DERIVATIVES - Credit Derivatives (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($) agency	Dec. 31, 2018 USD ($)
Credit Risk Derivatives
Fair values, Receivable	$ 10,987	$ 10,765
Fair values, Payable	11,920	10,351
Notionals, Protection purchased	747,129	795,649
Notionals, Protection sold	666,733	724,939
Fair value of derivative in liability position	30,000	33,000
Fair value of collateral already posted	$ 29,000	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	3,931	5,126
Fair values, Payable	8,377	5,882
Sold
Credit Risk Derivatives
Fair values, Receivable	7,056	5,639
Fair values, Payable	3,543	4,469
Within 1 year
Credit Risk Derivatives
Fair values, Receivable	1,733	2,037
Fair values, Payable	2,493	2,063
Notionals, Protection purchased	240,625	251,994
Notionals, Protection sold	206,633	225,597
From 1 to 5 years
Credit Risk Derivatives
Fair values, Receivable	7,542	6,720
Fair values, Payable	7,760	6,414
Notionals, Protection purchased	452,460	493,096
Notionals, Protection sold	417,738	456,409
After 5 years
Credit Risk Derivatives
Fair values, Receivable	1,712	2,008
Fair values, Payable	1,667	1,874
Notionals, Protection purchased	54,044	50,559
Notionals, Protection sold	42,362	42,933
Investment grade
Credit Risk Derivatives
Fair values, Receivable	5,027	4,725
Fair values, Payable	5,281	4,544
Notionals, Protection purchased	590,084	637,790
Notionals, Protection sold	515,070	568,849
Non-investment grade
Credit Risk Derivatives
Fair values, Receivable	5,960	6,040
Fair values, Payable	6,639	5,807
Notionals, Protection purchased	157,045	157,859
Notionals, Protection sold	151,663	156,090
Credit default swaps and options
Credit Risk Derivatives
Fair values, Receivable	10,384	10,030
Fair values, Payable	10,526	9,755
Notionals, Protection purchased	720,153	771,865
Notionals, Protection sold	655,896	712,623
Total return swaps and other
Credit Risk Derivatives
Fair values, Receivable	603	735
Fair values, Payable	1,394	596
Notionals, Protection purchased	26,976	23,784
Notionals, Protection sold	10,837	12,316
Banks
Credit Risk Derivatives
Fair values, Receivable	4,748	4,785
Fair values, Payable	4,551	4,432
Notionals, Protection purchased	206,498	214,842
Notionals, Protection sold	204,392	218,273
Broker-dealers
Credit Risk Derivatives
Fair values, Receivable	1,535	1,706
Fair values, Payable	1,470	1,612
Notionals, Protection purchased	59,717	62,904
Notionals, Protection sold	61,717	63,014
Non-financial
Credit Risk Derivatives
Fair values, Receivable	77	64
Fair values, Payable	119	87
Notionals, Protection purchased	2,323	2,687
Notionals, Protection sold	1,567	1,192
Insurance and other financial institutions
Credit Risk Derivatives
Fair values, Receivable	4,627	4,210
Fair values, Payable	5,780	4,220
Notionals, Protection purchased	478,591	515,216
Notionals, Protection sold	399,057	442,460
Interest rate swaps
Credit Risk Derivatives
Cash proceeds received for assets derecognized	6,000	4,100
Fair value of derecognized assets	6,100	4,100
Fair value gross derivative assets	90	55
Trading derivatives, liability	$ 57	$ 9