DERIVATIVES ACTIVITIES - Fair Value Hedges (Details) - Other revenue - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gain (loss) on fair value hedges
Gain (loss) on the derivatives in designated and qualifying fair value hedges	$ (1,732)	$ (1,986)	$ 509
Gain (loss) on the hedged item in designated and qualifying fair value hedges	1,840	2,031	(501)
Hedge ineffectiveness recognized in earnings on designated and qualifying fair value hedges	18	(80)	(70)
Net gain (loss) excluded from assessment of the effectiveness of fair value hedges	90	125	78
Interest rate contracts
Gain (loss) on fair value hedges
Gain (loss) on the derivatives in designated and qualifying fair value hedges	(891)	(753)	(847)
Gain (loss) on the hedged item in designated and qualifying fair value hedges	853	668	792
Hedge ineffectiveness recognized in earnings on designated and qualifying fair value hedges	(31)	(84)	(47)
Net gain (loss) excluded from assessment of the effectiveness of fair value hedges	(7)	(1)	(8)
Foreign exchange contracts
Gain (loss) on fair value hedges
Gain (loss) on the derivatives in designated and qualifying fair value hedges	(824)	(1,415)	1,315
Gain (loss) on the hedged item in designated and qualifying fair value hedges	969	1,573	(1,258)
Hedge ineffectiveness recognized in earnings on designated and qualifying fair value hedges	49	4	(23)
Net gain (loss) excluded from assessment of the effectiveness of fair value hedges	96	154	80
Commodity and other contract options
Gain (loss) on fair value hedges
Gain (loss) on the derivatives in designated and qualifying fair value hedges	(17)	182	41
Gain (loss) on the hedged item in designated and qualifying fair value hedges	18	(210)	(35)
Net gain (loss) excluded from assessment of the effectiveness of fair value hedges	$ 1	$ (28)	$ 6