Comprehensive Income (Loss) and Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Net income	$ 5,784	$ 6,602	$ 11,719	$ 6,381	$ 6,370	$ 2,096	$ (1,223)	$ (3,492)	$ 30,486	$ 3,751	$ 21,577
Pension and postretirement:
Net gain (loss) arising during period									(26,515)	(1,886)	74,282
Less: amortization of prior service cost									(808)	2,087	4,981
Less: amortization of gain (loss)									(7,160)	(6,608)	(13,906)
Foreign currency translation adjustment									(4,167)	(991)	1,012
Other comprehensive income (loss)									(38,650)	(7,398)	66,369
Pension and postretirement:
Net gain (loss) arising during period									9,595	698	(27,201)
Less: amortization of prior service cost									298	(773)	(1,743)
Less: amortization of gain (loss)									2,632	2,444	4,867
Other comprehensive income (loss)									12,525	2,369	(24,077)
Pension and postretirement:
Net gain (loss) arising during period									(16,920)	(1,188)	47,081
Less: amortization of prior service cost									(510)	1,314	3,238
Less: amortization of gain (loss)									(4,528)	(4,164)	(9,039)
Foreign currency translation adjustment									(4,167)	(991)	1,012
Other comprehensive income (loss)									(26,125)	(5,029)	42,292
Comprehensive income (loss)									$ 4,361	$ (1,278)	$ 63,869