Condensed Consolidated Statements of Equity - USD ($) $ in Thousands	Common Shares in Treasury [Member]	Common Stock [Member]	Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) [Member]	Non-controlling Interests [Member]	Total
Beginning Balances at Dec. 31, 2016	$ (160,936)	$ 93,436	$ 306,566	$ 114,690	$ (106,643)	$ 7,919	$ 255,032
Beginning Balances, shares at Dec. 31, 2016	9,996,000
Net income				42,923		427	43,350
Other comprehensive income (loss)					20,973	116	21,089
Stock-based compensation transactions	$ 6,656		(2,761)				3,895
Stock-based compensation transactions, shares	(255,000)
Distributions to noncontrolling interests						(474)	(474)
Ending Balances at Jun. 30, 2017	$ (154,280)	93,436	303,805	157,613	(85,670)	7,988	322,892
Ending Balances, shares at Jun. 30, 2017	9,741,000
Beginning Balances at Dec. 31, 2017	$ (147,056)	93,436	302,158	171,744	(75,468)	11,866	356,680
Beginning Balances, shares at Dec. 31, 2017	9,386,000
Net income				53,059		400	53,459
Other comprehensive income (loss)					(24,354)	(179)	(24,533)
Purchase of treasury stock	$ (6,014)						$ (6,014)
Purchase of treasury stock, shares	287,000						287,257
Stock-based compensation transactions	$ 8,898		(6,705)				$ 2,193
Stock-based compensation transactions, shares	(376,000)
Change in ownership interest			789			(2,228)	(1,439)
Distributions to noncontrolling interests						(775)	(775)
Ending Balances at Jun. 30, 2018	$ (144,172)	$ 93,436	$ 296,242	228,944	$ (99,822)	$ 9,084	383,712
Ending Balances, shares at Jun. 30, 2018	9,297,000
Adjustment for accounting standards update 2016-16				$ 4,141			$ 4,141