Error Correction (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended	36 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Consolidated Statements of Income
Net Sales	$ 134,772	$ 113,500	$ 397,851	$ 346,759
Cost of sales	93,924	86,090	275,925	263,715
Gross profit	40,848	27,410	121,926	83,044
Selling, general and administrative expenses	14,716	12,374	45,869	38,963
Loss (gain) on disposal of assets	1	6	(61)	296
Income from operations	26,131	15,030	76,118	43,785
Interest income, net		9		49
Other income (expense), net	15	(7)	20	(16)
Income before taxes	26,156	15,032	76,228	43,818
Income tax provision	5,696	742	16,111	7,380	$ 300	$ 900
Net income	$ 20,460	$ 14,290	$ 60,117	$ 36,438
Earnings per share:
Basic (usd per share)	$ 0.39	$ 0.27	$ 1.15	$ 0.70
Diluted (usd per share)	0.38	0.26	1.14	0.69
Cash dividends declared per common share (in dollars per share)	$ 0	$ 0	$ 0.19	$ 0.16
Weighted average shares outstanding:
Basic (in shares)	52,260,551	52,111,444	52,174,705	52,086,209
Diluted (in shares)	53,151,295	52,722,127	52,955,049	52,624,583
Balance Sheet
Current assets	$ 225,531	$ 170,284	$ 225,531	$ 170,284				$ 187,549
Total assets	439,913	351,900	439,913	351,900				371,424
Current liabilities	61,506	53,103	61,506	53,103				56,028
Deferred income taxes	22,973	12,873	22,973	12,873				15,297
Total stockholders' equity	344,892	282,255	344,892	282,255	249,443		$ 322,695	290,140	$ 267,511
Share-based compensation	2,852	2,068	8,546	9,854
Profit sharing bonus plan expense	3,000	1,684	8,691	4,948
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity	344,892	282,255	344,892	282,255	249,443		322,695	290,140	267,511
Net income	20,460	14,290	60,117	36,438
Stock options exercised and restricted stock awards granted	4,346	3,598	18,519	11,283
Share-based compensation	2,852	2,068	8,546	9,854
Stock repurchased and retired	(5,474)	(5,289)	(22,520)	(16,460)
Dividends	13	77	(9,910)	(8,303)
Operating Activities
Net income	20,460	14,290	60,117	36,438
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			18,971	17,627
Provision for credit losses on accounts receivable, net of adjustments			193	91
Provision for excess and obsolete inventories			1,776	1,003
Share-based compensation			8,546	9,854
Loss (gain) on disposition of assets	1	6	(61)	296
Foreign currency transaction (gain) loss			18	(17)
Interest income on note receivable			(19)	(19)
Deferred income taxes	2,615	296	7,676	3,614
Changes in assets and liabilities:
Accounts receivable			5,011	(2,096)
Income taxes			(3,142)	2,283
Inventories			(6,994)	(4,014)
Prepaid expenses and other			(598)	(513)
Accounts payable			3,654	782
Deferred revenue			1,128	263
Accrued liabilities and donations			688	4,991
Net cash provided by operating activities			96,995	70,583
Investing Activities
Capital expenditures			(48,955)	(30,831)
Proceeds from sale of property, plant and equipment			61	68
Investment in certificates of deposits			0	(6,000)
Maturities of certificates of deposits			0	6,000
Principal payments from note receivable			38	39
Net cash used in investing activities			(48,856)	(30,724)
Financing Activities
Stock options exercised			18,519	11,283
Repurchase of stock			(21,390)	(15,437)
Employee taxes paid by withholding shares			(1,130)	(1,023)
Cash dividends paid to stockholders			(9,910)	(8,303)
Net cash used in financing activities			(13,911)	(13,480)
Net increase in cash, cash equivalents and restricted cash			34,228	26,379
Cash, cash equivalents and restricted cash, beginning of period			44,373	1,994
Cash, cash equivalents and restricted cash, end of period	78,601	28,373	78,601	28,373	1,994
Common Stock
Balance Sheet
Total stockholders' equity	$ 209	$ 209	$ 209	$ 209	$ 208		$ 209	$ 208	$ 209
Consolidated Statements of Stockholders’ Equity
Shares, Outstanding	52,265,000	52,119,000	52,265,000	52,119,000	51,991,000		52,234,000	52,079,000	52,118,000
Total stockholders' equity	$ 209	$ 209	$ 209	$ 209	$ 208		$ 209	$ 208	$ 209
Stock options exercised and restricted stock awards granted (in shares)	126,000	110,000	616,000	494,000
Stock options exercised and restricted stock awards granted	$ 0		$ 2	$ 2
Stock repurchased and retired (in shares)	(95,000)	(109,000)	(430,000)	(366,000)
Stock repurchased and retired			$ (1)	$ (1)
