EMPLOYEE BENEFIT PLANS (Reconciliation of Changes in Plan Assets Benefit Obligations and Funded Status) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Funded Status:
Noncurrent liability	$ (2,119)	$ (2,128)
Pension Plan
Change in plan assets:
Fair value of plan assets at beginning of year	16,652	14,729
Actual return on plan assets	(923)	2,380
Company contributions	334	335
Benefits and expenses paid	(751)	(792)
Fair value of plan assets at end of year	15,312	16,652	$ 14,729
Change in benefit obligation:
Benefit obligation at beginning of year	18,757	17,305
Service cost for benefits earned	514	472	453
Interest cost	687	714	715
Actuarial (gain) loss	(1,800)	1,048
Plan amendments	0	10
Benefits and expenses paid	(751)	(792)
Benefit obligation at end of year	17,407	18,757	17,305
Funded Status:
Current liability	(8)	(7)
Noncurrent liability	(2,087)	(2,098)
Net assets (liabilities) at end of year	(2,095)	(2,105)
Accumulated benefit obligation	15,800	16,800
PBOP Plans
Change in plan assets:
Fair value of plan assets at beginning of year	2,420	2,173
Actual return on plan assets	(108)	298
Company contributions	31	33
Plan participant contribution	81	87
Benefits and expenses paid	(166)	(171)
Fair value of plan assets at end of year	2,258	2,420	2,173
Change in benefit obligation:
Benefit obligation at beginning of year	1,897	1,877
Service cost for benefits earned	66	59	52
Interest cost	69	77	76
Actuarial (gain) loss	(221)	(49)
Benefits and expenses paid	(150)	(157)
Federal subsidy on benefits paid	3	3
Plan participant contributions	81	87
Benefit obligation at end of year	1,745	1,897	$ 1,877
Funded Status:
Noncurrent asset	545	553
Noncurrent liability	(32)	(30)
Net assets (liabilities) at end of year	$ 513	$ 523