POSTRETIREMENT BENEFIT PLANS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Principal pension plans
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	$ 254	$ 291	$ 543	$ 606
Prior service cost (credit) amortization	72	76	145	152
Expected return on plan assets	(849)	(836)	(1,698)	(1,670)
Interest cost on benefit obligations	712	735	1,429	1,469
Net actuarial loss (gain) amortization	697	612	1,407	1,224
Curtailment loss (gain)	0	(1)	43	(1)
Pension plans/Retiree benefit plans cost	886	877	1,869	1,780
Other pension plans
Defined Benefit Plan Disclosure [Line Items]
Threshold to be included in other pension plans (greater than)	50		50
Service cost for benefits earned	123	118	274	231
Prior service cost (credit) amortization	(1)	0	(2)	(1)
Expected return on plan assets	(301)	(259)	(595)	(522)
Interest cost on benefit obligations	145	168	287	340
Net actuarial loss (gain) amortization	107	65	210	129
Pension plans/Retiree benefit plans cost	73	92	174	177
Principal retiree benefit plans
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	26	27	52	52
Prior service cost (credit) amortization	(43)	(41)	(86)	(82)
Expected return on plan assets	(9)	(11)	(18)	(22)
Interest cost on benefit obligations	56	63	113	126
Net actuarial loss (gain) amortization	(20)	(14)	(41)	(27)
Curtailment loss (gain)	0	0	3	0
Pension plans/Retiree benefit plans cost	$ 10	$ 24	$ 23	$ 47