Paid-in Capital
Balance Sheet
Total stockholders' equity	$ 8,175	$ 4,676	8,175	4,676	0		6,451	3,631	4,299
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity	8,175	4,676	8,175	4,676	0		6,451	3,631	4,299
Stock options exercised and restricted stock awards granted	4,346	3,598	18,517	11,281
Share-based compensation	2,852	2,068	8,546	9,854
Stock repurchased and retired	(5,474)	(5,289)	(22,519)	(16,459)
Retained Earnings
Consolidated Statements of Income
Net income	20,460	14,290	60,117	36,438
Balance Sheet
Total stockholders' equity	336,508	277,370	336,508	277,370	249,235		316,035	286,301	263,003
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity	336,508	277,370	336,508	277,370	249,235		$ 316,035	$ 286,301	263,003
Net income	20,460	14,290	60,117	36,438
Stock repurchased and retired	0
Dividends	13	77	(9,910)	(8,303)
Operating Activities
Net income	$ 20,460	14,290	$ 60,117	36,438
Previously Reported
Consolidated Statements of Income
Net Sales		113,500		346,759
Cost of sales		86,115		263,406
Gross profit		27,385		83,353
Selling, general and administrative expenses		12,994		37,476
Loss (gain) on disposal of assets		6		296
Income from operations		14,385		45,581
Interest income, net		9		49
Other income (expense), net		(7)		(16)
Income before taxes		14,387		45,614
Income tax provision		560		7,924
Net income		$ 13,827		$ 37,690
Earnings per share:
Basic (usd per share)		$ 0.27		$ 0.72
Diluted (usd per share)		0.26		0.72
Cash dividends declared per common share (in dollars per share)		$ 0		$ 0.16
Weighted average shares outstanding:
Basic (in shares)		52,111,444		52,086,209
Diluted (in shares)		52,722,127		52,624,583
Balance Sheet
Current assets		$ 170,536		$ 170,536
Total assets		352,152		352,152
Current liabilities		53,882		53,882
Deferred income taxes		15,034		15,034
Total stockholders' equity		279,567		279,567	247,499				264,569
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity		279,567		279,567	247,499				264,569
Net income		13,827		37,690
Stock options exercised and restricted stock awards granted		3,598		11,283
Share-based compensation		2,785		7,858
Stock repurchased and retired		(5,289)		(16,460)
Dividends		77		(8,303)
Operating Activities
Net income		13,827		37,690
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization				17,627
Provision for credit losses on accounts receivable, net of adjustments				91
Provision for excess and obsolete inventories				1,003
Share-based compensation				7,858
Loss (gain) on disposition of assets		6		296
Foreign currency transaction (gain) loss				(17)
Interest income on note receivable				(19)
Deferred income taxes				4,208
Changes in assets and liabilities:
Accounts receivable				(2,096)
Income taxes				(2,234)
Inventories				(4,014)
Prepaid expenses and other				(513)
Accounts payable				782
Deferred revenue				263
Accrued liabilities and donations				5,190
Net cash provided by operating activities				70,583
Investing Activities
Capital expenditures				(30,831)
Proceeds from sale of property, plant and equipment				68
Investment in certificates of deposits				(6,000)
Maturities of certificates of deposits				6,000
Principal payments from note receivable				39
Net cash used in investing activities				(30,724)
Financing Activities
Stock options exercised				11,283
Repurchase of stock				(15,437)
Employee taxes paid by withholding shares				(1,023)
Cash dividends paid to stockholders				(8,303)
Net cash used in financing activities				(13,480)
Net increase in cash, cash equivalents and restricted cash				26,379
Cash, cash equivalents and restricted cash, beginning of period				1,994
Cash, cash equivalents and restricted cash, end of period		28,373		28,373	1,994
Previously Reported | Common Stock
Balance Sheet
Total stockholders' equity		$ 209		$ 209	$ 208				$ 209
Consolidated Statements of Stockholders’ Equity
Shares, Outstanding		52,119,000		52,119,000	51,991,000				52,118,000
Total stockholders' equity		$ 209		$ 209	$ 208				$ 209
Stock options exercised and restricted stock awards granted (in shares)		110,000		494,000
Stock options exercised and restricted stock awards granted				$ 2
Stock repurchased and retired (in shares)		(109,000)		(366,000)
Stock repurchased and retired				$ (1)
