Unaudited Condensed Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period Of Adoption, Adjustment [Member]	Common Stock	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss	Treasury Stock	Retained Earnings
Balance at Dec. 31, 2018			$ 48	$ 437,250	$ (2,588)	$ (233,676)	$ 152,650
Balance (in shares) at Dec. 31, 2018			31,771,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from the sales of stock through the Employee Stock Purchase Plan (in shares)			4,000
Proceeds from the sales of stock through the Employee Stock Purchase Plan				85
Stock compensation related to restricted stock vesting and retirement savings plan contributions (in shares)			414,000
Stock compensation related to restricted stock vesting and retirement savings plan contributions			$ 1	8,355
Purchases of treasury stock and buyback of shares for taxes (in shares)			(717,000)
Purchases of treasury stock and buyback of shares for taxes						(20,225)
Issuance of stock in conjunction with acquisition				1,456
Issuance of stock in conjunction with acquisition (in shares)			54,000
Foreign currency translation adjustment	$ 237				237
Net income	15,554						15,554
Balance at Jun. 30, 2019	359,147		$ 49	447,146	(2,351)	(253,901)	168,204
Balance (in shares) at Jun. 30, 2019			31,526,000
Balance at Dec. 31, 2018			$ 48	437,250	(2,588)	(233,676)	152,650
Balance (in shares) at Dec. 31, 2018			31,771,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity component of convertible notes, net of tax	15,547
Debt issuance costs of convertible notes, net of tax	523
Balance at Dec. 31, 2019	$ 381,015	$ (315)	$ 49	455,465	(2,650)	(261,624)	189,775
Balance (in shares) at Dec. 31, 2019	31,686,991		31,687,000
Balance at Mar. 31, 2019			$ 49	441,541	(2,417)	(249,036)	159,676
Balance (in shares) at Mar. 31, 2019			31,599,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from the sales of stock through the Employee Stock Purchase Plan (in shares)			2,000
Proceeds from the sales of stock through the Employee Stock Purchase Plan				41
Stock compensation related to restricted stock vesting and retirement savings plan contributions (in shares)			34,000
Stock compensation related to restricted stock vesting and retirement savings plan contributions			$ 0	4,108
Purchases of treasury stock and buyback of shares for taxes (in shares)			(163,000)
Purchases of treasury stock and buyback of shares for taxes						(4,865)
Issuance of stock in conjunction with acquisition				1,456
Issuance of stock in conjunction with acquisition (in shares)			54,000
Foreign currency translation adjustment	$ 66				66
Net income	8,528						8,528
Balance at Jun. 30, 2019	359,147		$ 49	447,146	(2,351)	(253,901)	168,204
Balance (in shares) at Jun. 30, 2019			31,526,000
Balance at Dec. 31, 2019	$ 381,015	(315)	$ 49	455,465	(2,650)	(261,624)	189,775
Balance (in shares) at Dec. 31, 2019	31,686,991		31,687,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from the sales of stock through the Employee Stock Purchase Plan (in shares)			4,000
Proceeds from the sales of stock through the Employee Stock Purchase Plan				116
Stock compensation related to restricted stock vesting and retirement savings plan contributions (in shares)			358,000
Stock compensation related to restricted stock vesting and retirement savings plan contributions			$ 1	9,405
Equity component of convertible notes, net of tax	$ 15,547
Debt issuance costs of convertible notes, net of tax	523
Purchases of treasury stock and buyback of shares for taxes (in shares)			(114,000)
Purchases of treasury stock and buyback of shares for taxes						(4,861)
Issuance of stock in conjunction with acquisition				10,161
Issuance of stock in conjunction with acquisition (in shares)			337,000
Foreign currency translation adjustment	(1,052)				(1,052)
Net income	15,583						15,583
Balance at Jun. 30, 2020	$ 410,053		$ 50	475,147	(3,702)	(266,485)	205,043
Balance (in shares) at Jun. 30, 2020	32,272,286		32,272,000
Balance at Mar. 31, 2020		$ 0	$ 50	465,123	(3,624)	(266,459)	198,434
Balance (in shares) at Mar. 31, 2020			32,061,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from the sales of stock through the Employee Stock Purchase Plan (in shares)			3,000
Proceeds from the sales of stock through the Employee Stock Purchase Plan				76
Stock compensation related to restricted stock vesting and retirement savings plan contributions (in shares)			38,000
Stock compensation related to restricted stock vesting and retirement savings plan contributions			$ 0	4,679
Purchases of treasury stock and buyback of shares for taxes (in shares)			0
Purchases of treasury stock and buyback of shares for taxes						(26)
Issuance of stock in conjunction with acquisition				5,269
Issuance of stock in conjunction with acquisition (in shares)			170,000
Foreign currency translation adjustment	$ (78)				(78)
Net income	6,609						6,609
Balance at Jun. 30, 2020	$ 410,053		$ 50	$ 475,147	$ (3,702)	$ (266,485)	$ 205,043
Balance (in shares) at Jun. 30, 2020	32,272,286		32,272,000