DERIVATIVES ACTIVITIES - Credit Derivatives (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($) agency	Dec. 31, 2017 USD ($)
Credit Risk Derivatives
Fair values, Receivable	$ 11,566	$ 20,534
Fair values, Payable	11,693	21,533
Notionals, Protection purchased	793,792	777,713
Notionals, Protection sold	723,060	735,142
Fair value of derivative in liability position	37,000	29,000
Fair value of collateral already posted	$ 36,000	28,000
Number of rating agencies | agency	3
Additional collateral to be posted	$ 1,400
Collateral to be segregated	200
Aggregate cash obligations and collateral requirements	1,600
Purchased
Credit Risk Derivatives
Fair values, Receivable	3,657	3,195
Fair values, Payable	8,476	3,147
Sold
Credit Risk Derivatives
Fair values, Receivable	7,909	17,339
Fair values, Payable	3,217	18,386
Within 1 year
Credit Risk Derivatives
Fair values, Receivable	1,442	2,477
Fair values, Payable	1,680	2,914
Notionals, Protection purchased	232,670	231,878
Notionals, Protection sold	204,358	218,097
From 1 to 5 years
Credit Risk Derivatives
Fair values, Receivable	8,083	16,098
Fair values, Payable	7,855	16,435
Notionals, Protection purchased	472,276	498,606
Notionals, Protection sold	439,089	476,345
After 5 years
Credit Risk Derivatives
Fair values, Receivable	2,041	1,959
Fair values, Payable	2,158	2,184
Notionals, Protection purchased	88,846	47,229
Notionals, Protection sold	79,613	40,700
Investment grade
Credit Risk Derivatives
Fair values, Receivable	5,180	10,473
Fair values, Payable	5,014	10,616
Notionals, Protection purchased	616,595	588,324
Notionals, Protection sold	552,452	557,987
Non-investment grade
Credit Risk Derivatives
Fair values, Receivable	6,386	10,061
Fair values, Payable	6,679	10,917
Notionals, Protection purchased	177,197	189,389
Notionals, Protection sold	170,608	177,155
Credit default swaps and options
Credit Risk Derivatives
Fair values, Receivable	10,997	20,251
Fair values, Payable	11,168	20,554
Notionals, Protection purchased	771,239	754,114
Notionals, Protection sold	712,451	724,228
Total return swaps and other
Credit Risk Derivatives
Fair values, Receivable	569	283
Fair values, Payable	525	979
Notionals, Protection purchased	22,553	23,599
Notionals, Protection sold	10,609	10,914
Banks
Credit Risk Derivatives
Fair values, Receivable	5,366	7,471
Fair values, Payable	5,097	6,669
Notionals, Protection purchased	222,802	264,414
Notionals, Protection sold	234,338	273,711
Broker-dealers
Credit Risk Derivatives
Fair values, Receivable	1,826	2,325
Fair values, Payable	1,661	2,285
Notionals, Protection purchased	66,676	73,273
Notionals, Protection sold	67,833	83,229
Non-financial
Credit Risk Derivatives
Fair values, Receivable	65	70
Fair values, Payable	90	91
Notionals, Protection purchased	2,823	1,288
Notionals, Protection sold	4,247	1,140
Insurance and other financial institutions
Credit Risk Derivatives
Fair values, Receivable	4,309	10,668
Fair values, Payable	4,845	12,488
Notionals, Protection purchased	501,491	438,738
Notionals, Protection sold	416,642	377,062
Interest rate swaps
Credit Risk Derivatives
Cash proceeds received for assets derecognized	3,300	3,000
Fair value of derecognized assets	3,200	3,100
Fair value gross derivative assets	24	89
Trading derivatives, liability	$ 31	$ 15