Accumulated Other Comprehensive Income Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Beginning Balance	$ 244,467	$ 289,624	$ 329,258
Other comprehensive income (loss)	1,711	(2,996)	(10,449)
Ending Balance	195,154	244,467	289,624
Unrealized Gains (Losses) on Available-for-Sale Securities
Beginning Balance	(15)	(3)	(26)
Other comprehensive income (loss)	(43)	(12)	23
Ending Balance	(58)	(15)	(3)
Foreign Currency Translation Adjustments
Beginning Balance	(15,926)	(12,942)	(2,470)
Other comprehensive income (loss)	1,754	(2,984)	(10,472)
Ending Balance	(14,172)	(15,926)	(12,942)
Accumulated Other Comprehensive Loss
Beginning Balance	(15,941)	(12,945)	(2,496)
Other comprehensive income (loss)	1,711	(2,996)	(10,449)
Ending Balance	$ (14,230)	$ (15,941)	$ (12,945)