Income Taxes - Components of Income Tax Provision (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Current:
Federal	$ 11,294	$ 1,542	$ (5,856)
State	1,020	(198)	1,105
Foreign	22,855	23,177	23,196
Current tax provision (benefit)	35,169	24,521	18,445
Deferred:
Federal	(10,931)	(83,319)	7,291
State	1,477	2,302	1,133
Foreign	(114,309)	(5,824)	(3,198)
Deferred tax (benefit) provision	(123,763)	(86,841)	5,226
(Benefit) provision for income taxes	$ (88,594)	$ (62,320)	$ 23,671
Effective tax rate	(344.10%)	25.20%	(15.30%)
TCJA
Current:
Current tax provision (benefit)	$ 5,800
Deferred:
Deferred tax (benefit) provision	$ 92,900