Pension and Retirement Plans - Components of net periodic benefit costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan Disclosure [Line Items]
Increase (decrease) in minimum liability included in other comprehensive income (loss)	$ (4,096)	$ (1,972)
U.K..
Defined Benefit Plan Disclosure [Line Items]
Increase (decrease) in minimum liability included in other comprehensive income (loss)	(3,509)	(1,794)
U.S.
Defined Benefit Plan Disclosure [Line Items]
Increase (decrease) in minimum liability included in other comprehensive income (loss)	(587)	(178)
Pension:
Defined Benefit Plan Disclosure [Line Items]
Interest cost	279	254
Expected return on plan assets	(449)	(398)
Amortization of past service costs	7	7
Amortization of net gain (loss)	98	185
Net periodic benefit cost	(65)	48
Increase (decrease) in minimum liability included in other comprehensive income (loss)	(3,529)	(1,802)
Pension: | International
Defined Benefit Plan Disclosure [Line Items]
Interest cost	268	243
Pension: | U.K..
Defined Benefit Plan Disclosure [Line Items]
Interest cost	268	243
Expected return on plan assets	(449)	(398)
Amortization of past service costs	7	7
Amortization of net gain (loss)	97	181
Net periodic benefit cost	(77)	33
Increase (decrease) in minimum liability included in other comprehensive income (loss)	(3,509)	(1,794)
Pension: | U.S.
Defined Benefit Plan Disclosure [Line Items]
Interest cost	11	11
Amortization of net gain (loss)	1	4
Net periodic benefit cost	12	15
Increase (decrease) in minimum liability included in other comprehensive income (loss)	(20)	(8)
Post Retirement:
Defined Benefit Plan Disclosure [Line Items]
Service cost	44	45
Interest cost	46	42
Amortization of net gain (loss)	(7)	50
Net periodic benefit cost	83	137
Increase (decrease) in minimum liability included in other comprehensive income (loss)	(567)	(170)
Post Retirement: | U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost	44	45
Interest cost	46	42
Amortization of net gain (loss)	(7)	50
Net periodic benefit cost	83	137
Increase (decrease) in minimum liability included in other comprehensive income (loss)	$ (567)	$ (170)