Equity Method Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017
Schedule of Equity Method Investments [Line Items]
Equity method investment	$ 35,134		$ 35,134		$ 28,593
Equity in earnings of equity method investments	$ 1,422	$ 2,777	$ 3,602	$ 4,719
ULVAC Cryogenics, Inc.
Schedule of Equity Method Investments [Line Items]
Joint venture interest (as a percent)	50.00%		50.00%
Equity method investment	$ 35,100		$ 35,100		$ 28,600
Equity in earnings of equity method investments	1,400	2,800	3,600	5,200
Management fee payments received	$ 300	$ 200	$ 500	$ 500