Quarterly Financial Data (Unaudited) - Condensed Consolidated Balance Sheets (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jan. 01, 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, net	73,686	71,645	69,832	65,167		64,101	61,965	61,145	62,291
Operating lease right-of-use asset, net	34,960	23,333	22,097	19,793	$ 21,200		0	0	0
Goodwill	27,816	25,188	7,624	7,587		7,576	7,374	7,658	7,941
Intangible assets, net of accumulated amortization	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
Current operating lease liabilities	7,620	5,485	4,851	4,456			0	0	0
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
Revolving Credit Facility				0			0	0	7,500
Operating lease liabilities	29,414	19,192	18,567	16,538			0	0	0
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)	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
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
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, net		73,059	70,658	66,128		65,099	63,000	62,217	63,400
Operating lease right-of-use asset, net		23,333	22,097	19,793			0	0	0
Goodwill		25,188	7,624	7,587		7,576	7,374	7,658	7,941
Intangible assets, net of accumulated amortization		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
Current operating lease liabilities		5,485	4,851	4,456			0	0	0
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
Revolving Credit Facility				0					7,500
Operating lease liabilities		19,192	18,567	16,538			0	0	0
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)		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, net		(1,414)	(826)	(961)		(998)	(1,035)	(1,072)	(1,109)
Operating lease right-of-use asset, net		0	0	0			0	0	0
Goodwill		0	0	0		0	0	0	0
Intangible assets, net of accumulated amortization		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
Current operating lease liabilities		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
Revolving Credit Facility				0					0
Operating lease liabilities		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)		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)