Quarterly Results (Unaudited) (As Corrected) (Previously Reported Quarterly Results) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 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	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement Related Disclosures [Abstract]
Net sales	$ 122,574	$ 113,500	$ 119,437	$ 113,822	$ 112,340	$ 112,937	$ 109,588	$ 99,082	$ 469,333	$ 433,947	$ 405,232
Cost of sales		86,090	89,233	88,392	84,494	80,107	81,927	83,886	349,908	330,414	281,581
Gross profit	36,381	27,410	30,204	25,430	27,846	32,830	27,661	15,196	119,425	103,533	123,651
Selling, general and administrative expenses		12,374	12,912	13,677	10,723	12,667	13,153	11,651	52,077	48,194	49,371
Loss (gain) on disposal of assets		6	6	284	(3)	2	(4)	(7)	337	(12)	45
Income from operations		15,030	17,286	11,469	17,126	20,161	14,512	3,552	67,011	55,351	74,235
Interest income, net		9	31	9	25	36	67	68	66	196	298
Other (expense) income, net		(7)	17	(26)	(58)	5	12	(6)	(46)	(47)	91
Income before taxes		15,032	17,334	11,452	17,093	20,202	14,591	3,614	67,031	55,500	74,624
Income tax provision		742	3,943	2,695	4,129	5,688	2,894	460	13,320	13,171	20,794
Net income	$ 17,273	$ 14,290	$ 13,391	$ 8,757	$ 12,964	$ 14,514	$ 11,697	$ 3,154	$ 53,711	$ 42,329	$ 53,830
Earnings per share:
Basic (usd per share)	$ 0.33	$ 0.27	$ 0.26	$ 0.17	$ 0.25	$ 0.28	$ 0.22	$ 0.06	$ 1.03	$ 0.81	$ 1.02
Diluted (usd per share)	$ 0.33	$ 0.26	0.26	$ 0.17	0.25	$ 0.27	0.22	$ 0.06	1.02	0.80	1.01
Cash dividends declared per common share (in dollars per share)			$ 0.16		$ 0.16		$ 0.16		$ 0.32	$ 0.32	$ 0.26
Weighted average shares outstanding:
Basic (in shares)		52,111,444	52,120,272	51,992,150	52,086,247	52,238,796	52,383,842	52,433,902	52,079,865	52,284,616	52,572,496
Diluted (in shares)		52,722,127	52,474,199	52,369,660	52,420,529	52,627,541	52,717,787	52,910,223	52,635,415	52,667,939	53,078,734
Balance Sheet Data (at end of period):
Current assets	$ 187,549	$ 170,284	$ 168,360	$ 146,511	$ 140,658	$ 144,476	$ 154,428	$ 154,450	$ 187,549	$ 140,658
Total assets	371,424	351,900	341,981	319,238	307,994	313,804	320,034	306,708	371,424	307,994
Current liabilities	56,028	53,103	58,102	43,082	47,491	53,071	70,962	56,581	56,028	47,491
Deferred tax liabilities	15,297	12,873	12,577	10,168	9,259	7,097	6,493	6,471	15,297	9,259
Other long-term liabilities	3,639	3,669	3,791	3,442	1,801	1,838	1,746	1,645	3,639	1,801
Total stockholders' equity	$ 290,140	282,255	267,511	262,546	249,443	251,798	240,833	242,011	$ 290,140	249,443	$ 238,925	$ 208,410
Previously Reported
Income Statement Related Disclosures [Abstract]
Net sales		113,500	119,437	113,822	112,340	112,937	109,588	99,082		433,947	405,232
Cost of sales		86,115	89,262	88,029	84,545	80,174	82,003	83,692		330,414	281,835
Gross profit		27,385	30,175	25,793	27,795	32,763	27,585	15,390		103,533	123,397
Selling, general and administrative expenses		12,994	13,481	11,001	11,260	13,190	13,086	10,219		47,755	49,249
Loss (gain) on disposal of assets		6	6	284	(3)	2	(4)	(7)		(12)	45
Income from operations		14,385	16,688	14,508	16,538	19,571	14,503	5,178		55,790	74,103
