Restatement of Previously Issued Consolidated Financial Statements - Effect of The Error Corrections On The Consolidated Statements of Cash Flow (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income	$ (7,534)	$ 7,180	$ 6,146	$ 9,986	$ 8,097	$ 11,277	$ 12,671	$ 9,444	$ 16,132	$ 22,115	$ 23,312	$ 33,392	$ 15,778	$ 41,489	$ (2,269)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization				3,681				3,776	6,984	7,674	10,865	11,676	15,514	15,270	15,196
Provision for doubtful accounts				2,350				2,637	3,396	3,829	5,000	6,448	6,861	7,607	5,622
Noncash amortization of debt financing costs				342				350	685	701	1,030	1,054	1,393	1,404	1,251
Shared-based compensation expense				761				673	1,479	1,517	2,200	2,297	2,843	3,137	2,503
(Gain) loss on sale of assets															(586)
Deferred income taxes				2,298				2,181	2,263	6,396	1,840	8,369	1,562	5,031	7,709
Noncash (gain) loss on derivative contracts				737				(2,489)	1,823	(2,161)	2,092	(2,842)	1,972	(1,468)	(726)
Change in other operating items:
Accounts receivable				(26,356)				(34,884)	(26,552)	(47,306)	(25,454)	(50,389)	11,954	(34,987)	(13,792)
Inventories				(4,739)				5,261	(462)	7,010	1,191	4,507	9,495	4,836	(25,104)
Prepaid expenses				(2,272)				(1,496)	(2,501)	(2,507)	(2,607)	(2,126)	(1,793)	(2,292)	179
Accounts payable				9,548				(2,105)	6,563	2,845	3,272	6,653	(24,261)	1,451	23,250
Accrued liabilities													(3,525)	2,631	(12,284)
Other operating activities, net															1,308
Other operating activities, net				(2,307)				(3,363)	(1,061)	788	5,767	1,000	(1,047)	(3,117)	722
Net cash provided by operating activities				(5,971)				(20,015)	8,749	901	28,508	20,039	36,746	40,992	2,257
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant and equipment				(5,580)				(1,716)	(12,800)	(5,158)	(18,743)	(9,823)	(24,002)	(14,150)	(13,458)
Proceeds from disposal/sale of property, plant and equipment				20				0	20	0	20	18	23	49	2,682
Net cash used in investing activities				(5,560)				(1,716)	(12,780)	(5,158)	(52,723)	(9,805)	(57,979)	(14,101)	(10,776)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings of Revolving Credit Facility				0				36,500	0	80,500	8,500	80,500	35,700	80,500	0
Repayment of Revolving Credit Facility				0				(29,000)	0	(80,500)	(8,500)	(80,500)	(35,700)	(80,500)	0
Borrowings of Term Loan Facility													0	0	175,000
Repayment of Term Loan Facility				(5,244)				(1,094)	(6,338)	(2,188)	(6,338)	(3,281)	(8,525)	(4,375)	(2,188)
Surrender of common stock by employees													(985)	(1,131)	(1,361)
Redemption of Notes													0	0	(235,000)
Prepayment charge for redemption of Notes													0	0	(1,543)
Payment of Term Loan Facility discount													0	0	(3,500)
Payment of debt issuance costs													(160)	0	(4,256)
Other financing activities, net				(105)					(222)		(381)		(443)	(329)	0
Net cash used in financing activities				(5,349)				6,406	(6,560)	(2,188)	(6,719)	(3,281)	(10,113)	(5,835)	(72,848)
EFFECT OF CURRENCY EXCHANGE RATE CHANGES ON CASH				315				989	199	(1,125)	(1,276)	(1,672)	(56)	(2,387)	3,451
NET INCREASE (DECREASE) IN CASH				(16,565)				(14,336)	(10,392)	(7,570)	(32,210)	5,281	(31,402)	18,669	(77,916)
CASH:
Beginning of period	38,703	60,521	54,348	70,913	57,525	44,674	37,908	52,244	70,913	52,244	70,913	52,244	70,913	52,244	130,160
End of period	39,511	38,703	60,521	54,348	70,913	57,525	44,674	37,908	60,521	44,674	38,703	57,525	39,511	70,913	52,244
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid for interest				3,373				3,408	6,787	6,937	10,212	10,421	13,873	14,046	18,572
Cash paid for income taxes, net				2,593				808	4,180	1,693	5,530	2,081	8,774	3,143	3,276
Unpaid purchases of property and equipment included in accounts payable				233				49	526	416	155	132	624	509	109
As Previously Reported
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income		8,520	7,177	11,130	8,881	12,583	13,195	9,853	18,307	23,048	26,827	35,631		44,512	(1,705)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization				3,718				3,813	7,058	7,748	10,976	11,787		15,418	15,344
Provision for doubtful accounts				2,350				2,637	3,396	3,829	5,000	6,448		7,607	5,622
Noncash amortization of debt financing costs				342				350	685	701	1,030	1,054		1,404	1,251
Shared-based compensation expense				761				673	1,479	1,517	2,200	2,297		3,137	2,503
(Gain) loss on sale of assets															(586)
Deferred income taxes				2,625				2,304	2,906	6,676	2,903	9,042		5,940	7,992
Noncash (gain) loss on derivative contracts				737				(2,489)	1,823	(2,161)	2,092	(2,842)		(1,468)	(726)
Change in other operating items:
Accounts receivable				(26,356)				(34,884)	(26,552)	(47,334)	(24,765)	(51,076)		(35,674)	(13,794)
Inventories				(4,739)				5,261	(462)	7,010	1,191	4,507		4,836	(25,104)
Prepaid expenses				(3,780)				(2,065)	(5,491)	(3,766)	(7,458)	(4,462)		(5,685)	(814)
