Discontinued Operations - Financial Results (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent, Total	$ 6,250	$ 4,523	$ 14,399	$ 19,390
Discontinued Operations, Held-for-sale | Semiconductor Cryogenics Business
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total revenue	35,654	50,308	74,978	97,037
Total cost of revenue	21,860	28,009	44,425	53,782
Gross profit	13,794	22,299	30,553	43,255
Research and development	2,168	1,620	4,326	3,414
Selling, general and administrative	4,993	7,180	12,196	10,427
Restructuring charges		2		2
Total operating expenses	7,161	8,802	16,522	13,843
Operating income	6,633	13,497	14,031	29,412
Other income, net	278	255	567	527
Income before income taxes and earnings of equity method investment	6,911	13,752	14,598	29,939
Income tax provision	1,930	10,651	3,240	14,151
Income before equity in earnings of equity method investment	4,981	3,101	11,358	15,788
Equity in earnings of equity method investment	1,269	1,422	3,041	3,602
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent, Total	6,250	4,523	14,399	19,390
Discontinued Operations, Held-for-sale | Semiconductor Cryogenics Business | Products
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total revenue	23,895	39,460	52,681	75,872
Total cost of revenue	15,182	22,499	31,698	43,147
Discontinued Operations, Held-for-sale | Semiconductor Cryogenics Business | Services
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total revenue	11,759	10,848	22,297	21,165
Total cost of revenue	$ 6,678	$ 5,510	$ 12,727	$ 10,635