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
Impact of adoption of ASU 2016-09	$ 454		$ 0	$ 454
Adjusted equity balance	600,499	$ 37	322,246	427,518	$ (45,710)	$ (103,816)	$ 224
Beginning balance (in shares) at Dec. 31, 2017		36,790,751				(2,902,018)
Beginning balance at Dec. 31, 2017	600,045	$ 37	322,246	427,064	(45,710)	$ (103,816)	224
Stock issued against stock-based compensation plans (in shares)		778,222
Stock issued against stock-based compensation plans	431	$ 1	430
Stock-based compensation	5,074		5,074
Acquisition of treasury stock (in shares)						(223,993)
Acquisition of treasury stock	(13,504)					$ (13,504)
Non-controlling interest	7						7
Other comprehensive income	(13,960)				(13,960)
Net income	23,158			23,158
Ending balance (in shares) at Mar. 31, 2018		37,568,973				(3,126,011)
Ending balance at Mar. 31, 2018	$ 601,705	$ 38	327,750	450,676	(59,670)	$ (117,320)	231
Beginning balance (in shares) at Dec. 31, 2018	34,222,476	37,850,544				(3,628,068)
Beginning balance at Dec. 31, 2018	$ 618,319	$ 38	364,179	484,244	(83,467)	$ (146,925)	250
Stock issued against stock-based compensation plans (in shares)		405,492
Stock issued against stock-based compensation plans	22		22
Stock-based compensation	6,956		6,956
Acquisition of treasury stock (in shares)						(262,531)
Acquisition of treasury stock	(15,408)					$ (15,408)
Allocation of equity component related to issuance costs on convertible senior notes	(13)		(13)
Non-controlling interest	9						9
Other comprehensive income	6,255				6,255
Net income	$ 14,695			14,695
Ending balance (in shares) at Mar. 31, 2019	34,365,437	38,256,036				(3,890,599)
Ending balance at Mar. 31, 2019	$ 630,835	$ 38	$ 371,144	$ 498,939	$ (77,212)	$ (162,333)	$ 259