Consolidated Statements of Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Parent [Member]	Noncontrolling Interest [Member]	Total
Balance (in shares) at Dec. 31, 2015	49,107
Balance at Dec. 31, 2015	$ 49	$ 849,223	$ 148,396	$ (7,667)	$ 990,001	$ 93,873	$ 1,083,874
Stock-based compensation		3,383			3,383		3,383
Exercise of options by employees and directors (in shares)	528
Exercise of options by employees and directors	$ 1	7,249			7,250		7,250
Cash paid to noncontrolling interest						(10,622)	(10,622)
Cash dividend declared			(22,469)		(22,469)		(22,469)
Increase in noncontrolling interest in Guadeloupe						8,272	8,272
Net income			65,700		65,700	4,390	70,090
Loss in respect of derivative instruments designated for cash flow hedge				65	65		65
Change in unrealized gains or losses in respect of the Company's share in derivatives instruments of unconsolidated investment				(3,829)	(3,829)		(3,829)
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge				(72)	(72)		(72)
Currency translation adjustment
Balance (in shares) at Sep. 30, 2016	49,635
Balance at Sep. 30, 2016	$ 50	859,855	191,627	(11,503)	1,040,029	95,913	1,135,942
Balance (in shares) at Dec. 31, 2016	49,667
Balance at Dec. 31, 2016	$ 50	869,463	216,644	(7,732)	1,078,425	91,582	1,170,007
Stock-based compensation		7,204			7,204		7,204
Exercise of options by employees and directors (in shares)	930
Exercise of options by employees and directors	$ 1	16,382			16,383		16,383
Cash paid to noncontrolling interest						(18,032)	(18,032)
Cash dividend declared			(16,612)		(16,612)		(16,612)
Net income			89,529		89,529	10,154	99,683
Loss in respect of derivative instruments designated for cash flow hedge				62	62		62
Change in unrealized gains or losses in respect of the Company's share in derivatives instruments of unconsolidated investment				271	271		271
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge				(57)	(57)		(57)
Buyout of Class B membership in ORTP		2,956			2,956	(6,964)	(4,008)
Currency translation adjustment				1,822	1,822	722	2,544
Balance (in shares) at Sep. 30, 2017	50,597
Balance at Sep. 30, 2017	$ 51	$ 896,005	$ 289,561	$ (5,634)	$ 1,179,983	$ 77,462	$ 1,257,445