Income Taxes - Components of income (loss) and provision for income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Components of income (loss) before income taxes
United States	$ (535)	$ (51,049)	$ (70,566)
Foreign	52,881	65,935	59,484
Income (loss) from continuing operations before income taxes	52,346	14,886	(11,082)
Current:
Federal	(710)	(4,775)	(4,070)
State	2,898	976	878
Foreign	10,523	19,882	13,869
Total current	12,711	16,083	10,677
Deferred:
Federal	(4,553)	(7,874)	2,257
State	(135)	482	569
Foreign	3,017	(1,598)	1,155
Total deferred	(1,671)	(8,990)	3,981
Provision for income taxes	$ 11,040	$ 7,093	$ 14,658