Interest income, net		9	31	9	25	36	67	68		196	298
Other (expense) income, net		(7)	17	(26)	(58)	5	12	(6)		(47)	91
Income before taxes		14,387	16,736	14,491	16,505	19,612	14,582	5,240		55,939	74,492
Income tax provision		560	3,775	3,589	3,969	5,527	2,891	980		13,367	19,994
Net income		$ 13,827	$ 12,961	$ 10,902	$ 12,536	$ 14,085	$ 11,691	$ 4,260		$ 42,572	$ 54,498
Earnings per share:
Basic (usd per share)		$ 0.27	$ 0.25	$ 0.21	$ 0.24	$ 0.27	$ 0.22	$ 0.08		$ 0.81	$ 1.04
Diluted (usd per share)		$ 0.26	0.25	$ 0.21	0.24	$ 0.27	0.22	$ 0.08		0.81	1.03
Cash dividends declared per common share (in dollars per share)			$ 0.16		$ 0.16		$ 0.16			$ 0.32	$ 0.26
Weighted average shares outstanding:
Basic (in shares)		52,111,444	52,120,272	51,992,150	52,086,247	52,238,796	52,383,842	52,433,902		52,284,616	52,572,496
Diluted (in shares)		52,722,127	52,474,199	52,369,660	52,420,529	52,627,541	52,717,787	52,910,223		52,667,939	53,078,734
Balance Sheet Data (at end of period):
Current assets		$ 170,536	$ 168,630	$ 146,798	$ 140,861	$ 144,696	$ 154,665	$ 154,687		$ 140,861
Total assets		352,152	342,251	319,525	308,197	314,024	320,271	306,945		308,197
Current liabilities		53,882	58,953	44,000	48,071	53,716	71,673	57,292		48,071
Deferred tax liabilities		15,034	14,938	12,713	10,826	8,841	8,415	8,397		10,826
Other long-term liabilities		3,669	3,791	3,442	1,801	1,838	1,746	1,645		1,801
Total stockholders' equity		279,567	264,569	259,370	247,499	249,629	238,437	239,611		247,499	$ 237,226	205,898
Corrections
Income Statement Related Disclosures [Abstract]
Net sales		0	0	0	0	0	0	0		0	0
Cost of sales		(25)	(29)	363	(51)	(67)	(76)	194		0	(254)
Gross profit		25	29	(363)	51	67	76	(194)		0	254
Selling, general and administrative expenses		(620)	(569)	2,676	(537)	(523)	67	1,432		439	122
Loss (gain) on disposal of assets		0	0	0	0	0	0	0		0	0
Income from operations		645	598	(3,039)	588	590	9	(1,626)		(439)	132
Interest income, net		0	0	0	0	0	0	0		0	0
Other (expense) income, net		0	0	0	0	0	0	0		0	0
Income before taxes		645	598	(3,039)	588	590	9	(1,626)		(439)	132
Income tax provision		182	168	(894)	160	161	3	(520)		(196)	800
Net income		$ 463	$ 430	$ (2,145)	$ 428	$ 429	$ 6	$ (1,106)		$ (243)	$ (668)
Earnings per share:
Basic (usd per share)		$ 0	$ 0.01	$ (0.04)	$ 0.01	$ 0.01	$ 0	$ (0.02)		$ 0	$ (0.02)
Diluted (usd per share)		$ 0	0.01	$ (0.04)	0.01	$ 0	0	$ (0.02)		(0.01)	(0.02)
Cash dividends declared per common share (in dollars per share)			$ 0		$ 0		$ 0			$ 0	$ 0
Weighted average shares outstanding:
Basic (in shares)		0	0	0	0	0	0	0		0	0
Diluted (in shares)		0	0	0	0	0	0	0		0	0
Balance Sheet Data (at end of period):
Current assets		$ (252)	$ (270)	$ (287)	$ (203)	$ (220)	$ (237)	$ (237)		$ (203)
Total assets		(252)	(270)	(287)	(203)	(220)	(237)	(237)		(203)
Current liabilities		(779)	(851)	(918)	(580)	(645)	(711)	(711)		(580)
Deferred tax liabilities		(2,161)	(2,361)	(2,545)	(1,567)	(1,744)	(1,922)	(1,926)		(1,567)
Other long-term liabilities		0	0	0	0	0	0	0		0
Total stockholders' equity		$ 2,688	$ 2,942	$ 3,176	$ 1,944	$ 2,169	$ 2,396	$ 2,400		$ 1,944	$ 1,699	$ 2,512