Revenues from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Revenue from Contracts with Customers
Net revenues	$ 111,563	$ 127,474	$ 220,016	$ 234,543
Product
Revenue from Contracts with Customers
Net revenues	104,467	121,262	205,660	223,157
Aerospace
Revenue from Contracts with Customers
Net revenues	59,172	68,858	118,015	123,465
Chemical processing
Revenue from Contracts with Customers
Net revenues	15,832	21,761	32,544	40,681
Industrial gas turbine
Revenue from Contracts with Customers
Net revenues	16,701	13,685	30,464	27,768
Other markets
Revenue from Contracts with Customers
Net revenues	12,762	16,958	24,637	31,243
Other
Revenue from Contracts with Customers
Net revenues	$ 7,096	$ 6,212	$ 14,356	$ 11,386