EMPLOYEE BENEFIT PLANS - Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock-based compensation expense [Line Items]
Total stock-based compensation expense	$ 181	$ 163	$ 137
Tax benefit recognized	(29)	(35)	(21)
Stock-based compensation expense, net of tax	152	128	116
Restricted stock
Stock-based compensation expense [Line Items]
Total stock-based compensation expense	171	152	124
Stock options
Stock-based compensation expense [Line Items]
Total stock-based compensation expense	$ 10	$ 11	$ 13