Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated other comprehensive income (loss)
Balance	$ 329,692	$ 310,205	$ 333,220	$ 333,772
Other comprehensive income (loss)	(1,223)	(2,051)	(204)	3,398
Balance	330,140	306,714	330,140	306,714
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss)
Balance	(41,546)	(67,245)	(42,565)	(72,694)
Other comprehensive income (loss) before reclassifications	(1,803)	(3,999)	(1,943)	(1,166)
Amounts reclassified from accumulated other comprehensive income (loss), Tax benefit	(207)	(116)	(621)	(1,631)
Other comprehensive income (loss)	(1,223)	(2,051)	(204)	3,398
Balance	(42,769)	(69,296)	(42,769)	(69,296)
Accumulated Defined Benefit Plans Adjustment | Defined Benefit Pension Plans
Accumulated other comprehensive income (loss)
Balance	(20,860)	(41,342)	(21,473)	(43,012)
Amounts reclassified from accumulated other comprehensive income (loss), Tax benefit	(108)	(75)	(325)	(1,036)
Other comprehensive income (loss)	307	1,240	920	2,910
Balance	(20,553)	(40,102)	(20,553)	(40,102)
Accumulated Defined Benefit Plans Adjustment | Postretirement Health Care Benefits
Accumulated other comprehensive income (loss)
Balance	(10,655)	(20,745)	(11,201)	(21,691)
Amounts reclassified from accumulated other comprehensive income (loss), Tax benefit	(99)	(41)	(296)	(595)
Other comprehensive income (loss)	273	708	819	1,654
Balance	(10,382)	(20,037)	(10,382)	(20,037)
Amortization of Pension and Postretirement Plan items
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	51	93	154	280
Amortization of Pension and Postretirement Plan items | Defined Benefit Pension Plans
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	51	93	154	280
Actuarial losses
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	736	1,971	2,206	5,915
Actuarial losses | Defined Benefit Pension Plans
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	364	1,222	1,091	3,666
Actuarial losses | Postretirement Health Care Benefits
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	372	749	1,115	2,249
Accumulated Translation Adjustment
Accumulated other comprehensive income (loss)
Balance	(10,031)	(5,158)	(9,891)	(7,991)
Other comprehensive income (loss) before reclassifications	(1,803)	(3,999)	(1,943)	(1,166)
Other comprehensive income (loss)	(1,803)	(3,999)	(1,943)	(1,166)
Balance	$ (11,834)	$ (9,157)	$ (11,834)	$ (9,157)