Pension Plans (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 pension cost (benefit)
Service cost	$ 155	$ 151	$ 306	$ 302
Interest cost	1,901	1,759	3,781	3,518
Expected return on plan assets	(3,570)	(3,201)	(7,095)	(6,400)
Amortization of actuarial loss	706	912	1,398	1,822
Administrative expenses	110	47	220	94
Net pension cost (benefit)	$ (698)	$ (332)	$ (1,390)	$ (664)