Restatement of Previously Issued Consolidated Financial Statements - Effect of The Error Correction On The Company’s Consolidated Balance Sheet (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash	$ 39,511	$ 38,703	$ 60,521	$ 54,348	$ 70,913	$ 57,525	$ 44,674	$ 37,908
Accounts receivable, net of allowances	115,099	153,190	157,193	158,327	133,935	150,507	150,576	141,821
Inventories	82,872	90,186	92,913	97,280	92,359	93,195	91,109	94,637
Other current assets	18,490	14,897	14,632	15,001	12,080	10,446	11,367	16,461
Total current assets	255,972	296,976	325,259	324,956	309,287	311,673	297,726	290,827
Property, Plant and Equipment:
Land and buildings	29,153				26,240
Machinery and equipment	186,511				173,771
Construction in progress	12,961				6,650
Less accumulated depreciation	(154,939)				(142,560)
Property, plant and equipment, net	73,686	71,645	69,832	65,167	64,101	61,965	61,145	62,291
Goodwill	27,816	25,188	7,624	7,587	7,576	7,374	7,658	7,941
Intangible assets, net of accumulated amortization of of $9,568	25,258	28,841	12,188	12,492	12,800	12,987	13,542	14,121
Deferred income taxes, net	14,654	14,117	13,387	14,243	16,341	12,499	14,303	18,447
Other assets	3,480	2,394	2,322	2,771	2,583	3,814	3,562	3,187
TOTAL ASSETS	435,826	462,494	452,709	447,009	412,688	410,312	397,936	396,814
Current Liabilities:
Accounts payable	63,058	88,835	93,320	96,305	86,645	91,582	88,473	85,602
Accrued liabilities and other	32,673	38,885	34,936	35,697	36,969	34,400	31,870	31,761
Current portion of long-term debt	3,256	3,335	3,238	3,229	9,102	3,217	3,208	3,199
Total current liabilities	106,607	136,540	136,345	139,687	132,716	129,199	123,551	120,562
Long-term debt	153,128	154,950	154,758	155,572	154,656	161,340	162,145	162,951
Pension and other post-retirement liabilities	10,666	13,417	11,812	12,489	12,065	14,534	14,429	15,367
Other long-term liabilities	7,323	7,607	2,342	2,658	3,655	4,582	6,622	6,862
Total liabilities	307,138	331,706	323,824	326,944	303,092	309,655	306,747	313,242
Stockholders’ Equity:
Preferred stock, $.01 par value (5,000,000 shares authorized; no shares issued and outstanding)	0	0	0	0	0	0	0	0
Common stock, $.01 par value (60,000,000 shares authorized; 30,512,843 shares issued and outstanding)	323	319	319	318	318	304	304	304
Treasury stock, at cost: 1,334,251 shares	(11,230)	(10,245)	(10,245)	(10,245)	(10,245)	(9,114)	(9,114)	(9,114)
Additional paid-in capital	245,852	245,207	244,486	243,768	243,007	242,167	241,387	240,543
Retained deficit	(60,307)	(52,773)	(59,953)	(66,099)	(76,013)	(84,110)	(95,387)	(108,058)		$ (115,233)
Accumulated other comprehensive loss	(45,950)	(51,720)	(45,722)	(47,677)	(47,471)	(48,590)	(46,001)	(40,103)
Total stockholders’ equity	128,688	130,788	128,885	120,065	109,596	100,657	91,189	83,572	$ 72,323	65,835
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	435,826	$ 462,494	$ 452,709	$ 447,009	412,688	410,312	397,936	396,814
Accounts receivable, allowances	4,634				5,139
Accumulated amortization on intangible assets	$ 11,440				$ 9,568
Preferred stock, par value (in dollars per shares)	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000	5,000,000	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0	0	0	0
Preferred stock, shares outstanding (in shares)	0	0	0	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	60,000,000	60,000,000	60,000,000	60,000,000	60,000,000
Common stock, shares issued (in shares)	30,801,255				30,512,843
Common stock, shares outstanding (in shares)	30,801,255				30,512,843
Treasury stock, shares (in shares)	1,464,392	1,334,251	1,334,251	1,334,251	1,334,251
As Previously Reported
Current Assets:
Cash		$ 38,703	$ 60,521	$ 54,348	$ 70,913	57,525	44,674	37,908
Accounts receivable, net of allowances		153,190	157,882	159,016	134,624	151,196	150,606	141,823
Inventories		90,186	92,913	97,280	92,359	93,195	91,109	94,637
Other current assets		24,496	22,370	21,257	16,828	14,137	13,981	18,385
Total current assets		306,575	333,686	331,901	314,724	316,053	300,370	292,753
Property, Plant and Equipment:
