Restatement (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020
Current assets
Cash and cash equivalents	$ 9,233				$ 7,926
Accounts receivable, net of allowance for doubtful accounts and discounts & allowances of $1,350 at December 31, 2020	9,930				8,002
Allowance for doubtful accounts and discounts	1,170				1,350
Inventories, net	8,285				6,930
Prepaid expenses and other current assets	1,254				1,163
Refundable income taxes	344				31
Total current assets	29,046				24,052
Property, plant and equipment, net	20,130				21,048
Operating lease right-of use asset	216				345
Intangible assets
Goodwill and indefinite-lived intangibles	15,404				14,004
Other intangible assets, net	4,278				0
Total intangible assets	19,682				14,004
Other Assets	1,800				1,800
Total assets	70,874				61,249
Current liabilities
Accounts payable	6,614				5,592
Accrued expenses	3,724				2,196
Accrued income taxes	725				653
Total current liabilities	12,063				8,441
Line of credit	2,777				2,768
Operating lease liabilities	85				165
Deferred income taxes, net	3,201				2,944
Other long-term liabilities	147				77
Total liabilities	21,743				14,395
Commitments and contingencies	0				0
Stockholders’ equity
Preferred stock, no par value; 2,500 shares authorized; none issued	$ 0				$ 0
Preferred stock, par value	$ 0				$ 0
Preferred stock, shares authorized	2,500				2,500
Preferred stock, shares issued	0				0
Common stock, no par value; 40,000 shares authorized; 17,274 shares issued; 15,604 shares outstanding at 2020	$ 6,509				$ 6,509
Common stock, par value	$ 0				$ 0
Common stock, shares authorized	40,000				40,000
Common stock, shares issued	17,274				17,274
Common stock, shares outstanding	15,435				15,604
Paid-in capital	$ 2,552				$ 2,600
Treasury stock, at cost	(13,436)				(12,450)
Retained earnings	53,506				50,195
Total stockholders’ equity	49,131				46,854
Total liabilities and stockholders’ equity	$ 70,874				61,249
Previously Reported [Member]
Current assets
Cash and cash equivalents		$ 10,018	$ 10,412	$ 8,618	7,926	$ 7,616	$ 4,619	$ 1,978
Accounts receivable, net of allowance for doubtful accounts and discounts & allowances of $1,350 at December 31, 2020		9,828	9,157	9,961	8,002	8,159	7,737	8,430
Allowance for doubtful accounts and discounts		1,290	1,190	1,100	1,350	1,410	1,300	1,467
Inventories, net		7,572	7,291	6,736	6,930	6,472	6,653	6,883
Prepaid expenses and other current assets		1,315	908	1,110	1,163	1,339	1,086	1,279
Refundable income taxes		415	354	46	31	189	615	1,027
Total current assets		29,148	28,122	26,471	24,052	23,775	20,710	19,597
Property, plant and equipment, net		20,546	20,671	20,744	21,048	21,082	21,394	21,910
Operating lease right-of use asset		255	226	317	345	380	431	707
Intangible assets
Goodwill and indefinite-lived intangibles		14,224	12,824	12,824	12,824	12,824	12,824	12,824
Other intangible assets, net		4,367	0	0	0	35	74	113
Total intangible assets		18,591	12,824	12,824	12,824	12,859	12,898	12,937
Other Assets		1,800	1,800	1,800	1,800	1,800	1,800	1,800
Total assets		70,340	63,643	62,156	60,069	59,896	57,233	56,951
Current liabilities
Accounts payable		7,867	5,285	5,289	5,592	6,036	5,108	6,113
Accrued expenses		3,872	3,587	2,587	2,196	2,890	3,066	2,632
Accrued income taxes		100	106	1,215	653	176	92	116
Total current liabilities		12,839	8,978	9,091	8,441	9,102	11,023	8,861
Line of credit		2,777	2,777	2,774	2,768	2,763	2,757	2,751
Operating lease liabilities		113	107	143	165	198	239	427
