Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Accumulated other comprehensive income (loss)
Balance	$ 311,299
Other comprehensive income (loss)	(446)	$ 288
Balance	307,721
AOCI Attributable to Parent
Accumulated other comprehensive income (loss)
Balance	(114,523)	(87,953)
Other comprehensive loss before reclassifications	(3,026)	(1,688)
Amounts reclassified from accumulated other comprehensive income (loss), Tax benefit	(1,502)	(1,150)
Other comprehensive income (loss)	(446)	288
Balance	(114,969)	(87,665)
Accumulated Defined Benefit Plans Adjustment | Defined Benefit Pension Plans
Accumulated other comprehensive income (loss)
Balance	(74,742)	(62,985)
Amounts reclassified from accumulated other comprehensive income (loss), Tax benefit	(1,108)	(890)
Other comprehensive income (loss)	1,904	1,530
Balance	(72,838)	(61,455)
Accumulated Defined Benefit Plans Adjustment | Postretirement Health Care Benefits
Accumulated other comprehensive income (loss)
Balance	(29,585)	(21,773)
Amounts reclassified from accumulated other comprehensive income (loss), Tax benefit	(394)	(260)
Other comprehensive income (loss)	676	446
Balance	(28,909)	(21,327)
Amortization of Pension and Postretirement Plan items
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	202	202
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
Actuarial losses
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	3,880	2,924
Actuarial losses | Defined Benefit Pension Plans
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	2,810	2,218
Actuarial losses | Postretirement Health Care Benefits
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	1,070	706
Accumulated Translation Adjustment
Accumulated other comprehensive income (loss)
Balance	(10,196)	(3,195)
Other comprehensive loss before reclassifications	(3,026)	(1,688)
Other comprehensive income (loss)	(3,026)	(1,688)
Balance	$ (13,222)	$ (4,883)