Consolidated Statements of Equity - USD ($) $ in Thousands		Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Noncontrolling Interests' Equity [Member]
Beginning Balance at Dec. 31, 2015		$ 558,384	$ 25,709	$ 144,601	$ (68,446)	$ (125,088)	$ 580,208	$ 1,400
Issuance of common stock under stock option plan		4,017	168	3,849
Purchase of common stock		(2,408)			(2,408)
Stock-based and deferred compensation		9,526	18	9,592	(84)
Net income		86,198					86,191	7
Other comprehensive income		(2,472)				(2,377)		(95)
Cash dividends paid:
Common stock		(17,329)					(17,329)
Ending Balance at Dec. 31, 2016		635,916	25,895	158,042	(70,938)	(127,465)	649,070	1,312
Issuance of common stock under stock option plan		3,370	104	3,266
Purchase of common stock		(6,000)			(6,000)
Stock-based and deferred compensation		7,549	72	9,100	(1,623)
Net income		91,547					91,578	(31)
Other comprehensive income		27,981				27,902		79
Cash dividends paid:
Common stock		(18,907)					(18,907)
Payment of cash dividends to noncontrolling interest		(542)						(542)
Ending Balance at Dec. 31, 2017		740,914	26,071	170,408	(78,561)	(99,563)	721,741	818
Issuance of common stock under stock option plan		4,163	97	4,066
Purchase of common stock		(15,500)			(15,500)
Stock-based and deferred compensation		5,220	141	8,407	(3,328)
Net income		112,750					112,762	(12)
Other comprehensive income		(41,966)				(41,920)		(46)
Cash dividends paid:
Common stock		(20,857)					(20,857)
Other	[1]	(198)					(198)
Ending Balance at Dec. 31, 2018		$ 784,526	$ 26,309	$ 182,881	$ (97,389)	$ (141,483)	$ 813,448	$ 760

[1] Includes beginning retained earnings adjustment as a result of the Company’s first quarter 2018 adoption of ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory.