Segment and Geographic Information - Revenue By Geographic Segment (Parenthetical) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Total revenue	$ 1,458,415	$ 1,255,631	$ 1,241,824
Calculated under Revenue Guidance in Effect before Topic 606
Total revenue		1,311,494	1,241,824
United States
Total revenue	621,800	514,400	487,300
United States | Calculated under Revenue Guidance in Effect before Topic 606
Total revenue		541,700
Germany
Total revenue	$ 198,700	185,400	$ 193,300
Germany | Calculated under Revenue Guidance in Effect before Topic 606
Total revenue		$ 197,200