FAIR VALUE MEASUREMENTS (Schedule of Unrealized Gains (Losses) Related to Available-for-Sale Investments) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,842	$ 1,799
Total Unrealized Gains	1,448	1,514
Total Unrealized Losses	(26)	(10)
Total Fair Value	3,264	3,303
Amount primarily related to deferred taxes on appreciation of investment value	436	440
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	22	23
Total Unrealized Gains	0	0
Total Unrealized Losses	0	0
Total Fair Value	22	23
Global equity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	482	524
Total Unrealized Gains	1,412	1,463
Total Unrealized Losses	(3)	(2)
Total Fair Value	1,891	1,985
Fixed-income securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,338	1,252
Total Unrealized Gains	36	51
Total Unrealized Losses	(23)	(8)
Total Fair Value	$ 1,351	$ 1,295