EMPLOYEE BENEFIT PLANS (Reconciliation of Changes in Plan Assets Benefit Obligations and Funded Status) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Funded Status:
Noncurrent liability	$ (1,884)	$ (2,119)
Pension Plan
Change in plan assets:
Fair value of plan assets at beginning of year	15,312	16,652
Actual return on plan assets	3,713	(923)
Company contributions	328	334
Benefits and expenses paid	(806)	(751)
Fair value of plan assets at end of year	18,547	15,312	$ 16,652
Change in benefit obligation:
Benefit obligation at beginning of year	17,407	18,757
Service cost for benefits earned	443	514	472
Interest cost	758	687	714
Actuarial (gain) loss	2,723	(1,800)
Plan amendments	0	0
Benefits and expenses paid	(806)	(751)
Benefit obligation at end of year	20,525	17,407	18,757
Funded Status:
Current liability	(14)	(8)
Noncurrent liability	(1,964)	(2,087)
Net (liability) asset at end of year	(1,978)	(2,095)
Accumulated benefit obligation	18,400	15,800
PBOP Plans
Change in plan assets:
Fair value of plan assets at beginning of year	2,258	2,420
Actual return on plan assets	474	(108)
Company contributions	29	31
Plan participant contribution	82	81
Benefits and expenses paid	(165)	(166)
Fair value of plan assets at end of year	2,678	2,258	2,420
Change in benefit obligation:
Benefit obligation at beginning of year	1,745	1,897
Service cost for benefits earned	56	66	59
Interest cost	76	69	77
Actuarial (gain) loss	22	(221)
Benefits and expenses paid	(150)	(150)
Federal subsidy on benefits paid	2	3
Plan participant contributions	81	81
Benefit obligation at end of year	1,832	1,745	$ 1,897
Funded Status:
Noncurrent asset	879	545
Noncurrent liability	(33)	(32)
Net (liability) asset at end of year	$ 846	$ 513