EMPLOYEE BENEFIT PLANS (Reconciliation of Changes in Plan Assets Benefit Obligations and Funded Status) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Funded Status:
Noncurrent liability	$ (2,444)	$ (1,884)
Pension Plan
Change in plan assets:
Fair value of plan assets at beginning of year	18,547	15,312
Actual return on plan assets	2,736	3,713
Company contributions	343	328
Benefits and expenses paid	(867)	(806)
Fair value of plan assets at end of year	20,759	18,547	$ 15,312
Change in benefit obligation:
Benefit obligation at beginning of year	20,525	17,407
Service cost for benefits earned	530	443	514
Interest cost	713	758	687
Actuarial loss	2,271	2,723
Plan amendments	0	0
Benefits and expenses paid	(867)	(806)
Benefit obligation at end of year	23,172	20,525	17,407
Funded Status:
Current liability	(3)	(14)
Noncurrent liability	(2,410)	(1,964)
Net (liability) asset at end of year	(2,413)	(1,978)
Accumulated benefit obligation	20,700	18,400
PBOP Plans
Change in plan assets:
Fair value of plan assets at beginning of year	2,678	2,258
Actual return on plan assets	379	474
Company contributions	26	29
Plan participant contribution	81	82
Benefits and expenses paid	(169)	(165)
Fair value of plan assets at end of year	2,995	2,678	2,258
Change in benefit obligation:
Benefit obligation at beginning of year	1,832	1,745
Service cost for benefits earned	61	56	66
Interest cost	63	76	69
Actuarial loss	(14)	22
Benefits and expenses paid	(149)	(150)
Federal subsidy on benefits paid	3	2
Plan participant contributions	80	81
Benefit obligation at end of year	1,876	1,832	$ 1,745
Funded Status:
Noncurrent asset	1,153	879
Noncurrent liability	(34)	(33)
Net (liability) asset at end of year	1,119	846
PBOP Plans | Postretirement Life Insurance Plan
Change in plan assets:
Fair value of plan assets at beginning of year	305
Fair value of plan assets at end of year	343	305
Change in benefit obligation:
Benefit obligation at beginning of year	337
Benefit obligation at end of year	$ 377	$ 337