Consolidated Statements of Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss)/Income	Treasury Stock	Non - Controlling Interest
Beginning balance (in shares) at Dec. 31, 2018		37,850,544				(3,628,068)
Beginning balance at Dec. 31, 2018	$ 618,319	$ 38	$ 364,179	$ 484,244	$ (83,467)	$ (146,925)	$ 250
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued against stock-based compensation plans (in shares)		444,539
Stock issued against stock-based compensation plans	338		338
Stock-based compensation	$ 14,111		14,111
Acquisition of treasury stock (in shares)	(438,025)					(460,691)
Acquisition of treasury stock	$ (27,538)					$ (27,538)
Allocation of equity component related to issuance costs on convertible notes	(13)		(13)
Non-controlling interest	(232)		18				(250)
Other comprehensive income (loss)	9,109				9,109
Net income	27,259			27,259
Ending balance (in shares) at Jun. 30, 2019		38,295,083				(4,088,759)
Ending balance at Jun. 30, 2019	641,353	$ 38	378,633	511,503	(74,358)	$ (174,463)	0
Beginning balance (in shares) at Mar. 31, 2019		38,256,036				(3,890,599)
Beginning balance at Mar. 31, 2019	630,835	$ 38	371,144	498,939	(77,212)	$ (162,333)	259
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued against stock-based compensation plans (in shares)		39,047
Stock issued against stock-based compensation plans	316		316
Stock-based compensation	$ 7,155		7,155
Acquisition of treasury stock (in shares)	(198,160)					(198,160)
Acquisition of treasury stock	$ (12,130)					$ (12,130)
Non-controlling interest	(241)		18				(259)
Other comprehensive income (loss)	2,854				2,854
Net income	12,564			12,564
Ending balance (in shares) at Jun. 30, 2019		38,295,083				(4,088,759)
Ending balance at Jun. 30, 2019	$ 641,353	$ 38	378,633	511,503	(74,358)	$ (174,463)	$ 0
Beginning balance (in shares) at Dec. 31, 2019	34,185,241	38,480,654				(4,295,413)
Beginning balance at Dec. 31, 2019	$ 670,001	$ 39	391,240	551,903	(84,892)	$ (188,289)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued against stock-based compensation plans (in shares)		337,711
Stock issued against stock-based compensation plans	960		960
Stock-based compensation	$ 12,504		12,504
Acquisition of treasury stock (in shares)	(175,765)					(202,366)
Acquisition of treasury stock	$ (13,995)					$ (13,995)
Other comprehensive income (loss)	(19,382)				(19,382)
Net income	$ 30,840			30,840
Ending balance (in shares) at Jun. 30, 2020	34,320,586	38,818,365				(4,497,779)
Ending balance at Jun. 30, 2020	$ 680,928	$ 39	404,704	582,743	(104,274)	$ (202,284)
Beginning balance (in shares) at Mar. 31, 2020		38,813,775				(4,497,779)
Beginning balance at Mar. 31, 2020	655,904	$ 39	396,939	574,314	(113,104)	$ (202,284)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued against stock-based compensation plans (in shares)		4,590
Stock issued against stock-based compensation plans	39		39
Stock-based compensation	$ 7,726		7,726
Acquisition of treasury stock (in shares)	0
Acquisition of treasury stock	$ 0
Other comprehensive income (loss)	8,830				8,830
Net income	$ 8,429			8,429
Ending balance (in shares) at Jun. 30, 2020	34,320,586	38,818,365				(4,497,779)
Ending balance at Jun. 30, 2020	$ 680,928	$ 39	$ 404,704	$ 582,743	$ (104,274)	$ (202,284)