FAIR VALUE MEASUREMENTS (Schedule of Unrealized Gains Losses Related to Available-for-sale Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 2,180	$ 2,011
Total Unrealized Gains	2,033	1,698
Total Unrealized Losses	(4)	(6)
Total Fair Value	4,209	3,703
Amount primarily related to deferred taxes on appreciation of investment value	671	530
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	27	6
Total Unrealized Gains	0	0
Total Unrealized Losses	0	0
Total Fair Value	27	6
Global equity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	543	500
Total Unrealized Gains	1,881	1,609
Total Unrealized Losses	(1)	(2)
Total Fair Value	2,423	2,107
Fixed-income securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,610	1,505
Total Unrealized Gains	152	89
Total Unrealized Losses	(3)	(4)
Total Fair Value	$ 1,759	$ 1,590