Income Taxes - Deferred Taxes (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Deferred tax assets:
Pension and postretirement benefits	$ 48,367	$ 38,343
Inventories	1,706	2,091
Accrued compensation and benefits	770	1,387
Accrued expenses and other	3,308	2,977
Tax attributes	4,441	4,178
Valuation allowance	(1,675)	(1,661)
Total deferred tax assets	61,080	52,090
Deferred tax liabilities:
Property, plant and equipment, net	(27,873)	(27,521)
Intangible and other	(1,091)	(1,034)
Total deferred tax liabilities	(28,964)	(28,555)
Net deferred tax assets (liabilities)	32,116	23,535
Conversion Services Agreement
Deferred tax assets:
TIMET Agreement	$ 4,163	$ 4,775