Discontinued Operations - Financial Results (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Net income	$ 427,862	$ 48,747	$ 51,925
Discontinued Operations, Held-for-sale | Semiconductor Cryogenics Business
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total revenue	109,518	196,096	165,386
Total cost of revenue	66,164	108,184	96,114
Gross profit	43,354	87,912	69,272
Research and development	6,605	7,605	6,860
Selling, general and administrative	20,889	25,017	12,536
Restructuring charges	24	2	82
Total operating expenses	27,518	32,624	19,478
Operating income	15,836	55,288	49,794
Other income, net	539,948	1,091	1,057
Income before income taxes and earnings of equity method investment	555,784	56,379	50,851
Income tax provision	134,110	14,420	8,760
Income before equity in earnings of equity method investment	421,674	41,959	42,091
Equity in earnings of equity method investment	6,188	6,788	9,834
Net income	427,862	48,747	51,925
Discontinued Operations, Held-for-sale | Semiconductor Cryogenics Business | Products
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total revenue	76,227	150,365	126,638
Total cost of revenue	47,148	85,350	73,714
Discontinued Operations, Held-for-sale | Semiconductor Cryogenics Business | Services
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total revenue	33,291	45,731	38,748
Total cost of revenue	$ 19,016	$ 22,834	$ 22,400