Revenues from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue from Contracts with Customers
Net revenues	$ 80,576	$ 126,032	$ 300,592	$ 360,575
Product
Revenue from Contracts with Customers
Net revenues	77,394	119,054	283,054	342,211
Aerospace
Revenue from Contracts with Customers
Net revenues	40,375	66,321	158,390	189,786
Chemical processing
Revenue from Contracts with Customers
Net revenues	12,143	21,197	44,687	61,878
Industrial gas turbine
Revenue from Contracts with Customers
Net revenues	13,673	15,870	44,137	43,638
Other markets
Revenue from Contracts with Customers
Net revenues	11,203	15,666	35,840	46,909
Other
Revenue from Contracts with Customers
Net revenues	$ 3,182	$ 6,978	$ 17,538	$ 18,364