STOCK-BASED COMPENSATION - Stock Options (Details) - Stock Options - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock Options
Vesting period	5 years
Expiration period	10 years
Shares
Outstanding at the beginning of the period (in shares)	7,000,000	12,000,000	18,000,000
Granted (in shares)	397,350	0	0
Exercised (in shares)	2,000,000	5,000,000	5,000,000
Forfeited (in shares)	0	0	3,000,000
Forfeitures upon spin off (in shares)	0	0	0
Modification upon spin off (in shares)	0	0	2,000,000
Outstanding at the end of the period (in shares)	5,000,000	7,000,000	12,000,000
Option shares vested and expected to vest at the end of the period (in shares)	5,000,000	7,000,000	12,000,000
Option shares exercisable at the end of the period (in shares)	4,000,000	6,000,000	10,000,000
Weighted average exercise price
Outstanding at the beginning of the period (in dollars per share)	$ 15	$ 17	$ 21
Granted (in dollars per share)	34	26	26
Exercised (in dollars per share)	15	21	17
Forfeited (in dollars per share)	0	0	29
Forfeitures upon spin off (in dollars per share)	0	0	19
Outstanding at the end of the period (in dollars per share)	16	15	17
Option shares vested and expected to vest at the end of the period (in dollars per share)	16	15	17
Option shares exercisable at the end of the period (in dollars per share)	$ 13	$ 13	$ 18
Aggregate intrinsic value
Exercised shares	$ 47	$ 64	$ 50
Option shares vested and expected to vest at the end of the period	147	118	133
Option shares exercisable at the end of the period	$ 123	$ 102	$ 113
Weighted average remaining option term
Outstanding at the end of the period	4 years	4 years	3 years
Option shares vested and expected to vest at the end of the period	4 years	4 years	3 years
Option shares exercisable at the end of the period	3 years	3 years	3 years
Additional disclosures
Total unrecognized compensation expense	$ 7	$ 6	$ 6
Weighted average remaining vesting period	3 years	3 years	2 years