INVESTMENTS - Carrying Value of Non-marketable Equity Securities Measured Using the Measurement Alternative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Equity Securities without Readily Determinable Fair Value, Annual Amount [Abstract]
Measurement alternative - carrying value	$ 962,000,000	$ 700,000,000
Measurement alternative - impairment losses	56,000,000	9,000,000
Measurement alternative - downward changes for observable prices	19,000,000	16,000,000
Measurement alternative - upward changes for observable prices	144,000,000	123,000,000
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Cumulative Amount [Abstract]
Measurement alternative - impairment losses	68,000,000
Measurement alternative - downward changes for observable prices	53,000,000
Measurement alternative - upward changes for observable prices	486,000,000
Impairment loss recognized in earnings for non-marketable equity securities carried at cost	$ 0	$ 0