Condensed Consolidated Statements of Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Cumulative Effect, Period of Adoption, Adjustment [Member] Common Stock [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] AOCI Attributable to Parent [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Parent [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Noncontrolling Interest [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Common Stock [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] AOCI Attributable to Parent [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Parent [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Noncontrolling Interest [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Cross Currency Interest Rate Contract [Member] Common Stock [Member]	Cross Currency Interest Rate Contract [Member] Additional Paid-in Capital [Member]	Cross Currency Interest Rate Contract [Member] Retained Earnings [Member]	Cross Currency Interest Rate Contract [Member] AOCI Attributable to Parent [Member]	Cross Currency Interest Rate Contract [Member] Parent [Member]	Cross Currency Interest Rate Contract [Member] Noncontrolling Interest [Member]	Cross Currency Interest Rate Contract [Member]	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, 2018	50,700																					50,700
Balance in Other comprehensive income (loss) beginning of period at Dec. 31, 2018	$ 0	$ 0	$ (58)	$ 0	$ (58)	$ 0	$ (58)	$ 51	$ 901,363	$ 422,164	$ (3,799)	$ 1,319,779	$ 125,259	$ 1,445,038								$ 51	$ 901,363	$ 422,222	$ (3,799)	$ 1,319,837	$ 125,259	$ 1,445,096
Stock-based compensation																						$ 0	2,360	0	0	2,360	0	2,360
Exercise of options by employees and directors (in shares)																						52
Exercise of options by employees and directors																						$ 0	0	0	0	0	0	0
Cash paid to noncontrolling interest																						0	0	0	0	0	(4,146)	(4,146)
Cash dividend declared																						0	0	(5,579)	0	(5,579)	0	(5,579)
Net income																						0	0	25,946	0	25,946	1,855	27,801
Change in foreign currency translation adjustments																						0	0	0	(1,026)	(1,026)	(322)	(1,348)
Change in respect of derivative instruments designated for cash flow hedge																						0	0	0	22	22	0	22
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment																						0	0	0	(1,145)	(1,145)	0	(1,145)
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																						0	0	0	(8)	(8)	0	(8)
Change in unrealized gains or losses in respect of a cross currency swap derivative instrument that qualifies as a cash flow hedge																						$ 0	0	0	22	22	0	22
Balance (in shares) at Mar. 31, 2019																						50,752
Balance in Other comprehensive income (loss) end of period at Mar. 31, 2019																						$ 51	903,723	442,531	(5,956)	1,340,349	122,646	1,462,995
Balance (in shares) at Dec. 31, 2018	50,700																					50,700
Balance in Other comprehensive income (loss) beginning of period at Dec. 31, 2018	$ 0	0	(58)	0	(58)	0	(58)	51	901,363	422,164	(3,799)	1,319,779	125,259	1,445,038								$ 51	901,363	422,222	(3,799)	1,319,837	125,259	1,445,096
Change in foreign currency translation adjustments																												(3,057)
Change in respect of derivative instruments designated for cash flow hedge																					$ 0
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment																												(4,699)
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																												(24)
Change in unrealized gains or losses in respect of a cross currency swap derivative instrument that qualifies as a cash flow hedge																					0
Balance (in shares) at Sep. 30, 2019																						50,993
Balance in Other comprehensive income (loss) end of period at Sep. 30, 2019																						$ 51	910,651	480,879	(10,848)	1,380,733	124,055	1,504,788
Balance (in shares) at Mar. 31, 2019																						50,752
Balance in Other comprehensive income (loss) beginning of period at Mar. 31, 2019																						$ 51	903,723	442,531	(5,956)	1,340,349	122,646	1,462,995
Stock-based compensation																						$ 0	2,643	0	0	2,643	0	2,643
Exercise of options by employees and directors (in shares)																						110
Exercise of options by employees and directors																						$ 0	0	0	0	0	0	0
Cash paid to noncontrolling interest																						0	0	0	0	0	(2,767)	(2,767)
Cash dividend declared																						0	0	(5,589)	0	(5,589)	0	(5,589)
Net income																						0	0	33,938	0	33,938	2,017	35,955
Change in foreign currency translation adjustments																						0	0	0	298	298	184	482
Change in respect of derivative instruments designated for cash flow hedge																						0	0	0	18	18	0	18
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment																						0	0	0	(2,087)	(2,087)	0	(2,087)
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																						0	0	0	(9)	(9)	0	(9)
Change in unrealized gains or losses in respect of a cross currency swap derivative instrument that qualifies as a cash flow hedge																						$ 0	0	0	18	18	0	18
Balance (in shares) at Jun. 30, 2019																						50,862
Balance in Other comprehensive income (loss) end of period at Jun. 30, 2019																						$ 51	906,366	470,880	(7,736)	1,369,561	122,080	1,491,641
Stock-based compensation																						$ 0	2,228	0	0	2,228	0	2,228
Exercise of options by employees and directors (in shares)																						131
Exercise of options by employees and directors																						$ 0	2,057	0	0	2,057	0	2,057
Cash paid to noncontrolling interest																						0	0	0	0	0	(1,326)	(1,326)
Cash dividend declared																						0	0	(5,606)	0	(5,606)	0	(5,606)
Net income																						0	0	15,605	0	15,605	(805)	14,800
Change in foreign currency translation adjustments																						0	0	0	(1,656)	(1,656)	(535)	(2,191)
Change in respect of derivative instruments designated for cash flow hedge																					0	0	0	0	18	18	0	18
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment																						0	0	0	(1,467)	(1,467)	0	(1,467)
