Income Taxes - Components of income (loss) and provision for income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Components of income (loss) before income taxes
United States	$ (51,049)	$ (70,566)	$ (76,136)
Foreign	65,935	59,484	49,699
Income (loss) from continuing operations before income taxes	14,886	(11,082)	(26,437)
Current:
Federal	(4,775)	(4,070)	(1,679)
State	976	878	(618)
Foreign	19,882	13,869	8,249
Total current	16,083	10,677	5,952
Deferred:
Federal	(7,874)	2,257	(16,256)
State	482	569	(4,333)
Foreign	(1,598)	1,155	280
Total deferred	(8,990)	3,981	(20,309)
Provision for income taxes	$ 7,093	$ 14,658	$ (14,357)