Income Taxes - Components of income (loss) and provision for income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Components of income (loss) before income taxes
United States	$ (66,358)	$ (535)	$ (51,049)
Foreign	62,913	52,881	65,935
Income (loss) from continuing operations before income taxes	(3,445)	52,346	14,886
Current:
Federal	(3,082)	(710)	(4,775)
State	2,297	2,898	976
Foreign	9,565	10,523	19,882
Total current	8,780	12,711	16,083
Deferred:
Federal	(10,733)	(4,553)	(7,874)
State	(6,960)	(135)	482
Foreign	2,533	3,017	(1,598)
Total deferred	(15,160)	(1,671)	(8,990)
Provision (benefit) for income taxes	$ (6,380)	$ 11,040	$ 7,093