Derivative Instruments and Hedging Activities - Fair Values of Derivative Contracts (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivative Assets
Total gross derivatives	$ 356,697	$ 288,585
Amounts offset against counterparty netting	(274,880)	(220,028)
Amounts offset against cash collateral netting	(49,193)	(39,384)
Total in Trading assets	32,624	29,173
Amounts not offset against financial instruments collateral	(14,340)	(12,467)
Amounts not offset against other cash collateral	(35)	(31)
Net amounts	18,249	16,675
Net amounts for which master netting or collateral agreements are not in place or may not be legally enforceable	2,132	2,206
Derivative Liabilities
Total gross derivatives	347,532	275,439
Amounts offset against counterparty netting	(274,880)	(220,028)
Amounts offset against cash collateral netting	(37,250)	(28,153)
Total in Trading liabilities	35,402	27,258
Amounts not offset against financial instruments collateral	(15,849)	(5,475)
Amounts not offset against other cash collateral	(53)	(54)
Net amounts	19,500	21,729
Net amounts for which master netting or collateral agreements are not in place or may not be legally enforceable	3,054	4,773
Bilateral OTC
Derivative Assets
Total gross derivatives	320,683	255,911
Amounts offset against counterparty netting	(242,002)	(190,220)
Amounts offset against cash collateral netting	(47,994)	(38,204)
Total in Trading assets	30,687	27,487
Amounts not offset against financial instruments collateral	(14,340)	(12,467)
Amounts not offset against other cash collateral	(35)	(31)
Net amounts	16,312	14,989
Derivative Liabilities
Total gross derivatives	312,781	243,576
Amounts offset against counterparty netting	(242,002)	(190,220)
Amounts offset against cash collateral netting	(36,520)	(27,860)
Total in Trading liabilities	34,259	25,496
Amounts not offset against financial instruments collateral	(15,526)	(4,709)
Amounts not offset against other cash collateral	(26)	(53)
Net amounts	18,707	20,734
Cleared OTC
Derivative Assets
Total gross derivatives	9,956	6,704
Amounts offset against counterparty netting	(8,580)	(5,260)
Amounts offset against cash collateral netting	(1,199)	(1,180)
Total in Trading assets	177	264
Amounts not offset against financial instruments collateral	0	0
Amounts not offset against other cash collateral	0	0
Net amounts	177	264
Derivative Liabilities
Total gross derivatives	9,524	5,603
Amounts offset against counterparty netting	(8,580)	(5,260)
Amounts offset against cash collateral netting	(730)	(293)
Total in Trading liabilities	214	50
Amounts not offset against financial instruments collateral	0	0
Amounts not offset against other cash collateral	(27)	(1)
Net amounts	187	49
Exchange- Traded
Derivative Assets
Total gross derivatives	26,058	25,970
Amounts offset against counterparty netting	(24,298)	(24,548)
Amounts offset against cash collateral netting	0	0
Total in Trading assets	1,760	1,422
Amounts not offset against financial instruments collateral	0	0
Amounts not offset against other cash collateral	0	0
Net amounts	1,760	1,422
Derivative Liabilities
Total gross derivatives	25,227	26,260
Amounts offset against counterparty netting	(24,298)	(24,548)
Amounts offset against cash collateral netting	0	0
Total in Trading liabilities	929	1,712
Amounts not offset against financial instruments collateral	(323)	(766)
Amounts not offset against other cash collateral	0	0
Net amounts	606	946
Designated as accounting hedges
Derivative Assets
Total gross derivatives	885	548
Derivative Liabilities
Total gross derivatives	46	262
Designated as accounting hedges | Bilateral OTC
Derivative Assets
Total gross derivatives	875	539
Derivative Liabilities
Total gross derivatives	26	238
Designated as accounting hedges | Cleared OTC
Derivative Assets
Total gross derivatives	10	9
Derivative Liabilities
Total gross derivatives	20	24
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	763	513
Derivative Liabilities
Total gross derivatives	1	176
Designated as accounting hedges | Interest rate | Bilateral OTC
Derivative Assets
Total gross derivatives	761	512
Derivative Liabilities
Total gross derivatives	0	176
Designated as accounting hedges | Interest rate | Cleared OTC
Derivative Assets
Total gross derivatives	2	1
Derivative Liabilities
Total gross derivatives	1	0
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	122	35
Derivative Liabilities
Total gross derivatives	45	86
Designated as accounting hedges | Foreign exchange | Bilateral OTC
