Restructuring and Other Charges, Net - Accrual Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Restructuring Reserve [Roll Forward]
Beginning balance	$ 17,057	$ 9,743	$ 12,474
Restructuring and other charges, net	23,302	35,408	18,901
Non-cash adjustment	(102)	(998)	(1,374)
Cash payments	(32,652)	(27,096)	(20,258)
Ending balance	7,605	17,057	9,743
Personnel
Restructuring Reserve [Roll Forward]
Beginning balance	10,556	1,474	2,599
Restructuring and other charges, net	19,371	31,520	12,553
Non-cash adjustment	0	0	0
Cash payments	(25,971)	(22,438)	(13,678)
Ending balance	3,956	10,556	1,474
Facilities
Restructuring Reserve [Roll Forward]
Beginning balance	6,501	8,269	9,875
Restructuring and other charges, net	3,931	3,888	6,348
Non-cash adjustment	(102)	(998)	(1,374)
Cash payments	(6,681)	(4,658)	(6,580)
Ending balance	$ 3,649	$ 6,501	$ 8,269