STOCK-BASED COMPENSATION - Stock Option Shares Outstanding and Exercisable (Details) shares in Millions	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Stock-based compensation
Exercise price range, low end of range (in dollars per share)	$ 7
Exercise price range, high end of range (in dollars per share)	$ 43
Option Shares Outstanding, Number of shares (in shares) | shares	4
Option Shares Outstanding, Weighted Average Remaining Option Term	5 years
Option Shares Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 21
Option Shares Exercisable, Number of Shares (in shares) | shares	3
Option Shares Exercisable, Weighted Average Exercise price (in dollars per share)	$ 16
Range One
Stock-based compensation
Exercise price range, low end of range (in dollars per share)	7
Exercise price range, high end of range (in dollars per share)	$ 13
Option Shares Outstanding, Number of shares (in shares) | shares	1
Option Shares Outstanding, Weighted Average Remaining Option Term	2 years
Option Shares Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 11
Option Shares Exercisable, Number of Shares (in shares) | shares	1
Option Shares Exercisable, Weighted Average Exercise price (in dollars per share)	$ 11
Range Two
Stock-based compensation
Exercise price range, low end of range (in dollars per share)	17
Exercise price range, high end of range (in dollars per share)	$ 26
Option Shares Outstanding, Number of shares (in shares) | shares	2
Option Shares Outstanding, Weighted Average Remaining Option Term	5 years
Option Shares Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 21
Option Shares Exercisable, Number of Shares (in shares) | shares	2
Option Shares Exercisable, Weighted Average Exercise price (in dollars per share)	$ 20
Range Three
Stock-based compensation
Exercise price range, low end of range (in dollars per share)	30
Exercise price range, high end of range (in dollars per share)	$ 43
Option Shares Outstanding, Number of shares (in shares) | shares	1
Option Shares Outstanding, Weighted Average Remaining Option Term	9 years
Option Shares Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 38
Option Shares Exercisable, Number of Shares (in shares) | shares	0
Option Shares Exercisable, Weighted Average Exercise price (in dollars per share)	$ 34