Derivative Assets
Total gross derivatives	114	27
Derivative Liabilities
Total gross derivatives	26	62
Designated as accounting hedges | Foreign exchange | Cleared OTC
Derivative Assets
Total gross derivatives	8	8
Derivative Liabilities
Total gross derivatives	19	24
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	355,812	288,037
Derivative Liabilities
Total gross derivatives	347,486	275,177
Not designated as accounting hedges | Bilateral OTC
Derivative Assets
Total gross derivatives	319,808	255,372
Derivative Liabilities
Total gross derivatives	312,755	243,338
Not designated as accounting hedges | Cleared OTC
Derivative Assets
Total gross derivatives	9,946	6,695
Derivative Liabilities
Total gross derivatives	9,504	5,579
Not designated as accounting hedges | Exchange- Traded
Derivative Assets
Total gross derivatives	26,058	25,970
Derivative Liabilities
Total gross derivatives	25,227	26,260
Not designated as accounting hedges | Interest rate
Derivative Assets
Total gross derivatives	223,413	158,352
Derivative Liabilities
Total gross derivatives	214,303	145,924
Not designated as accounting hedges | Interest rate | Bilateral OTC
Derivative Assets
Total gross derivatives	216,358	153,768
Derivative Liabilities
Total gross derivatives	208,515	142,592
Not designated as accounting hedges | Interest rate | Cleared OTC
Derivative Assets
Total gross derivatives	6,090	3,887
Derivative Liabilities
Total gross derivatives	4,956	2,669
Not designated as accounting hedges | Interest rate | Exchange- Traded
Derivative Assets
Total gross derivatives	965	697
Derivative Liabilities
Total gross derivatives	832	663
Not designated as accounting hedges | Credit
Derivative Assets
Total gross derivatives	7,719	6,128
Derivative Liabilities
Total gross derivatives	8,105	6,153
Not designated as accounting hedges | Credit | Bilateral OTC
Derivative Assets
Total gross derivatives	4,932	4,630
Derivative Liabilities
Total gross derivatives	4,649	4,545
Not designated as accounting hedges | Credit | Cleared OTC
Derivative Assets
Total gross derivatives	2,787	1,498
Derivative Liabilities
Total gross derivatives	3,456	1,608
Not designated as accounting hedges | Credit | Exchange- Traded
Derivative Assets
Total gross derivatives	0	0
Derivative Liabilities
Total gross derivatives	0	0
Not designated as accounting hedges | Foreign exchange
Derivative Assets
Total gross derivatives	64,510	63,211
Derivative Liabilities
Total gross derivatives	66,239	63,420
Not designated as accounting hedges | Foreign exchange | Bilateral OTC
Derivative Assets
Total gross derivatives	63,326	61,846
Derivative Liabilities
Total gross derivatives	65,081	62,099
Not designated as accounting hedges | Foreign exchange | Cleared OTC
Derivative Assets
Total gross derivatives	1,069	1,310
Derivative Liabilities
Total gross derivatives	1,092	1,302
Not designated as accounting hedges | Foreign exchange | Exchange- Traded
Derivative Assets
Total gross derivatives	115	55
Derivative Liabilities
Total gross derivatives	66	19
Not designated as accounting hedges | Equity
Derivative Assets
Total gross derivatives	48,900	47,874
Derivative Liabilities
Total gross derivatives	49,934	50,640
Not designated as accounting hedges | Equity | Bilateral OTC
Derivative Assets
Total gross derivatives	26,395	24,590
Derivative Liabilities
Total gross derivatives	27,820	27,119
Not designated as accounting hedges | Equity | Cleared OTC
Derivative Assets
Total gross derivatives	0	0
Derivative Liabilities
Total gross derivatives	0	0
Not designated as accounting hedges | Equity | Exchange- Traded
Derivative Assets
Total gross derivatives	22,505	23,284
Derivative Liabilities
Total gross derivatives	22,114	23,521
Not designated as accounting hedges | Commodity and other
Derivative Assets
Total gross derivatives	11,270	12,472
Derivative Liabilities
Total gross derivatives	8,905	9,040
Not designated as accounting hedges | Commodity and other | Bilateral OTC
Derivative Assets
Total gross derivatives	8,797	10,538
Derivative Liabilities
Total gross derivatives	6,690	6,983
Not designated as accounting hedges | Commodity and other | Cleared OTC
Derivative Assets
Total gross derivatives	0	0
Derivative Liabilities
Total gross derivatives	0	0
Not designated as accounting hedges | Commodity and other | Exchange- Traded
Derivative Assets
Total gross derivatives	2,473	1,934
Derivative Liabilities
Total gross derivatives	$ 2,215	$ 2,057