Derivative Instruments and Hedging Activities - Fair Values of Derivative Contracts (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivative Assets
Total gross derivatives	$ 367,699	$ 418,179
Amounts offset against counterparty netting	(280,069)	(323,543)
Amounts offset against cash collateral netting	(46,780)	(56,786)
Total in Trading assets	40,850	37,850
Amounts not offset against financial instruments collateral	(14,142)	(13,319)
Amounts not offset against other cash collateral	(413)	(391)
Net amounts	26,295	24,140
Net amounts for which master netting or collateral agreements are not in place or may not be legally enforceable	5,039	3,743
Derivative Liabilities
Total gross derivatives	364,317	420,416
Amounts offset against counterparty netting	(280,069)	(323,543)
Amounts offset against cash collateral netting	(44,462)	(51,935)
Total in Trading liabilities	39,786	44,938
Amounts not offset against financial instruments collateral	(8,931)	(12,118)
Amounts not offset against other cash collateral	(30)	(65)
Net amounts	30,825	32,755
Net amounts for which master netting or collateral agreements are not in place or may not be legally enforceable	7,637	6,746
Bilateral OTC
Derivative Assets
Total gross derivatives	312,989	365,896
Amounts offset against counterparty netting	(230,463)	(276,682)
Amounts offset against cash collateral netting	(45,005)	(54,921)
Total in Trading assets	37,521	34,293
Amounts not offset against financial instruments collateral	(14,142)	(13,319)
Amounts not offset against other cash collateral	(413)	(391)
Net amounts	22,966	20,583
Derivative Liabilities
Total gross derivatives	307,382	367,348
Amounts offset against counterparty netting	(230,463)	(276,682)
Amounts offset against cash collateral netting	(43,611)	(51,112)
Total in Trading liabilities	33,308	39,554
Amounts not offset against financial instruments collateral	(6,818)	(10,598)
Amounts not offset against other cash collateral	(25)	(62)
Net amounts	26,465	28,894
Cleared OTC
Derivative Assets
Total gross derivatives	14,990	14,184
Amounts offset against counterparty netting	(13,140)	(11,601)
Amounts offset against cash collateral netting	(1,774)	(1,865)
Total in Trading assets	76	718
Amounts not offset against financial instruments collateral	0	0
Amounts not offset against other cash collateral	0	0
Net amounts	76	718
Derivative Liabilities
Total gross derivatives	15,015	12,442
Amounts offset against counterparty netting	(13,140)	(11,601)
Amounts offset against cash collateral netting	(851)	(823)
Total in Trading liabilities	1,024	18
Amounts not offset against financial instruments collateral	0	0
Amounts not offset against other cash collateral	(5)	(3)
Net amounts	1,019	15
Exchange- Traded
Derivative Assets
Total gross derivatives	39,720	38,099
Amounts offset against counterparty netting	(36,466)	(35,260)
Amounts offset against cash collateral netting	(1)	0
Total in Trading assets	3,253	2,839
Amounts not offset against financial instruments collateral	0	0
Amounts not offset against other cash collateral	0	0
Net amounts	3,253	2,839
Derivative Liabilities
Total gross derivatives	41,920	40,626
Amounts offset against counterparty netting	(36,466)	(35,260)
Amounts offset against cash collateral netting	0	0
Total in Trading liabilities	5,454	5,366
Amounts not offset against financial instruments collateral	(2,113)	(1,520)
Amounts not offset against other cash collateral	0	0
Net amounts	3,341	3,846
Designated as accounting hedges
Derivative Assets
Total gross derivatives	797	955
Derivative Liabilities
Total gross derivatives	49	409
Designated as accounting hedges | Bilateral OTC
Derivative Assets
Total gross derivatives	763	951
Derivative Liabilities
Total gross derivatives	3	291
Designated as accounting hedges | Cleared OTC
Derivative Assets
Total gross derivatives	34	4
Derivative Liabilities
Total gross derivatives	46	118
Designated as accounting hedges | Exchange- Traded
Derivative Assets
Total gross derivatives	0	0
Derivative Liabilities
Total gross derivatives	0	0
Designated as accounting hedges | Interest rate
Derivative Assets
Total gross derivatives	473	948
Derivative Liabilities
Total gross derivatives	6	19
Designated as accounting hedges | Interest rate | Bilateral OTC
Derivative Assets
Total gross derivatives	449	946
Derivative Liabilities
Total gross derivatives	0	0
Designated as accounting hedges | Interest rate | Cleared OTC
Derivative Assets
Total gross derivatives	24	2
Derivative Liabilities
Total gross derivatives	6	19
Designated as accounting hedges | Interest rate | Exchange- Traded
Derivative Assets
Total gross derivatives	0	0
Derivative Liabilities
Total gross derivatives	0	0
Designated as accounting hedges | Foreign exchange
Derivative Assets
Total gross derivatives	324	7
Derivative Liabilities
Total gross derivatives	43	390
Designated as accounting hedges | Foreign exchange | Bilateral OTC
