Pensions and Other Post-retirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Components of Net Periodic Benefit Cost
Interest cost	$ 1,014	$ 975	$ 2,028	$ 1,950
Expected return on plan assets	(1,386)	(1,299)	(2,772)	(2,598)
Recognized net actuarial loss	460	575	921	1,150
Net pension expense	$ 88	$ 251	$ 177	$ 502