RETIREMENT AND DEFERRED COMPENSATION PLANS - Components of Net Periodic Cost and Underlying Weighted Average Actuarial Assumptions Used for Pension and Postretirement Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost for the Years Ended December 31
Salary increases	4.30%	4.70%	4.70%
Expected return on assets	2.20%	2.80%	2.90%
Pension Benefits
Components of Net Periodic Benefit Cost
Service cost	$ 3	$ 3	$ 4
Interest cost	4	5	5
Expected return on assets	(5)	(5)	(7)
Amortization of gain	0	0	0
Settlement loss	0	0	1
Net periodic benefit cost	$ 2	$ 3	$ 3
Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost for the Years Ended December 31
Discount rate	2.10%	2.90%	2.60%
Postretirement Benefits
Components of Net Periodic Benefit Cost
Service cost	$ 1	$ 2	$ 2
Interest cost	0	1	1
Expected return on assets	0	0	0
Amortization of gain	(1)	(1)	0
Settlement loss	0	0	0
Net periodic benefit cost	$ 0	$ 2	$ 3
Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost for the Years Ended December 31
Discount rate	3.00%	4.13%	3.44%
Healthcare cost trend
Initial	6.25%	6.50%	6.75%
Ultimate in 2025	5.00%	5.00%	5.00%