearing - U.S.	104,962	102,985
Interest-bearing - non-U.S.	84,284	95,589
Securities sold under repurchase agreements	4,277	1,575
Other short-term borrowings	18	128
Long-term debt	13,922	13,475
Other	1	1
Estimated Fair Value
Financial Assets:
Cash and due from banks	2,976	3,631
Interest-bearing deposits with banks	104,010	106,358
Securities purchased under resale agreements	803	3,012
Investment securities held-to-maturity	42,834	42,271
Net loans (excluding leases)	35,069	32,528
Other	1	1
Financial Liabilities:
Non-interest-bearing	61,797	56,461
Interest-bearing - U.S.	104,962	102,985
Interest-bearing - non-U.S.	84,284	95,589
Securities sold under repurchase agreements	4,277	1,575
Other short-term borrowings	18	128
Long-term debt	13,555	13,552
Other	1	1
Estimated Fair Value | Quoted Market Prices in Active Markets (Level 1)
Financial Assets:
Cash and due from banks	2,976	3,631
Interest-bearing deposits with banks	0	0
Securities purchased under resale agreements	0	0
Investment securities held-to-maturity	702	2,160
Net loans (excluding leases)	0	0
Other	0	0
Financial Liabilities:
Non-interest-bearing	0	0
Interest-bearing - U.S.	0	0
Interest-bearing - non-U.S.	0	0
Securities sold under repurchase agreements	0	0
Other short-term borrowings	0	0
Long-term debt	0	0
Other	0	0
Estimated Fair Value | Pricing Methods with Significant Observable Market Inputs (Level 2)
Financial Assets:
Cash and due from banks	0	0
Interest-bearing deposits with banks	104,010	106,358
Securities purchased under resale agreements	803	3,012
Investment securities held-to-maturity	42,132	40,111
Net loans (excluding leases)	32,802	29,862
Other	1	1
Financial Liabilities:
Non-interest-bearing	61,797	56,461
Interest-bearing - U.S.	104,962	102,985
Interest-bearing - non-U.S.	84,284	95,589
Securities sold under repurchase agreements	4,277	1,575
Other short-term borrowings	18	128
Long-term debt	13,408	13,385
Other	1	1
Estimated Fair Value | Pricing Methods with Significant Unobservable Market Inputs (Level 3)
Financial Assets:
Cash and due from banks	0	0
Interest-bearing deposits with banks	0	0
Securities purchased under resale agreements	0	0
Investment securities held-to-maturity	0	0
Net loans (excluding leases)	2,267	2,666
Other	0	0
Financial Liabilities:
Non-interest-bearing	0	0
Interest-bearing - U.S.	0	0
Interest-bearing - non-U.S.	0	0
Securities sold under repurchase agreements	0	0
Other short-term borrowings	0	0
Long-term debt	147	167
Other	$ 0	$ 0