FAIR VALUE MEASUREMENTS: (Details) - Fair value measured on a recurring basis - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 27, 2014
Fair value measurements
Cash and cash equivalents	$ 70,726	$ 100,108	$ 45,142
Available for sale securities	134,542	131,347	126,870
Trading securities	71,371	71,682	69,367
Total assets measured at fair value	272,730	300,461	239,764
Foreign currency forward contracts
Fair value measurements
Derivative instruments, net	(2,977)	(1,939)	(1,238)
Commodity futures contracts
Fair value measurements
Derivative instruments, net	(932)	(737)	(377)
Level 1
Fair value measurements
Cash and cash equivalents	70,726	100,108	45,142
Available for sale securities	2,453	2,446
Trading securities	71,371	71,682	69,367
Total assets measured at fair value	143,618	173,499	114,132
Level 1 | Commodity futures contracts
Fair value measurements
Derivative instruments, net	(932)	(737)	(377)
Level 2
Fair value measurements
Available for sale securities	132,089	128,901	126,870
Total assets measured at fair value	129,112	126,962	125,632
Level 2 | Foreign currency forward contracts
Fair value measurements
Derivative instruments, net	$ (2,977)	$ (1,939)	$ (1,238)