Pension and Retirement Plans - Changes of the benefit obligation, the plan assets and funded status of the plans (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets, Beginning Balance	$ 8,238
Fair Value of Plan Assets, Ending Balance	9,740	$ 8,238
Pension
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	13,961	13,459
Interest cost	278	386
Changes in actuarial assumptions	331	1,288
Foreign exchange impact	629	(772)
Benefits paid	(370)	(400)
Projected benefit obligation	14,829	13,961
Fair Value of Plan Assets, Beginning Balance	8,238	8,270
Actual gain on plan assets	929	194
Company contributions	547	655
Foreign exchange impact	396	(481)
Benefits paid	(370)	(400)
Fair Value of Plan Assets, Ending Balance	9,740	8,238
Funded status \ net amount recognized	(5,089)	(5,723)
Pension \| U.S.
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	514	585
Interest cost	15	24
Changes in actuarial assumptions	7	15
Benefits paid	(110)	(110)
Projected benefit obligation	426	514
Company contributions	110	110
Benefits paid	(110)	(110)
Funded status \ net amount recognized	(426)	(514)
Pension \| International
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	13,447	12,874
Interest cost	263	362
Changes in actuarial assumptions	324	1,273
Foreign exchange impact	629	(772)
Benefits paid	(260)	(290)
Projected benefit obligation	14,403	13,447
Fair Value of Plan Assets, Beginning Balance	8,238	8,270
Actual gain on plan assets	929	194
Company contributions	437	545
Foreign exchange impact	396	(481)
Benefits paid	(260)	(290)
Fair Value of Plan Assets, Ending Balance	9,740	8,238
Funded status \ net amount recognized	(4,663)	(5,209)
Post Retirement
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	1,516	1,318
Service cost	38	34
Interest cost	46	53
Changes in actuarial assumptions	103	111
Projected benefit obligation	1,703	1,516
Funded status \ net amount recognized	(1,703)	(1,516)
Post Retirement \| U.S.
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	1,516	1,318
Service cost	38	34
Interest cost	46	53
Changes in actuarial assumptions	103	111
Projected benefit obligation	1,703	1,516
Funded status \ net amount recognized	$ (1,703)	$ (1,516)

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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Amount of foreign currency translation gain (loss) which (increases) decreases benefit obligation of defined benefit plan.

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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of payment to participant under defined benefit plan which decreases plan assets. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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Amount of foreign currency translation gain (loss) which increases (decreases) plan assets of defined benefit plan.

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Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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