Comprehensive Income (Loss) and Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Accumulated other comprehensive income (loss).
Balance	$ 346,730	$ 355,803	$ 301,098
Amortization of Pension and Postretirement Plan items	(808)	2,087	4,981
Actuarial losses	(7,160)	(6,608)	(13,906)
Tax expense or (benefit)	16,690	1,369	10,421
Net current-period other comprehensive income (loss)	(26,125)	(5,029)	42,292
Balance	341,989	346,730	355,803
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss).
Balance	(61,828)	(56,799)	(99,091)
Other comprehensive loss before classifications	(31,163)	(7,879)
Net current-period other comprehensive income (loss)	(26,125)	(5,029)	42,292
Balance	(87,953)	(61,828)	(56,799)
Accumulated Defined Benefit Plans Adjustment | Pension Plan, Defined Benefit
Accumulated other comprehensive income (loss).
Balance	(42,800)	(42,798)
Other comprehensive loss before classifications	(23,688)	(3,418)
Net current-period other comprehensive income (loss)	(20,185)	(2)
Balance	(62,985)	(42,800)	(42,798)
Accumulated Defined Benefit Plans Adjustment | Postretirement health care
Accumulated other comprehensive income (loss).
Balance	(20,000)	(15,964)
Other comprehensive loss before classifications	(3,308)	(3,470)
Net current-period other comprehensive income (loss)	(1,773)	(4,036)
Balance	(21,773)	(20,000)	(15,964)
Accumulated Translation Adjustment
Accumulated other comprehensive income (loss).
Balance	972	1,963
Other comprehensive loss before classifications	(4,167)	(991)
Net current-period other comprehensive income (loss)	(4,167)	(991)
Balance	(3,195)	972	$ 1,963
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss).
Amortization of Pension and Postretirement Plan items	808	(2,087)
Actuarial losses	7,160	6,609
Tax expense or (benefit)	(2,930)	(1,672)
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment | Pension Plan, Defined Benefit
Accumulated other comprehensive income (loss).
Amortization of Pension and Postretirement Plan items	808	808
Actuarial losses	4,726	4,613
Tax expense or (benefit)	(2,031)	(2,005)
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment | Postretirement health care
Accumulated other comprehensive income (loss).
Amortization of Pension and Postretirement Plan items		(2,895)
Actuarial losses	2,434	1,996
Tax expense or (benefit)	$ (899)	$ 333