Land and buildings					26,240
Machinery and equipment					175,990
Construction in progress					6,650
Less accumulated depreciation					(143,781)
Property, plant and equipment, net		73,059	70,658	66,128	65,099	63,000	62,217	63,400
Goodwill		25,188	7,624	7,587	7,576	7,374	7,658	7,941
Intangible assets, net of accumulated amortization of of $9,568		28,841	12,188	12,492	12,800	12,987	13,542	14,121
Deferred income taxes, net		12,061	11,751	12,923	15,348	11,742	13,939	18,240
Other assets		2,394	2,322	2,771	2,583	3,814	3,562	3,187
TOTAL ASSETS		471,451	460,326	453,595	418,130	414,970	401,288	399,642
Current Liabilities:
Accounts payable		88,835	93,320	96,305	86,645	91,582	88,473	85,602
Accrued liabilities and other		38,885	34,936	35,697	36,969	34,400	31,870	31,761
Current portion of long-term debt		3,335	3,238	3,229	9,102	3,217	3,208	3,199
Total current liabilities		136,540	136,345	139,687	132,716	129,199	123,551	120,562
Long-term debt		154,950	154,758	155,572	154,656	161,340	162,145	162,951
Pension and other post-retirement liabilities		13,417	11,812	12,489	12,065	14,534	14,429	15,367
Other long-term liabilities		7,607	2,342	2,658	3,655	4,582	6,622	6,862
Total liabilities		331,706	323,824	326,944	303,092	309,655	306,747	313,242
Stockholders’ Equity:
Preferred stock, $.01 par value (5,000,000 shares authorized; no shares issued and outstanding)		0	0	0	0	0	0	0
Common stock, $.01 par value (60,000,000 shares authorized; 30,512,843 shares issued and outstanding)		319	319	318	318	304	304	304
Treasury stock, at cost: 1,334,251 shares		(10,245)	(10,245)	(10,245)	(10,245)	(9,114)	(9,114)	(9,114)
Additional paid-in capital		245,207	244,486	243,768	243,007	242,167	241,387	240,543
Retained deficit		(43,816)	(52,336)	(59,513)	(70,571)	(79,452)	(92,035)	(105,230)		(113,378)
Accumulated other comprehensive loss		(51,720)	(45,722)	(47,677)	(47,471)	(48,590)	(46,001)	(40,103)
Total stockholders’ equity		139,745	136,502	126,651	115,038	105,315	94,541	86,400	74,742	67,690
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY		471,451	460,326	453,595	418,130	414,970	401,288	399,642
Restatement Adjustments
Current Assets:
Cash		0	0	0	0	0	0	0
Accounts receivable, net of allowances		0	(689)	(689)	(689)	(689)	(30)	(2)
Inventories		0	0	0	0	0	0	0
Other current assets		(9,599)	(7,738)	(6,256)	(4,748)	(3,691)	(2,614)	(1,924)
Total current assets		(9,599)	(8,427)	(6,945)	(5,437)	(4,380)	(2,644)	(1,926)
Property, Plant and Equipment:
Land and buildings					0
Machinery and equipment					(2,219)
Construction in progress					0
Less accumulated depreciation					1,221
Property, plant and equipment, net		(1,414)	(826)	(961)	(998)	(1,035)	(1,072)	(1,109)
Goodwill		0	0	0	0	0	0	0
Intangible assets, net of accumulated amortization of of $9,568		0	0	0	0	0	0	0
Deferred income taxes, net		2,056	1,636	1,320	993	757	364	207
Other assets		0	0	0	0	0	0	0
TOTAL ASSETS		(8,957)	(7,617)	(6,586)	(5,442)	(4,658)	(3,352)	(2,828)
Current Liabilities:
Accounts payable		0	0	0	0	0	0	0
Accrued liabilities and other		0	0	0	0	0	0	0
Current portion of long-term debt		0	0	0	0	0	0	0
Total current liabilities		0	0	0	0	0	0	0
Long-term debt		0	0	0	0	0	0	0
Pension and other post-retirement liabilities		0	0	0	0	0	0	0
Other long-term liabilities		0	0	0	0	0	0	0
Total liabilities		0	0	0	0	0	0	0
Stockholders’ Equity:
Preferred stock, $.01 par value (5,000,000 shares authorized; no shares issued and outstanding)		0	0	0	0	0	0	0
Common stock, $.01 par value (60,000,000 shares authorized; 30,512,843 shares issued and outstanding)		0	0	0	0	0	0	0
Treasury stock, at cost: 1,334,251 shares		0	0	0	0	0	0	0
Additional paid-in capital		0	0	0	0	0	0	0
Retained deficit		(8,957)	(7,617)	(6,586)	(5,442)	(4,658)	(3,352)	(2,828)	(2,400)	(1,855)
Accumulated other comprehensive loss		0	0	0	0	0	0	0
Total stockholders’ equity		(8,957)	(7,617)	(6,586)	(5,442)	(4,658)	(3,352)	(2,828)	$ (2,419)	$ (1,855)
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY		$ (8,957)	$ (7,617)	$ (6,586)	$ (5,442)	$ (4,658)	$ (3,352)	$ (2,828)