FAIR VALUE MEASUREMENTS (Schedule of Unrealized Gains (Losses) Related to Available-for-Sale Investments) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,861	$ 1,799
Total Unrealized Gains	1,541	1,514
Total Unrealized Losses	(30)	(10)
Total Fair Value	3,372	3,303
Amount primarily related to deferred taxes on appreciation of investment value	455	440
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14	23
Total Unrealized Gains	0	0
Total Unrealized Losses	0	0
Total Fair Value	14	23
Global equity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	478	524
Total Unrealized Gains	1,513	1,463
Total Unrealized Losses	(2)	(2)
Total Fair Value	1,989	1,985
Fixed-income securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,369	1,252
Total Unrealized Gains	28	51
Total Unrealized Losses	(28)	(8)
Total Fair Value	$ 1,369	$ 1,295