CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2018		30,555,715
Beginning balance at Dec. 31, 2018	$ 420,338	$ 306	$ 234,699	$ 187,819	$ (12)	$ (2,474)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	20,174			20,174
Comprehensive income
Foreign exchange translation adjustments	(1)					(1)
Cash-flow Hedges	(192)					(192)
Pension obligation adjustments	0
Other comprehensive income (loss), net of tax	(193)					(193)
Issuance of common stock (in shares)		22,497
Issuance of common stock	16		16
Purchase of treasury shares	(23,853)		(23,845)		(8)
Stock-based compensation	2,762		2,762
Ending balance (in shares) at Mar. 31, 2019		30,578,212
Ending balance at Mar. 31, 2019	419,244	$ 306	213,632	207,993	(20)	(2,667)
Beginning balance (in shares) at Dec. 31, 2018		30,555,715
Beginning balance at Dec. 31, 2018	420,338	$ 306	234,699	187,819	(12)	(2,474)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	35,520
Comprehensive income
Foreign exchange translation adjustments	3
Cash-flow Hedges	(621)
Ending balance (in shares) at Jun. 30, 2019		30,591,472
Ending balance at Jun. 30, 2019	420,563	$ 306	200,036	223,339	(26)	(3,092)
Beginning balance (in shares) at Mar. 31, 2019		30,578,212
Beginning balance at Mar. 31, 2019	419,244	$ 306	213,632	207,993	(20)	(2,667)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	15,346			15,346
Comprehensive income
Foreign exchange translation adjustments	4					4
Cash-flow Hedges	(429)					(429)
Pension obligation adjustments	0
Other comprehensive income (loss), net of tax	(425)					(425)
Issuance of common stock (in shares)		13,260
Issuance of common stock	0		0
Purchase of treasury shares	(16,414)		(16,408)		(6)
Stock-based compensation	2,812		2,812
Ending balance (in shares) at Jun. 30, 2019		30,591,472
Ending balance at Jun. 30, 2019	$ 420,563	$ 306	200,036	223,339	(26)	(3,092)
Beginning balance (in shares) at Dec. 31, 2019	27,914,777	31,423,898
Beginning balance at Dec. 31, 2019	$ 400,878	$ 314	180,884	229,166	(35)	(9,451)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	8,576			8,576
Comprehensive income
Foreign exchange translation adjustments	(57)					(57)
Cash-flow Hedges	(1,836)					(1,836)
Pension obligation adjustments	0
Other comprehensive income (loss), net of tax	(1,893)					(1,893)
Issuance of common stock (in shares)		154,495
Issuance of common stock	2	$ 2
Purchase of treasury shares	(925)		(924)		(1)
Stock-based compensation	1,198		1,198
Ending balance (in shares) at Mar. 31, 2020		31,578,393
Ending balance at Mar. 31, 2020	$ 407,836	$ 316	181,158	237,742	(36)	(11,344)
Beginning balance (in shares) at Dec. 31, 2019	27,914,777	31,423,898
Beginning balance at Dec. 31, 2019	$ 400,878	$ 314	180,884	229,166	(35)	(9,451)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	20,005
Comprehensive income
Foreign exchange translation adjustments	(57)
Cash-flow Hedges	$ (1,909)
Ending balance (in shares) at Jun. 30, 2020	28,030,271	31,622,910
Ending balance at Jun. 30, 2020	$ 420,787	$ 316	182,753	249,171	(36)	(11,417)
Beginning balance (in shares) at Mar. 31, 2020		31,578,393
Beginning balance at Mar. 31, 2020	407,836	$ 316	181,158	237,742	(36)	(11,344)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	11,429			11,429
Comprehensive income
Foreign exchange translation adjustments	0					0
Cash-flow Hedges	(73)					(73)
Pension obligation adjustments	0
Other comprehensive income (loss), net of tax	(73)					(73)
Issuance of common stock (in shares)		44,517
Issuance of common stock	0
Purchase of treasury shares	(107)		(107)
Stock-based compensation	$ 1,702		1,702
Ending balance (in shares) at Jun. 30, 2020	28,030,271	31,622,910
Ending balance at Jun. 30, 2020	$ 420,787	$ 316	$ 182,753	$ 249,171	$ (36)	$ (11,417)