Discontinued Operations - Financial Results (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Net income (loss)	$ 48,747	$ 51,925	$ 15,981
Semiconductor Cryogenics Business | Held-for-sale
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total revenue	196,096	165,386	126,311
Total cost of revenue	108,184	96,114	84,118
Gross profit	87,912	69,272	42,193
Research and development	7,605	6,860	6,932
Selling, general and administrative	25,017	12,536	12,139
Restructuring charges	2	82	1,830
Total operating expenses	32,624	19,478	20,901
Operating income	55,288	49,794	21,292
Other (expense) income, net	1,091	1,057	804
Income before income taxes and earnings of equity method investment	56,379	50,851	22,096
Income tax provision	14,420	8,760	9,560
Income before equity in earnings of equity method investment	41,959	42,091	12,536
Equity in earnings (losses) of equity method investment	6,788	9,834	3,445
Net income (loss)	48,747	51,925	15,981
Semiconductor Cryogenics Business | Held-for-sale | Products
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total revenue	150,365	126,638	85,860
Total cost of revenue	85,350	73,714	55,144
Semiconductor Cryogenics Business | Held-for-sale | Services
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total revenue	45,731	38,748	40,451
Total cost of revenue	$ 22,834	$ 22,400	$ 28,974