Deferred income taxes, net		1,764	1,764	1,764	1,764	1,292	1,292	1,292
Other long-term liabilities		62	12	160	77	35	42	50
Total liabilities		21,281	13,638	13,932	13,215	13,390	12,596	13,381
Commitments and contingencies					0	0
Stockholders’ equity
Preferred stock, no par value; 2,500 shares authorized; none issued		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Preferred stock, par value		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Preferred stock, shares authorized		2,500	2,500	2,500	2,500	2,500	2,500	2,500
Preferred stock, shares issued		0	0	0	0	0	0	0
Common stock, no par value; 40,000 shares authorized; 17,274 shares issued; 15,604 shares outstanding at 2020		$ 6,509	$ 6,509	$ 6,509	$ 6,509	$ 6,509	$ 6,509	$ 6,509
Common stock, par value		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Common stock, shares authorized		40,000	40,000	40,000	40,000	40,000	40,000	40,000
Common stock, shares issued		17,274	17,274	17,274	17,274	17,274	17,274	17,274
Common stock, shares outstanding		15,435	15,650	15,604	15,604	15,605	15,592	15,558
Paid-in capital		$ 2,387	$ 2,488	$ 2,664	$ 2,600	$ 2,532	$ 2,587	$ 2,748
Treasury stock, at cost		(13,436)	(12,111)	(12,450)	(12,450)	(12,450)	(12,548)	(12,796)
Retained earnings		53,599	53,119	51,501	50,195	49,915	48,089	47,109
Total stockholders’ equity		49,059	50,005	48,224	46,854	46,506	44,637	43,570
Total liabilities and stockholders’ equity		70,340	63,643	62,156	60,069	59,896	57,233	56,951
Revision of Prior Period, Adjustment [Member]
Current assets
Cash and cash equivalents		0	0	0	0	0	0	0
Accounts receivable, net of allowance for doubtful accounts and discounts & allowances of $1,350 at December 31, 2020		0	0	0	0	0	0	0
Allowance for doubtful accounts and discounts		1,290	1,190	1,100	1,350	1,410	1,300	1,467
Inventories, net		0	0	0	0	0	0	0
Prepaid expenses and other current assets		0	0	0	0	0	0	0
Refundable income taxes		0	0	0	0	0	0	0
Total current assets		0	0	0	0	0	0	0
Property, plant and equipment, net		0	0	0	0	0	0	0
Operating lease right-of use asset		0	0	0	0	0	0	0
Intangible assets
Goodwill and indefinite-lived intangibles		1,180	1,180	1,180	1,180	1,180	1,180	1,180
Other intangible assets, net		0	0	0	0	0	0	0
Total intangible assets		1,180	1,180	1,180	1,180	1,180	1,180	1,180
Other Assets		0	0	0	0	0	0	0
Total assets		1,180	1,180	1,180	1,180	1,180	1,180	1,180
Current liabilities
Accounts payable		0	0	0	0	0	0	0
Accrued expenses		0	0	0	0	0	0	0
Accrued income taxes		0	0	0	0	0	0	0
Total current liabilities		0	0	0	0	0	0	0
Line of credit		0	0	0	0	0	0	0
Operating lease liabilities		0	0	0	0	0	0	0
Deferred income taxes, net		1,180	1,180	1,180	1,180	1,180	1,180	1,180
Other long-term liabilities		0	0	0	0	0	0	0
Total liabilities		1,180	1,180	1,180	1,180	1,180	1,180	1,180
Commitments and contingencies					0	0
Stockholders’ equity
Preferred stock, no par value; 2,500 shares authorized; none issued		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Preferred stock, par value		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Preferred stock, shares authorized		2,500	2,500	2,500	2,500	2,500	2,500	2,500
Preferred stock, shares issued		0	0	0	0	0	0	0
Common stock, no par value; 40,000 shares authorized; 17,274 shares issued; 15,604 shares outstanding at 2020		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Common stock, par value		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Common stock, shares authorized		40,000	40,000	40,000	40,000	40,000	40,000	40,000
