Discontinued Operations - Financial Results (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Net income	$ 6,333	$ 17,793	$ 20,731	$ 37,183
Discontinued Operations, Held-for-sale | Semiconductor Cryogenics Business
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total revenue	34,540	51,117	109,518	148,154
Total cost of revenue	21,739	28,520	66,164	82,302
Gross profit	12,801	22,597	43,354	65,852
Research and development	2,279	2,073	6,605	5,483
Selling, general and administrative	4,808	6,392	17,005	16,823
Restructuring charges	24		24	2
Total operating expenses	7,111	8,465	23,634	22,308
Operating income	5,690	14,132	19,720	43,544
Other income, net	418	292	985	819
Income before income taxes and earnings of equity method investment	6,108	14,424	20,705	44,363
Income tax provision (benefit)	1,610	(2,040)	4,850	12,111
Income before equity in earnings of equity method investment	4,498	16,464	15,855	32,252
Equity in earnings of equity method investment	1,835	1,329	4,876	4,931
Net income	6,333	17,793	20,731	37,183
Discontinued Operations, Held-for-sale | Semiconductor Cryogenics Business | Products
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total revenue	23,546	38,834	76,227	114,706
Total cost of revenue	15,451	22,289	47,148	65,436
Discontinued Operations, Held-for-sale | Semiconductor Cryogenics Business | Services
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total revenue	10,994	12,283	33,291	33,448
Total cost of revenue	$ 6,288	$ 6,231	$ 19,016	$ 16,866