Income Taxes - Deferred Taxes (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015
Deferred tax assets:
Pension and postretirement benefits	$ 93,238	$ 77,076
Inventories	3,405	3,771
Accrued compensation and benefits	2,264	2,027
Accrued expenses and other	3,132	2,085
Tax attributes	1,642	778
Valuation allowance	(532)	(128)
Total deferred tax assets	112,510	95,633
Deferred tax liabilities:
Property, plant and equipment, net	(41,645)	(34,109)
Intangible and other	(1,433)	(1,271)
Total deferred tax liabilities	(43,078)	(35,380)
Net deferred tax assets (liabilities)	69,432	60,253
Net current deferred tax assets		6,295
Net long-term deferred tax assets (liabilities)	69,432	53,958
Conversion Services Agreement
Deferred tax assets:
TIMET Agreement	$ 9,361	$ 10,024