Accounts payable				9,548				(2,105)	6,563	2,845	3,272	6,653		1,451	23,250
Accrued liabilities														2,631	(12,284)
Other operating activities, net															1,308
Other operating activities, net				(2,307)				(3,363)	(1,061)	788	5,767	1,000		(3,117)
Net cash provided by operating activities				(5,971)				(20,015)	8,651	901	29,035	20,039		40,992	2,257
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant and equipment				(5,580)				(1,716)	(12,702)	(5,158)	(19,270)	(9,823)		(14,150)	(13,458)
Proceeds from disposal/sale of property, plant and equipment				20					20		20	18		49	2,682
Net cash used in investing activities				(5,560)				(1,716)	(12,682)	(5,158)	(53,250)	(9,805)		(14,101)	(10,776)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings of Revolving Credit Facility								36,500		80,500	8,500	80,500		80,500
Repayment of Revolving Credit Facility								(29,000)		(80,500)	(8,500)	(80,500)		(80,500)
Borrowings of Term Loan Facility															175,000
Repayment of Term Loan Facility				(5,244)				(1,094)	(6,338)	(2,188)	(6,338)	(3,281)		(4,375)	(2,188)
Surrender of common stock by employees														(1,131)	(1,361)
Redemption of Notes															(235,000)
Prepayment charge for redemption of Notes															(1,543)
Payment of Term Loan Facility discount															(3,500)
Payment of debt issuance costs															(4,256)
Other financing activities, net				(105)					(222)		(381)			(329)
Net cash used in financing activities				(5,349)				6,406	(6,560)	(2,188)	(6,719)	(3,281)		(5,835)	(72,848)
EFFECT OF CURRENCY EXCHANGE RATE CHANGES ON CASH				315				989	199	(1,125)	(1,276)	(1,672)		(2,387)	3,451
NET INCREASE (DECREASE) IN CASH				(16,565)				(14,336)	(10,392)	(7,570)	(32,210)	5,281		18,669	(77,916)
CASH:
Beginning of period	38,703	60,521	54,348	70,913	57,525	44,674	37,908	52,244	70,913	52,244	70,913	52,244	70,913	52,244	130,160
End of period		38,703	60,521	54,348	70,913	57,525	44,674	37,908	60,521	44,674	38,703	57,525		70,913	52,244
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid for interest				3,373				3,408	6,787	6,937	10,212	10,421		14,046	18,572
Cash paid for income taxes, net				2,593				808	4,180	1,693	5,530	2,081		3,143	3,276
Unpaid purchases of property and equipment included in accounts payable				233				49	526	416	155	132		509	109
Restatement Adjustments
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income		(1,340)	(1,031)	(1,144)	(784)	(1,306)	(524)	(409)	(2,175)	(933)	(3,515)	(2,239)		(3,023)	(564)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization				(37)				(37)	(74)	(74)	(111)	(111)		(148)	(148)
Provision for doubtful accounts				0				0	0	0	0	0		0	0
Noncash amortization of debt financing costs				0				0	0	0	0	0		0	0
Shared-based compensation expense				0				0	0	0	0	0		0	0
(Gain) loss on sale of assets															0
Deferred income taxes				(327)				(123)	(643)	(280)	(1,063)	(673)		(909)	(283)
Noncash (gain) loss on derivative contracts				0				0	0	0	0	0		0	0
Change in other operating items:
Accounts receivable				0				0	0	28	(689)	687		687	2
Inventories				0				0	0	0	0	0		0	0
Prepaid expenses				1,508				569	2,990	1,259	4,851	2,336		3,393	993
Accounts payable				0				0	0	0	0	0		0	0
Accrued liabilities														0	0
Other operating activities, net															0
Other operating activities, net				0				0	0	0	0	0		0
Net cash provided by operating activities				0				0	98	0	(527)	0		0	0
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant and equipment				0				0	(98)	0	527	0		0	0
Proceeds from disposal/sale of property, plant and equipment				0					0		0	0		0	0
Net cash used in investing activities				0				0	(98)	0	527	0		0	0
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings of Revolving Credit Facility								0		0	0	0		0
Repayment of Revolving Credit Facility								0		0	0	0		0
Borrowings of Term Loan Facility															0
Repayment of Term Loan Facility				0				0	0	0	0	0		0	0
Surrender of common stock by employees														0	0
Redemption of Notes															0
Prepayment charge for redemption of Notes															0
Payment of Term Loan Facility discount															0
Payment of debt issuance costs															0
Other financing activities, net				0					0		0			0
Net cash used in financing activities				0				0	0	0	0	0		0	0
EFFECT OF CURRENCY EXCHANGE RATE CHANGES ON CASH				0				0	0	0	0	0		0	0
NET INCREASE (DECREASE) IN CASH				0				0	0	0	0	0		0	0
CASH:
Beginning of period	$ 0	0	0	0	0	0	0	0	0	0	0	0	$ 0	0	0
End of period		$ 0	$ 0	0	$ 0	$ 0	$ 0	0	0	0	0	0		0	0
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid for interest				0				0	0	0	0	0		0	0
Cash paid for income taxes, net				0				0	0	0	0	0		0	0
Unpaid purchases of property and equipment included in accounts payable				$ 0				$ 0	$ 0	$ 0	$ 0	$ 0		$ 0	$ 0