FAIR VALUE MEASUREMENTS (Schedule of Unrealized Gains Losses Related to Available-for-sale Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,885	$ 1,799
Total Unrealized Gains	1,276	1,514
Total Unrealized Losses	(23)	(10)
Total Fair Value	3,138	3,303
Amount primarily related to deferred taxes on appreciation of investment value	408	440
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	29	23
Total Unrealized Gains	0	0
Total Unrealized Losses	0	0
Total Fair Value	29	23
Global equity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	568	524
Total Unrealized Gains	1,246	1,463
Total Unrealized Losses	(5)	(2)
Total Fair Value	1,809	1,985
Fixed-income securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,288	1,252
Total Unrealized Gains	30	51
Total Unrealized Losses	(18)	(8)
Total Fair Value	$ 1,300	$ 1,295