Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated other comprehensive income (loss)
Balance			$ 341,989
Net current-period other comprehensive income (loss)	$ (1,769)	$ 4,636	17	$ 1,898
Balance	336,928		336,928
AOCI Attributable to Parent
Accumulated other comprehensive income (loss)
Balance	(86,167)	(64,566)	(87,953)	(61,828)
Other comprehensive income (loss) before classifications	(3,745)	3,381	(5,911)	(1,864)
Amounts reclassified from accumulated other comprehensive income (loss), Tax benefit	1,151	737	3,450	2,214
Net current-period other comprehensive income (loss)	(1,769)	4,636	17	1,898
Balance	(87,936)	(59,930)	(87,936)	(59,930)
Defined Benefit Plans | Defined Benefit Pension Plans
Accumulated other comprehensive income (loss)
Balance	(59,926)	(41,058)	(62,985)	(42,800)
Amounts reclassified from accumulated other comprehensive income (loss), Tax benefit	891	513	2,671	1,538
Net current-period other comprehensive income (loss)	1,529	871	4,588	2,613
Balance	(58,397)	(40,187)	(58,397)	(40,187)
Defined Benefit Plans | Postretirement Health Care Benefits
Accumulated other comprehensive income (loss)
Balance	(20,880)	(19,235)	(21,773)	(20,000)
Amounts reclassified from accumulated other comprehensive income (loss), Tax benefit	260	224	779	676
Net current-period other comprehensive income (loss)	447	384	1,340	1,149
Balance	(20,433)	(18,851)	(20,433)	(18,851)
Amortization of Pension and Postretirement Plan items
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	(202)	(202)	(606)	(606)
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	(202)	(202)	(606)	(606)
Actuarial losses
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	(2,925)	(1,790)	(8,772)	(5,370)
Actuarial losses | Defined Benefit Pension Plans
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	(2,218)	(1,182)	(6,653)	(3,545)
Actuarial losses | Postretirement Health Care Benefits
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	(707)	(608)	(2,119)	(1,825)
Foreign Exchange
Accumulated other comprehensive income (loss)
Balance	(5,361)	(4,273)	(3,195)	972
Other comprehensive income (loss) before classifications	(3,745)	3,381	(5,911)	(1,864)
Net current-period other comprehensive income (loss)	(3,745)	3,381	(5,911)	(1,864)
Balance	$ (9,106)	$ (892)	$ (9,106)	$ (892)