EMPLOYEE BENEFITS - Changes in the Fair Value of Pension Plan Assets, Projected Benefit Obligation, Funded Status, and Accumulated Benefit Obligation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Qualified Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets as of January 1	$ 1,050	$ 1,139
Actual return on plan assets	259	(81)
Employer contributions	0	50
Benefits and administrative expenses paid	(63)	(58)
Fair value of plan assets as of December 31	1,246	1,050
Projected benefit obligation	1,075	972
Pension asset (obligation)	171	78
Accumulated benefit obligation	1,075	972
Non-Qualified Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets as of January 1	0	0
Actual return on plan assets	0	0
Employer contributions	8	8
Benefits and administrative expenses paid	(8)	(8)
Fair value of plan assets as of December 31	0	0
Projected benefit obligation	102	95
Pension asset (obligation)	(102)	(95)
Accumulated benefit obligation	$ 102	$ 95