INVESTMENTS - Carrying Value of Non-marketable Equity Securities Measured Using the Measurement Alternative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Equity Securities without Readily Determinable Fair Value, Annual Amount [Abstract]
Measurement alternative—carrying value	$ 642,000,000		$ 642,000,000		$ 538,000,000
Measurement alternative—impairment losses	3,000,000	$ 3,000,000	8,000,000	$ 4,000,000
Measurement alternative—downward changes for observable prices	12,000,000	2,000,000	12,000,000	4,000,000
Measurement alternative—upward changes for observable prices	19,000,000	4,000,000	85,000,000	112,000,000
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Cumulative Amount [Abstract]
Measurement alternative—impairment losses	15,000,000		15,000,000
Measurement alternative—downward changes for observable prices	30,000,000		30,000,000
Measurement alternative—upward changes for observable prices	304,000,000		304,000,000
Non-marketable equity securities, impairment loss recognized in earnings	$ 0	$ 0	$ 0	$ 0