Previously Reported | Paid-in Capital
Balance Sheet
Total stockholders' equity		$ 2,680		2,680	0				1,586
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity		2,680		2,680	0				1,586
Stock options exercised and restricted stock awards granted		3,598		11,281
Share-based compensation		2,785		7,858
Stock repurchased and retired		(5,289)		(16,459)
Previously Reported | Retained Earnings
Consolidated Statements of Income
Net income		13,827		37,690
Balance Sheet
Total stockholders' equity		276,678		276,678	247,291				262,774
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity		276,678		276,678	247,291				262,774
Net income		13,827		37,690
Dividends		77		(8,303)
Operating Activities
Net income		13,827		37,690
Corrections
Consolidated Statements of Income
Net Sales		0		0
Cost of sales		(25)		309
Gross profit		25		(309)
Selling, general and administrative expenses		(620)		1,487
Loss (gain) on disposal of assets		0		0
Income from operations		645		(1,796)
Interest income, net		0		0
Other income (expense), net		0		0
Income before taxes		645		(1,796)
Income tax provision		182		(544)
Net income		$ 463		$ (1,252)
Earnings per share:
Basic (usd per share)		$ 0		$ (0.02)
Diluted (usd per share)		0		(0.03)
Cash dividends declared per common share (in dollars per share)		$ 0		$ 0
Weighted average shares outstanding:
Basic (in shares)		0		0
Diluted (in shares)		0		0
Balance Sheet
Current assets		$ (252)		$ (252)
Total assets		(252)		(252)
Current liabilities		(779)		(779)
Deferred income taxes		(2,161)		(2,161)
Total stockholders' equity		2,688		2,688	1,944				2,942
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity		2,688		2,688	1,944				2,942
Net income		463		(1,252)
Stock options exercised and restricted stock awards granted		0		0
Share-based compensation		(717)		1,996
Stock repurchased and retired		0		0
Dividends		0		0
Operating Activities
Net income		463		(1,252)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization				0
Provision for credit losses on accounts receivable, net of adjustments				0
Provision for excess and obsolete inventories				0
Share-based compensation				1,996
Loss (gain) on disposition of assets		0		0
Foreign currency transaction (gain) loss				0
Interest income on note receivable				0
Deferred income taxes				(594)
Changes in assets and liabilities:
Accounts receivable				0
Income taxes				(49)
Inventories				0
Prepaid expenses and other				0
Accounts payable				0
Deferred revenue				0
Accrued liabilities and donations				(199)
Net cash provided by operating activities				0
Investing Activities
Capital expenditures				0
Proceeds from sale of property, plant and equipment				0
Investment in certificates of deposits				0
Maturities of certificates of deposits				0
Principal payments from note receivable				0
Net cash used in investing activities				0
Financing Activities
Stock options exercised				0
Repurchase of stock				0
Employee taxes paid by withholding shares				0
Cash dividends paid to stockholders				0
Net cash used in financing activities				0
Net increase in cash, cash equivalents and restricted cash				0
Cash, cash equivalents and restricted cash, beginning of period				0
Cash, cash equivalents and restricted cash, end of period		0		0	0
Corrections | Common Stock
Balance Sheet
Total stockholders' equity		$ 0		$ 0	$ 0				$ 0
Consolidated Statements of Stockholders’ Equity
Shares, Outstanding		0		0	0				0
Total stockholders' equity		$ 0		$ 0	$ 0				$ 0
Corrections | Paid-in Capital
Balance Sheet
Total stockholders' equity		1,996		1,996	0				2,713
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity		1,996		1,996	0				2,713
Share-based compensation		(717)		1,996
Corrections | Retained Earnings
Consolidated Statements of Income
Net income		463		(1,252)
Balance Sheet
Total stockholders' equity		692		692	1,944				229
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity		692		692	$ 1,944				$ 229
Net income		463		(1,252)
Operating Activities
Net income		463		(1,252)
Corrections | Cost of Sales
Balance Sheet
Share-based compensation		100		300
Corrections | Selling, General and Administrative Expenses
Balance Sheet
Share-based compensation		700		1,700
Profit sharing bonus plan expense		$ 100		$ 200