Pension and Retirement Plans - Components of net periodic benefit costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pension
Pension:
Interest cost	$ 70	$ 97
Expected return on plan assets	(74)	(77)
Amortization of:
Amortization of past service costs	1
Amortization of net gain	49	37
Net periodic benefit cost	46	57
Post Retirement
Pension:
Service cost	10	9
Interest cost	12	13
Amortization of:
Amortization of net gain	6	(5)
Net periodic benefit cost	28	17
U.S. | Pension
Pension:
Interest cost	4	6
Amortization of:
Amortization of net gain	1	(1)
Net periodic benefit cost	5	5
U.S. | Post Retirement
Pension:
Service cost	10	9
Interest cost	12	13
Amortization of:
Amortization of net gain	6	(5)
Net periodic benefit cost	28	17
U.K. | Pension
Pension:
Interest cost	66	91
Expected return on plan assets	(74)	(77)
Amortization of:
Amortization of past service costs	1
Amortization of net gain	48	38
Net periodic benefit cost	$ 41	$ 52