Debt - Narrative (Details)				3 Months Ended	9 Months Ended	12 Months Ended
	Feb. 19, 2021 USD ($)	Feb. 18, 2021	Apr. 10, 2020 USD ($)	Dec. 31, 2020	Jun. 30, 2021 USD ($) lender	Sep. 30, 2021 USD ($) customer	Sep. 30, 2020 USD ($)	Dec. 17, 2018 USD ($)	Aug. 08, 2018 USD ($)
Line of Credit Facility [Line Items]
Number of customer invoices factored | customer						1
Revolving credit agreement
Line of Credit Facility [Line Items]
Percentage of stock pledged on credit agreement	66.67%
Notes Payable to Banks
Line of Credit Facility [Line Items]
Weighted average interest rate, revolving credit facility						2.70%
Debt face amount						$ 1,465,000
Long-term loan repayment schedule period						72 months
Notes Payable to Banks | Minimum
Line of Credit Facility [Line Items]
Debt instrument, term						6 months
Notes Payable to Banks | Maximum
Line of Credit Facility [Line Items]
Debt instrument, term						12 months
Notes Payable to Banks | Euro Interbank Offered Rate (Euribor)
Line of Credit Facility [Line Items]
Basis spread on LIBOR						3.20%
Foreign subsidiary borrowings
Line of Credit Facility [Line Items]
Receivables pledged as collateral						$ 485,000	$ 1,859,000
Long-term debt						$ 6,632,000	$ 5,759,000
Foreign subsidiary borrowings | Euro Interbank Offered Rate (Euribor) | Minimum
Line of Credit Facility [Line Items]
Euribor variable interest rates						1.00%
Foreign subsidiary borrowings | Euro Interbank Offered Rate (Euribor) | Maximum
Line of Credit Facility [Line Items]
Euribor variable interest rates						4.20%
2018 Credit Agreement | Revolving credit agreement | Revolving credit agreement
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity									$ 30,000
Weighted average interest rate, revolving credit facility							1.70%
Debt issuance costs incurred						$ 45,000
Debt instrument, unamortized discount premium						86,000
Revolving line of credit, accumulated amortization of debt issuance costs						$ 17,000	$ 205,000
2018 Credit Agreement | Revolving credit agreement | Revolving credit agreement | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on LIBOR							1.50%
Export Credit Facility | Revolving credit agreement | Revolving credit agreement
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity	$ 7,000							$ 5,000
Weighted average interest rate, revolving credit facility						1.30%	1.20%
Export Credit Facility | Revolving credit agreement | Revolving credit agreement | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on LIBOR				1.00%		1.25%
Paycheck Protection Program Loan | Unsecured Debt
Line of Credit Facility [Line Items]
Debt instrument, term			2 years
Debt face amount			$ 5,025,000
Interest rate, fixed percentage			0.98%
Deferral term			6 months
Paycheck Protection Program Loan | Unsecured Debt | JPMORGAN CHASE BANK N.A.
Line of Credit Facility [Line Items]
Repayments of debt							$ 261,000
Long-term debt						$ 4,764,000	4,764,000
Credit Agreement | Revolving credit agreement
Line of Credit Facility [Line Items]
Fixed charge coverage ratio						1.1
Percent availability under revolving commitment		12.50%		12.50%		10.00%
Debt instrument, covenant combined commitment percentage						10.00%
Debt instrument, covenant combined borrowing base, percentage						10.00%
Debt instrument, covenant combined borrowing base, amount						$ 2,000
Receivables pledged as collateral						25,370,000	26,964,000
Credit Agreement | Revolving credit agreement | Revolving credit agreement
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity	28,000					35,000	35,000
Accordion feature, increase limit	10,000
Remaining borrowing capacity						$ 14,570,000	$ 13,284,000
Weighted average interest rate, revolving credit facility						1.84%
Commitment fee percentage				0.25%		0.25%
Credit Agreement | Revolving credit agreement | Revolving credit agreement | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on LIBOR						1.75%
Fifth Amendment to Credit Agreement and First Amendment to Export Credit Agreement | Revolving credit agreement | Revolving credit agreement
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity	$ 35,000
First Loan
Line of Credit Facility [Line Items]
Debt instrument, term					7 years
Debt face amount					$ 717,000
Debt instrument, number of lenders | lender					2
Debt instrument, decrease, forgiveness					$ 287,000
Second Loan
Line of Credit Facility [Line Items]
Debt instrument, term					5 years
Debt face amount					$ 303,000