Pension and Retirement Plans - Components of net periodic benefit costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Pension
Pension:
Interest cost	$ 61	$ 70
Expected return on plan assets	(97)	(74)
Amortization of:
Amortization of past service costs	2	1
Amortization of net gain (loss)	45	49
Net periodic benefit cost	11	46
Post Retirement
Pension:
Service cost	11	10
Interest cost	11	12
Amortization of:
Amortization of net gain (loss)	13	6
Net periodic benefit cost	35	28
U.S. | Pension
Pension:
Interest cost	3	4
Amortization of:
Amortization of net gain (loss)	1	1
Net periodic benefit cost	4	5
U.S. | Post Retirement
Pension:
Service cost	11	10
Interest cost	11	12
Amortization of:
Amortization of net gain (loss)	13	6
Net periodic benefit cost	35	28
U.K. | Pension
Pension:
Interest cost	58	66
Expected return on plan assets	(97)	(74)
Amortization of:
Amortization of past service costs	2	1
Amortization of net gain (loss)	44	48
Net periodic benefit cost	$ 7	$ 41