PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 112	$ 133
Interest cost	241	218
Expected return on plan assets	(417)	(406)
Amortization of prior service credit	(6)	(6)
Amortization of net (gain) loss	132	171
Net periodic benefit cost	62	110
Other Postretirement Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	3
Interest cost	14	11
Amortization of net (gain) loss	(6)	(6)
Net periodic benefit cost	$ 10	$ 8