Investment Securities - Schedule of Marketable Securities (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	$ 76,117	$ 73,440
Available for sale, gross unrealized gains	74	404
Available for sale, gross unrealized losses	1,843	445
Available-for-sale, fair value	74,348	73,399
Held to maturity, amortized cost	45,203	42,430
Investment securities held-to-maturity	42,834	42,271
Allowance for credit losses on available-for-sale securities	2	2
US Treasury and federal agencies, direct obligations
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	21,687	18,111
Available for sale, gross unrealized gains	14	24
Available for sale, gross unrealized losses	758	196
Available-for-sale, fair value	20,943	17,939
Held to maturity, amortized cost	720	2,170
Held to maturity, gross unrealized gains	2	10
Held to maturity, gross unrealized losses	0	0
Investment securities held-to-maturity	722	2,180
US Treasury and federal agencies, mortgage-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	19,204	18,154
Available for sale, gross unrealized gains	17	148
Available for sale, gross unrealized losses	480	94
Available-for-sale, fair value	18,741	18,208
Held to maturity, amortized cost	35,784	33,481
Held to maturity, gross unrealized gains	18	362
Held to maturity, gross unrealized losses	2,309	578
Investment securities held-to-maturity	33,493	33,265
Total U.S. Treasury and federal agencies
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	40,891	36,265
Available for sale, gross unrealized gains	31	172
Available for sale, gross unrealized losses	1,238	290
Available-for-sale, fair value	39,684	36,147
Held to maturity, amortized cost	36,504	35,651
Held to maturity, gross unrealized gains	20	372
Held to maturity, gross unrealized losses	2,309	578
Investment securities held-to-maturity	34,215	35,445
Non-U.S. debt securities, mortgage-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	2,272	1,986
Available for sale, gross unrealized gains	6	12
Available for sale, gross unrealized losses	10	3
Available-for-sale, fair value	2,268	1,995
Non-U.S. debt securities, asset-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	2,073	2,087
Available for sale, gross unrealized gains	1	2
Available for sale, gross unrealized losses	8	2
Available-for-sale, fair value	2,066	2,087
Non-U.S. sovereign, supranational and non-U.S. agency
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	21,123	23,533
Available for sale, gross unrealized gains	15	114
Available for sale, gross unrealized losses	409	100
Available-for-sale, fair value	20,729	23,547
Held to maturity, amortized cost	3,763	1,564
Held to maturity, gross unrealized gains	0	0
Held to maturity, gross unrealized losses	70	9
Investment securities held-to-maturity	3,693	1,555
Non-U.S. debt securities, other
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	3,494	3,113
Available for sale, gross unrealized gains	5	17
Available for sale, gross unrealized losses	110	32
Available-for-sale, fair value	3,389	3,098
Total non-U.S. debt securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	28,962	30,719
Available for sale, gross unrealized gains	27	145
Available for sale, gross unrealized losses	537	137
Available-for-sale, fair value	28,452	30,727
Held to maturity, amortized cost	3,763	1,564
Held to maturity, gross unrealized gains	0	0
Held to maturity, gross unrealized losses	70	9
Investment securities held-to-maturity	3,693	1,555
Asset-backed securities, student loans
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	186	209
Available for sale, gross unrealized gains	2	2
Available for sale, gross unrealized losses	1	0
Available-for-sale, fair value	187	211
Held to maturity, amortized cost	4,651	4,908
Held to maturity, gross unrealized gains	16	48
Held to maturity, gross unrealized losses	47	14
Investment securities held-to-maturity	4,620	4,942
Asset-backed securities, collateralized loan obligations
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	2,420	2,155
Available for sale, gross unrealized gains	0	2
Available for sale, gross unrealized losses	9	2
Available-for-sale, fair value	2,411	2,155
Non-agency CMBS and RMBS
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	170	52
Available for sale, gross unrealized gains	0	0
Available for sale, gross unrealized losses	2	0
Available-for-sale, fair value	168	52
Held to maturity, amortized cost	285	307
Held to maturity, gross unrealized gains	21	22
Held to maturity, gross unrealized losses	0	0
Investment securities held-to-maturity	306	329
Asset-backed securities, other
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	90	90
Available for sale, gross unrealized gains	0	1
Available for sale, gross unrealized losses	0	0
Available-for-sale, fair value	90	91
Total asset-backed securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	2,866	2,506
Available for sale, gross unrealized gains	2	5
Available for sale, gross unrealized losses	12	2
Available-for-sale, fair value	2,856	2,509
Held to maturity, amortized cost	4,936	5,215
Held to maturity, gross unrealized gains	37	70
Held to maturity, gross unrealized losses	47	14
Investment securities held-to-maturity	4,926	5,271
State and political subdivisions
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	1,197	1,216
Available for sale, gross unrealized gains	12	59
Available for sale, gross unrealized losses	7	3
Available-for-sale, fair value	1,202	1,272
Other U.S. debt securities
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	2,201	2,734
Available for sale, gross unrealized gains	2	23
Available for sale, gross unrealized losses	49	13
Available-for-sale, fair value	2,154	2,744
Including MMLF
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Held to maturity, amortized cost	45,203	42,430
Held to maturity, gross unrealized gains	57	442
Held to maturity, gross unrealized losses	2,426	601
Investment securities held-to-maturity	42,834	42,271
Non-US Collateralized Loan Obligations
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	920	830
Non-U.S. debt securities, corporate bonds
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	$ 1,800	1,530
Federal family education loan program
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Federal government credit support guarantee, percentage minimum	97.00%
US debt securities, corporate bonds
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Available for sale, amortized cost	$ 2,030	2,440
Non-agency CMBS
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Held to maturity, amortized cost	273	292
Non-agency RMBS
Available-For-Sale and Held-To-Maturity-Securities [Line Items]
Held to maturity, amortized cost	$ 12	$ 14