Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Capital in Excess of Par Value	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Income
Balance at beginning of year (in shares) at Dec. 31, 2019		9,043,771
Balance at beginning of year at Dec. 31, 2019	$ 108,001	$ 9,190	$ 18,077	$ 86,496	$ (5,761)	$ (1)
Net income	12,533			12,533
Adjustment for foreign currency translation	(2,494)					(2,494)
Stock-based compensation	451		451
Shares repurchased held in treasury (in shares)		(47,504)
Shares repurchased held in treasury	(1,756)				(1,756)
Balance at end of period (in shares) at Mar. 31, 2020		8,996,267
Balance at end of period at Mar. 31, 2020	116,735	$ 9,190	18,528	99,029	(7,517)	(2,495)
Balance at beginning of year (in shares) at Dec. 31, 2019		9,043,771
Balance at beginning of year at Dec. 31, 2019	108,001	$ 9,190	18,077	86,496	(5,761)	(1)
Net income	14,890
Adjustment for foreign currency translation	(918)
Balance at end of period (in shares) at Sep. 30, 2020		9,025,617
Balance at end of period at Sep. 30, 2020	121,254	$ 9,232	19,508	101,386	(7,953)	(919)
Balance at beginning of year (in shares) at Mar. 31, 2020		8,996,267
Balance at beginning of year at Mar. 31, 2020	116,735	$ 9,190	18,528	99,029	(7,517)	(2,495)
Net income	619			619
Adjustment for foreign currency translation	1,178					1,178
Stock-based compensation	498		498
Shares issued (in shares)		11,144
Shares issued	14	$ 11	3
Balance at end of period (in shares) at Jun. 30, 2020		9,007,411
Balance at end of period at Jun. 30, 2020	119,044	$ 9,201	19,029	99,648	(7,517)	(1,317)
Net income	1,738			1,738
Adjustment for foreign currency translation	398						$ 398
Stock-based compensation	510		510
Shares issued (in shares)		30,283
Shares issued	$ 0	$ 31	(31)
Shares repurchased held in treasury (in shares)	(12,077)
Shares repurchased held in treasury	$ (436)
Balance at end of period (in shares) at Sep. 30, 2020		9,025,617
Balance at end of period at Sep. 30, 2020	$ 121,254	$ 9,232	19,508	101,386	(7,953)	(919)
Balance at beginning of year (in shares) at Dec. 31, 2020	9,287,625	9,061,039
Balance at beginning of year at Dec. 31, 2020	$ 122,422	$ 9,288	19,841	101,609	(9,015)	699
Net income	3,596			3,596
Adjustment for foreign currency translation	631					631
Stock-based compensation	422		422
Shares issued (in shares)		5,776
Shares issued	0	$ 5	(5)
Shares repurchased held in treasury (in shares)		(268)
Shares repurchased held in treasury	(13)				(13)
Balance at end of period (in shares) at Mar. 31, 2021		9,066,547
Balance at end of period at Mar. 31, 2021	$ 127,058	$ 9,293	20,258	105,205	(9,028)	1,330
Balance at beginning of year (in shares) at Dec. 31, 2020	9,287,625	9,061,039
Balance at beginning of year at Dec. 31, 2020	$ 122,422	$ 9,288	19,841	101,609	(9,015)	699
Net income	10,187
Adjustment for foreign currency translation	$ 57
Balance at end of period (in shares) at Sep. 30, 2021	9,305,566	9,078,347
Balance at end of period at Sep. 30, 2021	$ 134,356	$ 9,306	21,546	111,796	(9,048)	756
Balance at beginning of year (in shares) at Mar. 31, 2021		9,066,547
Balance at beginning of year at Mar. 31, 2021	127,058	$ 9,293	20,258	105,205	(9,028)	1,330
Net income	2,935			2,935
Adjustment for foreign currency translation	354						354
Stock-based compensation	$ 551		551
Shares issued (in shares)	10,965
Shares issued	$ 0	$ 11	(11)
Balance at end of period (in shares) at Jun. 30, 2021		9,077,512
Balance at end of period at Jun. 30, 2021	130,898	$ 9,304	20,798	108,140	(9,028)	1,684
Net income	3,656			3,656
Adjustment for foreign currency translation	(928)						$ (928)
Stock-based compensation	$ 750		750
Shares issued (in shares)	1,200
Shares issued	$ 0	$ 2	(2)
Shares repurchased held in treasury (in shares)		(365)
Shares repurchased held in treasury	$ (20)				(20)
Balance at end of period (in shares) at Sep. 30, 2021	9,305,566	9,078,347
Balance at end of period at Sep. 30, 2021	$ 134,356	$ 9,306	$ 21,546	$ 111,796	$ (9,048)	$ 756