SHAREHOLDERS' EQUITY - Summary of Stock Repurchase Activity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2019
Stock Repurchase [Roll Forward]
Number of shares repurchased (in shares)			11,633,731		11,633,731
Repurchase of common stock (in shares)	0	0	0	0
Cost of Shares Repurchased	$ 127	$ 109	$ 106	$ 2
Number of shares repurchased (in shares)	15,281,979				15,281,979
Treasury Stock
Stock Repurchase [Roll Forward]
Number of shares repurchased (in shares)			11,687,774		11,687,774
Cost of Shares Repurchased			$ 793		$ 793
Average price paid per share (in usd per share)			$ 67.85		$ 67.85
Repurchase of common stock (in shares)					3,667,175
Cost of Shares Repurchased	$ 127	$ 109	$ 106	$ 2	$ 342
Average price paid per share (in usd per share)					$ 93.24
Number of shares repurchased (in shares)	15,354,949				15,354,949
Cost of Shares Repurchased	$ 1,135				$ 1,135
Average price paid per share (in usd per share)	$ 73.91				$ 73.91