Restructuring and Other Costs, Net - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring charges (reversal)	$ 18,237	$ 24,404	$ 12,863
Severance Charge
Restructuring Cost And Reserve [Line Items]
Restructuring charges (reversal)	3,694	130	4,130
Facilities Restructuring
Restructuring Cost And Reserve [Line Items]
Restructuring charges (reversal)	2,816	1,704	20
Professional Services Fees
Restructuring Cost And Reserve [Line Items]
Restructuring charges (reversal)	$ 11,727	$ 22,570	$ 8,713