Error Correction (Restated Consolidated Statements) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Consolidated Statements of Income
Net Sales	$ 125,596	$ 119,437	$ 263,079	$ 233,259
Cost of sales	87,465	89,233	182,001	177,625
Gross profit	38,131	30,204	81,078	55,634
Selling, general and administrative expenses	15,939	12,912	31,153	26,589
Loss (gain) on disposal of assets	0	6	(62)	290
Income from operations	22,192	17,286	49,987	28,755
Interest income, net		31		40
Other income (expense), net	32	17	5	(9)
Income before taxes	22,243	17,334	50,072	28,786
Income tax provision	4,439	3,943	10,415	6,638
Net income	$ 17,804	$ 13,391	$ 39,657	$ 22,148
Earnings per share:
Basic (usd per share)	$ 0.34	$ 0.26	$ 0.76	$ 0.43
Diluted (usd per share)	0.34	0.25	0.75	0.42
Cash dividends declared per common share (in dollars per share)	$ 0.19	$ 0.16	$ 0.19	$ 0.16
Weighted average shares outstanding:
Basic (in shares)	52,099,694	52,120,272	52,160,348	52,087,626
Diluted (in shares)	52,750,401	52,747,199	52,885,491	52,589,845
Balance Sheet
Current assets	$ 219,775	$ 168,360	$ 219,775	$ 168,360		$ 187,549
Total assets	429,807	341,981	429,807	341,981		371,424
Current liabilities	76,620	58,102	76,620	58,102		56,028
Deferred income taxes	20,358	12,577	20,358	12,577		15,297
Total stockholders' equity	322,695	267,511	322,695	267,511	$ 306,323	290,140	$ 262,546	$ 249,443
Share-based compensation	3,343	2,379	5,694	7,786
Profit sharing bonus plan expense	2,524	1,958	5,691	3,264
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity	322,695	267,511	322,695	267,511	306,323	290,140	262,546	249,443
Net income	17,804	13,391	39,657	22,148
Stock options exercised and restricted stock awards granted	9,676	3,675	14,173	7,685
Share-based compensation	3,343	2,379	5,694	7,786
Stock repurchased and retired	(4,528)	(6,100)	(17,046)	(11,171)
Dividends	(9,923)	(8,380)	(9,923)	(8,380)
Operating Activities
Net income	17,804	13,391	39,657	22,148
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			12,340	11,760
Provision for losses on accounts receivable, net of adjustments			76	128
Provision for excess and obsolete inventories			(193)	1,153
Share-based compensation			5,694	7,786
Loss (gain) on disposition of assets	0	6	(62)	290
Foreign currency transaction (gain) loss			30	(13)
Interest income on note receivable			(12)	(26)
Deferred income taxes	5,228	2,409	5,061	3,318
Changes in assets and liabilities:
Accounts receivable			10,929	(14,983)
Income taxes			(4,382)	2,925
Inventories			(11,617)	(585)
Prepaid expenses and other			(568)	(650)
Accounts payable			2,893	(2,592)
Deferred revenue			473	172
Accrued liabilities and donations			2,423	5,041
Net cash provided by operating activities			62,762	35,872
Investing Activities
Capital expenditures			(33,510)	(16,784)
Proceeds from sale of property, plant and equipment			61	59
Investment in certificates of deposits			0	(6,000)
Maturities of certificates of deposits			0	2,000
Principal payments from note receivable			25	28
Net cash used in investing activities			(33,424)	(20,697)
Financing Activities
Stock options exercised			14,173	7,685
Repurchase of stock			(15,937)	(10,191)
Employee taxes paid by withholding shares			(1,102)	(980)
Net cash used in financing activities			(2,866)	(3,486)
Net increase in cash, cash equivalents and restricted cash			26,472	11,689
Cash, cash equivalents and restricted cash, beginning of period			44,373	1,994
Cash, cash equivalents and restricted cash, end of period	70,845	13,683	70,845	13,683
Common Stock
Balance Sheet
Total stockholders' equity	$ 209	$ 209	$ 209	$ 209	$ 208	$ 208	$ 208	$ 208
Consolidated Statements of Stockholders’ Equity
Shares, Outstanding	52,234,000	52,118,000	52,234,000	52,118,000	52,044,000	52,079,000	52,099,000	51,991,000
Total stockholders' equity	$ 209	$ 209	$ 209	$ 209	$ 208	$ 208	$ 208	$ 208
Stock options exercised and restricted stock awards granted (in shares)	278,000	147,000	490,000	384,000
Stock options exercised and restricted stock awards granted	$ 1	$ 1	$ 2	$ 2
