Comprehensive Income (Loss) and Changes in Accumulated Other Comprehensive Income (Loss) by Component - Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Comprehensive Income (Loss)
Net income	$ 3,162	$ 2,792	$ (1,162)	$ 228	$ 5,784	$ 6,602	$ 11,719	$ 6,381	$ 5,020	$ 30,486	$ 3,751
Other comprehensive income (loss), Pre-tax									(37,771)	(38,650)	(7,398)
Other comprehensive income (loss), Tax									11,201	12,525	2,369
Other comprehensive loss									(26,570)	(26,125)	(5,029)
Comprehensive income (loss)									(21,550)	4,361	(1,278)
Pension and postretirement: Net gain (loss) arising during period
Comprehensive Income (Loss)
Other comprehensive income (loss), Pre-tax									(18,299)	(26,515)	(1,886)
Other comprehensive income (loss), Tax									6,609	9,595	698
Other comprehensive loss									(11,690)	(16,920)	(1,188)
Pension and postretirement: Less: amortization of prior service cost
Comprehensive Income (Loss)
Other comprehensive income (loss), Pre-tax									(808)	(808)	2,087
Other comprehensive income (loss), Tax									299	298	(773)
Other comprehensive loss									(509)	(510)	1,314
Pension and postretirement: Less: amortization of gain (loss)
Comprehensive Income (Loss)
Other comprehensive income (loss), Pre-tax									(11,663)	(7,160)	(6,608)
Other comprehensive income (loss), Tax									4,293	2,632	2,444
Other comprehensive loss									(7,370)	(4,528)	(4,164)
Accumulated Translation Adjustment
Comprehensive Income (Loss)
Other comprehensive income (loss), Pre-tax									(7,001)	(4,167)	(991)
Other comprehensive loss									$ (7,001)	$ (4,167)	$ (991)