Unaudited Condensed Consolidated Statement of Stockholders' Equity - 9 months ended Sep. 30, 2018 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Treasury Stock	Retained Earnings
Balance at Dec. 31, 2017	$ 366,351	$ 47	$ 403,906	$ (1,822)	$ (163,871)	$ 128,091
Balance (in shares) at Dec. 31, 2017	33,249,665	33,250,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from the sales of stock through the Employee Stock Purchase Plan (in shares)		6,000
Proceeds from the sales of stock through the Employee Stock Purchase Plan	$ 124		124
Stock compensation related to restricted stock vesting and retirement savings plan contributions (in shares)		421,000
Stock compensation related to restricted stock vesting and retirement savings plan contributions	11,560	$ 1	11,559
Purchases of treasury stock and buyback of shares for taxes (in shares)		(1,943,000)
Purchases of treasury stock and buyback of shares for taxes	(54,717)				(54,717)
Issuance of stock in conjunction with acquisition including stock attributed to future compensation (in shares)		201,000
Issuance of stock in conjunction with acquisition including stock attributed to future compensation	4,201		4,201		0
Surrender of stock in conjunction with net working capital settlement (in shares)		(14,000)
Surrender of stock in conjunction with net working capital settlement	(303)				(303)
Equity component of convertible notes, net of tax	15,547		15,547
Debt issuance costs of convertible notes allocated to equity, net of tax	(511)		(511)
Purchase of hedges on convertible notes, net of tax	(15,376)		(15,376)
Proceeds from issuance of warrants on convertible notes	12,060		12,060
Net income	17,083					17,083
Foreign currency translation adjustment	(1,015)			(1,015)
Balance at Sep. 30, 2018	$ 355,004	$ 48	$ 431,510	$ (2,837)	$ (218,891)	$ 145,174
Balance (in shares) at Sep. 30, 2018	31,920,534	31,921,000