Common stock, shares issued		17,274	17,274	17,274	17,274	17,274	17,274	17,274
Common stock, shares outstanding		15,435	15,650	15,604	15,604	15,605	15,592	15,558
Paid-in capital		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Treasury stock, at cost		0	0	0	0	0	0	0
Retained earnings		0	0	0	0	0	0	0
Total stockholders’ equity		0	0	0	0	0	0	0
Total liabilities and stockholders’ equity		1,180	1,180	1,180	1,180	1,180	1,180	1,180
As Restated [Member]
Current assets
Cash and cash equivalents		10,018	10,412	8,618	7,926	7,616	4,619	1,978
Accounts receivable, net of allowance for doubtful accounts and discounts & allowances of $1,350 at December 31, 2020		9,828	9,157	9,961	8,002	8,159	7,737	8,430
Allowance for doubtful accounts and discounts		1,290	1,190	1,100	1,350	1,410	1,300	1,467
Inventories, net		7,572	7,291	6,736	6,930	6,472	6,653	6,883
Prepaid expenses and other current assets		1,315	908	1,110	1,163	1,339	1,086	1,279
Refundable income taxes		415	354	46	31	189	615	1,027
Total current assets		29,148	28,122	26,471	24,052	23,775	20,710	19,597
Property, plant and equipment, net		20,546	20,671	20,744	21,048	21,082	21,394	21,910
Operating lease right-of use asset		255	226	317	345	380	431	707
Intangible assets
Goodwill and indefinite-lived intangibles		15,404	14,004	14,004	14,004	14,004	14,004	14,004
Other intangible assets, net		4,367	0	0	0	35	74	113
Total intangible assets		19,771	14,004	14,004	14,004	14,039	14,078	14,117
Other Assets		1,800	1,800	1,800	1,800	1,800	1,800	1,800
Total assets		71,520	64,823	63,336	61,249	61,076	58,413	58,131
Current liabilities
Accounts payable		7,867	5,285	5,289	5,592	6,036	5,108	6,113
Accrued expenses		3,872	3,587	2,587	2,196	2,890	3,066	2,632
Accrued income taxes		100	106	1,215	653	176	92	116
Total current liabilities		12,839	8,978	9,091	8,441	9,102	11,023	8,861
Line of credit		2,777	2,777	2,774	2,768	2,763	2,757	2,751
Operating lease liabilities		113	107	143	165	198	239	427
Deferred income taxes, net		2,944	2,944	2,944	2,944	2,472	2,472	2,472
Other long-term liabilities		62	12	160	77	35	42	50
Total liabilities		22,461	14,818	15,112	14,395	14,570	13,776	14,561
Commitments and contingencies					0	0
Stockholders’ equity
Preferred stock, no par value; 2,500 shares authorized; none issued		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Preferred stock, par value		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Preferred stock, shares authorized		2,500	2,500	2,500	2,500	2,500	2,500	2,500
Preferred stock, shares issued		0	0	0	0	0	0	0
Common stock, no par value; 40,000 shares authorized; 17,274 shares issued; 15,604 shares outstanding at 2020		$ 6,509	$ 6,509	$ 6,509	$ 6,509	$ 6,509	$ 6,509	$ 6,509
Common stock, par value		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Common stock, shares authorized		40,000	40,000	40,000	40,000	40,000	40,000	40,000
Common stock, shares issued		17,274	17,274	17,274	17,274	17,274	17,274	17,274
Common stock, shares outstanding		15,435	15,650	15,604	15,604	15,605	15,592	15,558
Paid-in capital		$ 2,387	$ 2,488	$ 2,664	$ 2,600	$ 2,532	$ 2,587	$ 2,748
Treasury stock, at cost		(13,436)	(12,111)	(12,450)	(12,450)	(12,450)	(12,548)	(12,796)
Retained earnings		53,599	53,119	51,501	50,195	49,915	48,089	47,109
Total stockholders’ equity		49,059	50,005	48,224	46,854	46,506	44,637	43,570
Total liabilities and stockholders’ equity		$ 71,520	$ 64,823	$ 63,336	$ 61,249	$ 61,076	$ 58,413	$ 58,131