Restructuring and Other Charges - Activity Related to Restructuring Accruals (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Restructuring Reserve [Roll Forward]
Beginning Balance	$ 5,939	$ 2,073	$ 3,475
Expenses	3,226	12,039	4,713
Expenses, fiscal year 2015			4,417
Payments	(7,457)	(8,173)	(5,819)
Ending Balance	1,708	5,939	2,073
Facilities and other contract termination costs
Restructuring Reserve [Roll Forward]
Beginning Balance	0	433	71
Expenses		25	1,300
Expenses, fiscal year 2015			1,204
Payments		(458)	(842)
Ending Balance		0	433
Workforce-related termination benefits
Restructuring Reserve [Roll Forward]
Beginning Balance	5,939	1,640	3,404
Expenses	3,226	12,014	3,400
Expenses, fiscal year 2015			3,213
Payments	(7,457)	(7,715)	(4,977)
Ending Balance	$ 1,708	$ 5,939	$ 1,640