INVESTMENTS - Carrying Value of Non-marketable Equity Securities Measured Using the Measurement Alternative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Equity Securities without Readily Determinable Fair Value, Annual Amount [Abstract]
Measurement alternative—carrying value	$ 1,392		$ 1,392		$ 962
Measurement alternative—impairment losses	9	$ 2	13	$ 55
Measurement alternative—downward changes for observable prices	0	0	0	19
Measurement alternative—upward changes for observable prices	86	40	382	82
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Cumulative Amount [Abstract]
Measurement alternative—impairment losses	76		76
Measurement alternative—downward changes for observable prices	53		53
Measurement alternative—upward changes for observable prices	861		861
Non-marketable equity securities, impairment loss recognized in earnings	$ 0	$ 0	$ 0	$ 0