Pension and Retirement Plans - Components of net periodic benefit costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Pension:
Pension:
Interest cost	$ 70	$ 66	$ 213	$ 190
Expected return on plan assets	(118)	(103)	(354)	(299)
Amortization of:
Amortization of past service costs	2	2	6	6
Amortization of net (gain) loss	24	48	74	139
Net periodic benefit cost	(22)	13	(61)	36
Post Retirement:
Pension:
Service cost	9	8	31	31
Interest cost	12	13	35	35
Amortization of:
Amortization of net (gain) loss	(10)	(39)	(14)	(14)
Net periodic benefit cost	11	(18)	52	52
U.S. | Pension:
Pension:
Interest cost	2	3	7	8
Expected return on plan assets	0	0	0	0
Amortization of:
Amortization of past service costs	0	0	0	0
Amortization of net (gain) loss	0	1	1	3
Net periodic benefit cost	2	4	8	11
U.S. | Post Retirement:
Pension:
Service cost	9	8	31	31
Interest cost	12	13	35	35
Amortization of:
Amortization of net (gain) loss	(10)	(39)	(14)	(14)
Net periodic benefit cost	11	(18)	52	52
U.K. | Pension:
Pension:
Interest cost	68	63	206	182
Expected return on plan assets	(118)	(103)	(354)	(299)
Amortization of:
Amortization of past service costs	2	2	6	6
Amortization of net (gain) loss	24	47	73	136
Net periodic benefit cost	(24)	9	(69)	25
U.K. | Post Retirement:
Pension:
Service cost	0	0	0	0
Interest cost	0	0	0	0
Amortization of:
Amortization of net (gain) loss	0	0	0	0
Net periodic benefit cost	$ 0	$ 0	$ 0	$ 0