INVESTMENTS - Carrying Value of Non-marketable Equity Securities Measured Using the Measurement Alternative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Investments, Debt and Equity Securities [Abstract]
Measurement alternative, balance at March 31, 2018	$ 401
Measurement alternative—impairment losses	1
Measurement alternative—downward changes for observable prices	2
Measurement alternative—upward changes for observable prices	$ 123