DERIVATIVES ACTIVITIES - Credit Derivatives (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) agency	Dec. 31, 2018 USD ($)
Credit Risk Derivatives
Fair values, Receivable	$ 10,684	$ 10,765
Fair values, Payable	11,485	10,351
Notionals, Protection purchased	757,539	795,649
Notionals, Protection sold	701,018	724,939
Fair value of derivative in liability position	35,000	33,000
Fair value of collateral already posted	$ 35,000	33,000
Number of rating agencies | agency	3
Additional collateral to be posted	$ 700
Collateral to be segregated	100
Aggregate cash obligations and collateral requirements	800
Purchased
Credit Risk Derivatives
Fair values, Receivable	3,686	5,126
Fair values, Payable	7,987	5,882
Sold
Credit Risk Derivatives
Fair values, Receivable	6,998	5,639
Fair values, Payable	3,498	4,469
Within 1 year
Credit Risk Derivatives
Fair values, Receivable	1,400	2,037
Fair values, Payable	1,874	2,063
Notionals, Protection purchased	217,434	251,994
Notionals, Protection sold	210,754	225,597
From 1 to 5 years
Credit Risk Derivatives
Fair values, Receivable	7,051	6,720
Fair values, Payable	7,448	6,414
Notionals, Protection purchased	450,084	493,096
Notionals, Protection sold	411,686	456,409
After 5 years
Credit Risk Derivatives
Fair values, Receivable	2,233	2,008
Fair values, Payable	2,163	1,874
Notionals, Protection purchased	90,021	50,559
Notionals, Protection sold	78,578	42,933
Investment grade
Credit Risk Derivatives
Fair values, Receivable	4,788	4,725
Fair values, Payable	5,032	4,544
Notionals, Protection purchased	597,069	637,790
Notionals, Protection sold	544,124	568,849
Non-investment grade
Credit Risk Derivatives
Fair values, Receivable	5,896	6,040
Fair values, Payable	6,453	5,807
Notionals, Protection purchased	160,470	157,859
Notionals, Protection sold	156,894	156,090
Credit default swaps and options
Credit Risk Derivatives
Fair values, Receivable	10,173	10,030
Fair values, Payable	10,514	9,755
Notionals, Protection purchased	733,530	771,865
Notionals, Protection sold	690,880	712,623
Total return swaps and other
Credit Risk Derivatives
Fair values, Receivable	511	735
Fair values, Payable	971	596
Notionals, Protection purchased	24,009	23,784
Notionals, Protection sold	10,138	12,316
Banks
Credit Risk Derivatives
Fair values, Receivable	4,855	4,785
Fair values, Payable	4,613	4,432
Notionals, Protection purchased	202,581	214,842
Notionals, Protection sold	213,437	218,273
Broker-dealers
Credit Risk Derivatives
Fair values, Receivable	1,776	1,706
Fair values, Payable	1,670	1,612
Notionals, Protection purchased	57,539	62,904
Notionals, Protection sold	68,978	63,014
Non-financial
Credit Risk Derivatives
Fair values, Receivable	80	64
Fair values, Payable	93	87
Notionals, Protection purchased	5,509	2,687
Notionals, Protection sold	2,801	1,192
Insurance and other financial institutions
Credit Risk Derivatives
Fair values, Receivable	3,973	4,210
Fair values, Payable	5,109	4,220
Notionals, Protection purchased	491,910	515,216
Notionals, Protection sold	415,802	442,460
Interest rate swaps
Credit Risk Derivatives
Cash proceeds received for assets derecognized	4,600	4,100
Fair value of derecognized assets	4,600	4,100
Fair value gross derivative assets	89	55
Trading derivatives, liability	$ 7	$ 9