Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 3,725	$ 5,240	$ 12,348	$ 14,537
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	3,348	4,881	11,361	13,764
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 377	$ 359	$ 987	$ 773