PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Net Periodic Benefit Cost and Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income for All Significant Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 506	$ 463	$ 484
Interest cost	883	846	975
Expected return on plan assets	(1,548)	(1,447)	(1,382)
Amortization of prior service credit	(25)	(24)	(28)
Amortization of unrecognized (gain) loss	638	587	706
Curtailment/settlement/other 1	683	(36)	0
Net periodic benefit cost	1,137	389	755
Net (gain) loss	845	1,954	(127)
Prior service cost	14	0	63
Amortization of prior service (cost) credit	25	24	28
Amortization of unrecognized gain (loss)	(638)	(587)	(706)
Settlement loss 2	(687)	0	0
Total recognized in other comprehensive (income) loss	(441)	1,391	(742)
Total recognized in net periodic benefit cost and other comprehensive (income) loss	696	1,780	13
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	14	13	14
Interest cost	54	52	59
Expected return on plan assets	0	0	0
Amortization of prior service credit	0	(3)	(2)
Amortization of unrecognized (gain) loss	(6)	(7)	(11)
Curtailment/settlement/other 1	0	0	0
Net periodic benefit cost	62	55	60
Net (gain) loss	(199)	14	11
Prior service cost	0	0	0
Amortization of prior service (cost) credit	0	3	2
Amortization of unrecognized gain (loss)	6	7	11
Settlement loss 2	0	0	0
Total recognized in other comprehensive (income) loss	(193)	24	24
Total recognized in net periodic benefit cost and other comprehensive (income) loss	$ (131)	$ 79	$ 84