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																						0	0	0	(7)	(7)	0	(7)
Increase in noncontrolling interest																						0	0	0	0	0	4,641	4,641
Change in unrealized gains or losses in respect of a cross currency swap derivative instrument that qualifies as a cash flow hedge																					0	$ 0	0	0	18	18	0	18
Balance (in shares) at Sep. 30, 2019																						50,993
Balance in Other comprehensive income (loss) end of period at Sep. 30, 2019																						$ 51	910,651	480,879	(10,848)	1,380,733	124,055	1,504,788
Balance (in shares) at Dec. 31, 2019	51,032																					51,032
Balance in Other comprehensive income (loss) beginning of period at Dec. 31, 2019	$ 0	0	(755)	0	(755)	0	(755)	51	913,150	487,118	(8,654)	1,391,665	122,990	1,514,655								$ 51	913,150	487,873	(8,654)	1,392,420	122,990	1,515,410
Stock-based compensation																						$ 0	1,989	0	0	1,989	0	1,989
Exercise of options by employees and directors (in shares)																						4
Exercise of options by employees and directors																						$ 0	0	0	0	0	0	0
Cash paid to noncontrolling interest																						0	0	0	0	0	(3,007)	(3,007)
Cash dividend declared																						0	0	(5,614)	0	(5,614)	0	(5,614)
Net income																						0	0	26,033	0	26,033	3,543	29,576
Change in foreign currency translation adjustments																						0	0	0	(258)	(258)	(387)	(645)
Change in respect of derivative instruments designated for cash flow hedge																						0	0	0	13	13	0	13
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment																						0	0	0	(4,755)	(4,755)	0	(4,755)
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																						0	0	0	(8)	(8)	0	(8)
Increase in noncontrolling interest																						0	0	0	0	0	1,447	1,447
Change in unrealized gains or losses in respect of a cross currency swap derivative instrument that qualifies as a cash flow hedge																						$ 0	0	0	13	13	0	13
Balance (in shares) at Mar. 31, 2020																						51,036
Balance in Other comprehensive income (loss) end of period at Mar. 31, 2020																						$ 51	915,139	507,537	(13,662)	1,409,065	124,586	1,533,651
Balance (in shares) at Dec. 31, 2019	51,032																					51,032
Balance in Other comprehensive income (loss) beginning of period at Dec. 31, 2019	$ 0	$ 0	$ (755)	$ 0	$ (755)	$ 0	$ (755)	$ 51	$ 913,150	$ 487,118	$ (8,654)	$ 1,391,665	$ 122,990	$ 1,514,655								$ 51	913,150	487,873	(8,654)	1,392,420	122,990	1,515,410
Change in foreign currency translation adjustments																												1,597
Change in respect of derivative instruments designated for cash flow hedge																					(3,548)
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment																												(4,461)
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																												(19)
Change in unrealized gains or losses in respect of a cross currency swap derivative instrument that qualifies as a cash flow hedge																					(3,548)
Balance (in shares) at Sep. 30, 2020																						51,069
Balance in Other comprehensive income (loss) end of period at Sep. 30, 2020																						$ 51	920,210	534,984	(15,503)	1,439,742	132,061	1,571,803
Balance (in shares) at Mar. 31, 2020																						51,036
Balance in Other comprehensive income (loss) beginning of period at Mar. 31, 2020																						$ 51	915,139	507,537	(13,662)	1,409,065	124,586	1,533,651
Stock-based compensation																						$ 0	2,264	0	0	2,264	0	2,264
Exercise of options by employees and directors (in shares)																						31
Exercise of options by employees and directors																						$ 0	0	0	0	0	0	0
Cash dividend declared																						0	0	(5,719)	0	(5,719)	0	(5,719)
Net income																						0	0	23,046	0	23,046	1,982	25,028
Change in foreign currency translation adjustments																						0	0	0	382	382	539	921
Change in respect of derivative instruments designated for cash flow hedge																						0	0	0	17	17	0	17
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment																						0	0	0	(653)	(653)	0	(653)
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																						0	0	0	(5)	(5)	0	(5)
Increase in noncontrolling interest																						0	0	0	0	0	1,307	1,307
Change in unrealized gains or losses in respect of a cross currency swap derivative instrument that qualifies as a cash flow hedge																						$ 0	0	0	17	17	0	17
Balance (in shares) at Jun. 30, 2020																						51,067
Balance in Other comprehensive income (loss) end of period at Jun. 30, 2020																						$ 51	917,403	524,864	(13,921)	1,428,397	128,414	1,556,811
Stock-based compensation																						$ 0	2,807	0	0	2,807	0	2,807
Exercise of options by employees and directors (in shares)																						2
Exercise of options by employees and directors																						$ 0	0	0	0	0	0	0
Cash paid to noncontrolling interest																						0	0	0	0	0	(3,749)	(3,749)
Cash dividend declared																						0	0	(5,559)	0	(5,559)	0	(5,559)
Net income																						0	0	15,679	0	15,679	7,064	22,743
Change in foreign currency translation adjustments																						0	0	0	989	989	332	1,321
Change in respect of derivative instruments designated for cash flow hedge															$ 0	$ 0	$ 0	$ (3,548)	$ (3,548)	$ 0	(3,548)	0	0	0	36	36	0	36
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment																						0	0	0	947	947	0	947
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																						0	0	0	(6)	(6)	0	(6)
Change in unrealized gains or losses in respect of a cross currency swap derivative instrument that qualifies as a cash flow hedge															$ 0	$ 0	$ 0	$ (3,548)	$ (3,548)	$ 0	$ (3,548)	$ 0	0	0	36	36	0	36
Balance (in shares) at Sep. 30, 2020																						51,069
Balance in Other comprehensive income (loss) end of period at Sep. 30, 2020																						$ 51	$ 920,210	$ 534,984	$ (15,503)	$ 1,439,742	$ 132,061	$ 1,571,803