Stock repurchased and retired (in shares)	(88,000)	(128,000)	(335,000)	(257,000)
Stock repurchased and retired			$ (1)	$ (1)
Paid-in Capital
Balance Sheet
Total stockholders' equity	$ 6,451	$ 4,299	6,451	4,299	0	3,631	4,346	0
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity	6,451	4,299	6,451	4,299	0	3,631	4,346	0
Stock options exercised and restricted stock awards granted	9,675	3,674	14,171	7,683
Share-based compensation	3,343	2,379	5,694	7,786
Stock repurchased and retired	(6,567)	(6,100)	(17,045)	(11,170)
Retained Earnings
Consolidated Statements of Income
Net income	17,804	13,391	39,657	22,148
Balance Sheet
Total stockholders' equity	316,035	263,003	316,035	263,003	306,115	286,301	257,992	249,235
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity	316,035	263,003	316,035	263,003	$ 306,115	$ 286,301	257,992	249,235
Net income	17,804	13,391	39,657	22,148
Stock repurchased and retired	2,039
Dividends	(9,923)	(8,380)	(9,923)	(8,380)
Operating Activities
Net income	$ 17,804	13,391	$ 39,657	22,148
Previously Reported
Consolidated Statements of Income
Net Sales		119,437		233,259
Cost of sales		89,262		177,291
Gross profit		30,175		55,968
Selling, general and administrative expenses		13,481		24,482
Loss (gain) on disposal of assets		6		290
Income from operations		16,688		31,196
Interest income, net		31		40
Other income (expense), net		17		(9)
Income before taxes		16,736		31,227
Income tax provision		3,775		7,364
Net income		$ 12,961		$ 23,863
Earnings per share:
Basic (usd per share)		$ 0.25		$ 0.46
Diluted (usd per share)		0.25		0.45
Cash dividends declared per common share (in dollars per share)		$ 0.16		$ 0.16
Weighted average shares outstanding:
Basic (in shares)		52,120,272		52,087,626
Diluted (in shares)		52,747,199		52,589,845
Balance Sheet
Current assets		$ 168,630		$ 168,630
Total assets		342,251		342,251
Current liabilities		58,953		58,953
Deferred income taxes		14,938		14,938
Total stockholders' equity		264,569		264,569			259,370	247,499
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity		264,569		264,569			259,370	247,499
Net income		12,961		23,863
Stock options exercised and restricted stock awards granted		3,675		7,685
Share-based compensation		3,043		5,073
Stock repurchased and retired		(6,100)		(11,171)
Dividends		(8,380)		(8,380)
Operating Activities
Net income		12,961		23,863
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization				11,760
Provision for losses on accounts receivable, net of adjustments				128
Provision for excess and obsolete inventories				1,153
Share-based compensation				5,073
Loss (gain) on disposition of assets		6		290
Foreign currency transaction (gain) loss				(13)
Interest income on note receivable				(26)
Deferred income taxes				4,112
Changes in assets and liabilities:
Accounts receivable				(14,983)
Income taxes				(2,858)
Inventories				(585)
Prepaid expenses and other				(650)
Accounts payable				(2,592)
Deferred revenue				172
Accrued liabilities and donations				5,312
Net cash provided by operating activities				35,872
Investing Activities
Capital expenditures				(16,784)
Proceeds from sale of property, plant and equipment				59
Investment in certificates of deposits				(6,000)
Maturities of certificates of deposits				2,000
Principal payments from note receivable				28
Net cash used in investing activities				(20,697)
Financing Activities
Stock options exercised				7,685
Repurchase of stock				(10,191)
Employee taxes paid by withholding shares				(980)
Net cash used in financing activities				(3,486)
Net increase in cash, cash equivalents and restricted cash				11,689
Cash, cash equivalents and restricted cash, beginning of period				1,994
Cash, cash equivalents and restricted cash, end of period		13,683		13,683
Previously Reported | Common Stock
Balance Sheet
Total stockholders' equity		$ 209		$ 209			$ 208	$ 208
Consolidated Statements of Stockholders’ Equity
Shares, Outstanding		52,118,000		52,118,000			52,099,000	51,991,000
