Concentration of Credit Risk - External net revenue, net of intercompany eliminations, and net asset information by region (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Oct. 01, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 1,429,456	$ 1,444,441	$ 1,339,541
Net Assets	482,063	365,822
Property, plant, and equipment, net	364,461	333,584		$ 336,396
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	1,164,634	1,147,649	1,067,636
Net Assets	408,330	324,887
Property, plant, and equipment, net	347,832	304,088
Rest of World
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	264,822	296,792	$ 271,905
Net Assets	73,733	40,935
Property, plant, and equipment, net	$ 16,629	$ 29,496