STOCK-BASED COMPENSATION - Stock Options (Details) - Stock Options - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock Options
Vesting period	5 years
Expiration period	10 years
Shares
Outstanding at the beginning of the period (in shares)	4,000,000	5,000,000	7,000,000
Granted (in shares)	561,280	0	0
Exercised (in shares)	2,000,000	1,000,000	2,000,000
Forfeited (in shares)	108,086	0	0
Outstanding at the end of the period (in shares)	3,000,000	4,000,000	5,000,000
Option shares vested and expected to vest at the end of the period (in shares)	3,000,000	4,000,000	5,000,000
Option shares exercisable at the end of the period (in shares)	2,000,000	3,000,000	4,000,000
Weighted average exercise price
Outstanding at the beginning of the period (in dollars per share)	$ 21	$ 16	$ 15
Granted (in dollars per share)	36	42	34
Exercised (in dollars per share)	13	11	15
Forfeited (in dollars per share)	34	31	0
Outstanding at the end of the period (in dollars per share)	27	21	16
Option shares vested and expected to vest at the end of the period (in dollars per share)	27	21	16
Option shares exercisable at the end of the period (in dollars per share)	$ 21	$ 16	$ 13
Aggregate intrinsic value
Exercised shares	$ 33	$ 55	$ 47
Option shares vested and expected to vest at the end of the period	63	36	147
Option shares exercisable at the end of the period	$ 47	$ 34	$ 123
Weighted average remaining option term
Outstanding at the end of the period	6 years	5 years	4 years
Option shares vested and expected to vest at the end of the period	6 years	5 years	4 years
Option shares exercisable at the end of the period	4 years	4 years	3 years
Additional disclosures
Total unrecognized compensation expense	$ 9	$ 8	$ 7
Remaining weighted average vesting period	3 years	3 years	3 years