Total stockholders' equity		$ 209		$ 209			$ 208	$ 208
Stock options exercised and restricted stock awards granted (in shares)		147,000		384,000
Stock options exercised and restricted stock awards granted		$ 1		$ 2
Stock repurchased and retired (in shares)		(128,000)		(257,000)
Stock repurchased and retired		$ 0		$ (1)
Previously Reported | Paid-in Capital
Balance Sheet
Total stockholders' equity		1,586		1,586			969	0
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity		1,586		1,586			969	0
Stock options exercised and restricted stock awards granted		3,674		7,683
Share-based compensation		3,043		5,073
Stock repurchased and retired		(6,100)		(11,170)
Previously Reported | Retained Earnings
Consolidated Statements of Income
Net income		12,961		23,863
Balance Sheet
Total stockholders' equity		262,774		262,774			258,193	247,291
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity		262,774		262,774			258,193	247,291
Net income		12,961		23,863
Stock repurchased and retired		0		0
Dividends		(8,380)		(8,380)
Operating Activities
Net income		12,961		23,863
Corrections
Consolidated Statements of Income
Net Sales		0		0
Cost of sales		(29)		334
Gross profit		29		(334)
Selling, general and administrative expenses		(569)		2,107
Loss (gain) on disposal of assets		0		0
Income from operations		598		(2,441)
Interest income, net		0		0
Other income (expense), net		0		0
Income before taxes		598		(2,441)
Income tax provision		168		(726)
Net income		$ 430		$ (1,715)
Earnings per share:
Basic (usd per share)		$ 0.01		$ (0.03)
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		$ (270)		$ (270)
Total assets		(270)		(270)
Current liabilities		(851)		(851)
Deferred income taxes		(2,361)		(2,361)
Total stockholders' equity		2,942		2,942			3,176	1,944
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity		2,942		2,942			3,176	1,944
Net income		430		(1,715)
Stock options exercised and restricted stock awards granted		0		0
Share-based compensation		(664)		2,713
Stock repurchased and retired		0		0
Dividends		0		0
Operating Activities
Net income		430		(1,715)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization				0
Provision for losses on accounts receivable, net of adjustments				0
Provision for excess and obsolete inventories				0
Share-based compensation				2,713
Loss (gain) on disposition of assets		0		0
Foreign currency transaction (gain) loss				0
Interest income on note receivable				0
Deferred income taxes				(794)
Changes in assets and liabilities:
Accounts receivable				0
Income taxes				(67)
Inventories				0
Prepaid expenses and other				0
Accounts payable				0
Deferred revenue				0
Accrued liabilities and donations				(271)
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
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
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
Stock options exercised and restricted stock awards granted (in shares)		0		0
Stock options exercised and restricted stock awards granted		$ 0		$ 0
Stock repurchased and retired (in shares)		0		0
Stock repurchased and retired		$ 0		$ 0
Corrections | Paid-in Capital
Balance Sheet
Total stockholders' equity		2,713		2,713			3,377	0
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity		2,713		2,713			3,377	0
Stock options exercised and restricted stock awards granted		0		0
Share-based compensation		(664)		2,713
Stock repurchased and retired		0		0
Corrections | Retained Earnings
Consolidated Statements of Income
Net income		430		(1,715)
Balance Sheet
Total stockholders' equity		229		229			(201)	1,944
Consolidated Statements of Stockholders’ Equity
Total stockholders' equity		229		229			$ (201)	$ 1,944
Net income		430		(1,715)
Stock repurchased and retired		0		0
Dividends		0		0
Operating Activities
Net income		430		(1,715)
Corrections | Cost of Sales
Balance Sheet
Share-based compensation		100		300
Corrections | Selling, General and Administrative Expenses
Balance Sheet
Share-based compensation		600		2,400
Profit sharing bonus plan expense		$ 100		$ 300