Revenues from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue from Contracts with Customers
Net revenues	$ 126,032	$ 113,114	$ 360,575	$ 313,013
Product
Revenue from Contracts with Customers
Net revenues	119,054	107,739	342,211	295,253
Aerospace
Revenue from Contracts with Customers
Net revenues	66,321	59,646	189,786	165,518
Chemical processing
Revenue from Contracts with Customers
Net revenues	21,197	21,364	61,878	55,868
Industrial gas turbine
Revenue from Contracts with Customers
Net revenues	15,870	11,866	43,638	37,042
Other markets
Revenue from Contracts with Customers
Net revenues	15,666	14,863	46,909	36,825
Other
Revenue from Contracts with Customers
Net revenues	$ 6,978	$ 5,375	$ 18,364	$ 17,760