Pension and Post-retirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Pension Plans
Pension Plan and Retirement Benefits
Service cost	$ 1,309	$ 1,385	$ 3,929	$ 4,153
Interest cost	2,567	2,530	7,700	7,761
Expected return	(3,561)	(3,508)	(10,708)	(10,807)
Amortizations	402	1,268	1,205	3,851
Net periodic benefit cost	717	1,675	2,126	4,958
Postretirement Health Care Benefits
Pension Plan and Retirement Benefits
Service cost	79	83	237	251
Interest cost	1,088	1,078	3,264	3,234
Amortizations	372	750	1,116	2,250
Net periodic benefit cost	1,539	$ 1,911	4,617	$ 5,735
Contribution to plan			2,389
Expected future employer contribution	1,250		1,250
U.S. pension plan | Defined Benefit Pension Plans
Pension Plan and Retirement Benefits
Contribution to plan			3,000
Expected future employer contribution	1,500		1,500
U.K. pension plan | Defined Benefit Pension Plans
Pension Plan and Retirement Benefits
Contribution to plan			571
Expected future employer contribution	$ 211		$ 211