Restructuring and Other Charges - Activity Related to Restructuring Accruals (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Restructuring Reserve [Roll Forward]
Beginning Balance	$ 1,708	$ 5,939	$ 2,073
Expenses	714	3,144	10,210
Payments	(1,763)	(7,375)	(6,344)
Ending Balance	659	1,708	5,939
Facilities and other contract termination costs
Restructuring Reserve [Roll Forward]
Beginning Balance			433
Expenses			25
Payments			(458)
Ending Balance
Workforce-related termination benefits
Restructuring Reserve [Roll Forward]
Beginning Balance	1,708	5,939	1,640
Expenses	714	3,144	10,185
Payments	(1,763)	(7,375)	(5,886)
Ending Balance	$ 659	$ 1,708	$ 5,939