Derivative Assets
Total gross derivatives	314	5
Derivative Liabilities
Total gross derivatives	3	291
Designated as accounting hedges | Foreign exchange | Cleared OTC
Derivative Assets
Total gross derivatives	10	2
Derivative Liabilities
Total gross derivatives	40	99
Designated as accounting hedges | Foreign exchange | Exchange- Traded
Derivative Assets
Total gross derivatives	0	0
Derivative Liabilities
Total gross derivatives	0	0
Not designated as accounting hedges
Derivative Assets
Total gross derivatives	366,902	417,224
Derivative Liabilities
Total gross derivatives	364,268	420,007
Not designated as accounting hedges | Bilateral OTC
Derivative Assets
Total gross derivatives	312,226	364,945
Derivative Liabilities
Total gross derivatives	307,379	367,057
Not designated as accounting hedges | Cleared OTC
Derivative Assets
Total gross derivatives	14,956	14,180
Derivative Liabilities
Total gross derivatives	14,969	12,324
Not designated as accounting hedges | Exchange- Traded
Derivative Assets
Total gross derivatives	39,720	38,099
Derivative Liabilities
Total gross derivatives	41,920	40,626
Economic loan hedges | Credit
Derivative Assets
Total gross derivatives	26	53
Derivative Liabilities
Total gross derivatives	262	195
Economic loan hedges | Credit | Bilateral OTC
Derivative Assets
Total gross derivatives	1	2
Derivative Liabilities
Total gross derivatives	20	18
Economic loan hedges | Credit | Cleared OTC
Derivative Assets
Total gross derivatives	25	51
Derivative Liabilities
Total gross derivatives	242	177
Economic loan hedges | Credit | Exchange- Traded
Derivative Assets
Total gross derivatives	0	0
Derivative Liabilities
Total gross derivatives	0	0
Other derivatives | Interest rate
Derivative Assets
Total gross derivatives	190,234	232,538
Derivative Liabilities
Total gross derivatives	176,223	218,619
Other derivatives | Interest rate | Bilateral OTC
Derivative Assets
Total gross derivatives	180,315	221,895
Derivative Liabilities
Total gross derivatives	166,601	210,015
Other derivatives | Interest rate | Cleared OTC
Derivative Assets
Total gross derivatives	9,460	10,343
Derivative Liabilities
Total gross derivatives	8,935	7,965
Other derivatives | Interest rate | Exchange- Traded
Derivative Assets
Total gross derivatives	459	300
Derivative Liabilities
Total gross derivatives	687	639
Other derivatives | Credit
Derivative Assets
Total gross derivatives	9,428	7,488
Derivative Liabilities
Total gross derivatives	9,862	7,957
Other derivatives | Credit | Bilateral OTC
Derivative Assets
Total gross derivatives	5,572	5,341
Derivative Liabilities
Total gross derivatives	5,553	5,275
Other derivatives | Credit | Cleared OTC
Derivative Assets
Total gross derivatives	3,856	2,147
Derivative Liabilities
Total gross derivatives	4,309	2,682
Other derivatives | Credit | Exchange- Traded
Derivative Assets
Total gross derivatives	0	0
Derivative Liabilities
Total gross derivatives	0	0
Other derivatives | Foreign exchange
Derivative Assets
Total gross derivatives	82,696	94,052
Derivative Liabilities
Total gross derivatives	79,020	94,518
Other derivatives | Foreign exchange | Bilateral OTC
Derivative Assets
Total gross derivatives	81,019	92,334
Derivative Liabilities
Total gross derivatives	77,495	92,975
Other derivatives | Foreign exchange | Cleared OTC
Derivative Assets
Total gross derivatives	1,615	1,639
Derivative Liabilities
Total gross derivatives	1,483	1,500
Other derivatives | Foreign exchange | Exchange- Traded
Derivative Assets
Total gross derivatives	62	79
Derivative Liabilities
Total gross derivatives	42	43
Other derivatives | Equity
Derivative Assets
Total gross derivatives	67,915	68,444
Derivative Liabilities
Total gross derivatives	84,703	86,528
Other derivatives | Equity | Bilateral OTC
Derivative Assets
Total gross derivatives	32,417	34,278
Derivative Liabilities
Total gross derivatives	47,147	49,943
Other derivatives | Equity | Cleared OTC
Derivative Assets
Total gross derivatives	0	0
Derivative Liabilities
Total gross derivatives	0	0
Other derivatives | Equity | Exchange- Traded
Derivative Assets
Total gross derivatives	35,498	34,166
Derivative Liabilities
Total gross derivatives	37,556	36,585
Other derivatives | Commodity and other
Derivative Assets
Total gross derivatives	16,603	14,649
Derivative Liabilities
Total gross derivatives	14,198	12,190
Other derivatives | Commodity and other | Bilateral OTC
Derivative Assets
Total gross derivatives	12,902	11,095
Derivative Liabilities
Total gross derivatives	10,563	8,831
Other derivatives | Commodity and other | Cleared OTC
Derivative Assets
Total gross derivatives	0	0
Derivative Liabilities
Total gross derivatives	0	0
Other derivatives | Commodity and other | Exchange- Traded
Derivative Assets
Total gross derivatives	3,701	3,554
Derivative Liabilities
Total gross derivatives	$ 3,635	$ 3,359