FINANCIAL INSTRUMENTS Schedule of Other Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost	$ 126,500	$ 145,089
Unrealized gains	25,632	11,000
Unrealized losses	0	(26)
Fair value	152,132	156,063
Commodities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost	101,184	130,671
Unrealized gains	20,318	6,625
Unrealized losses	0	0
Fair value	121,502	137,296
Private and unlisted equity securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost	25,316	14,418
Unrealized gains	5,314	4,375
Unrealized losses	0	(26)
Fair value	$ 30,630	$ 18,767