Restructuring Costs - Rollforward of Restructuring Liability (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Restructuring liability
Accrued costs	$ 4,135	$ 1,575
Employee Separation and other
Restructuring liability
Balance as of the beginning of the period	5,200
Accrued costs	4,100
Cash payments	(5,200)
Balance as of the end of the period	4,100
Consulting Costs
Restructuring liability
Balance as of the beginning of the period	800
Cash payments	$ (800)