Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 30,987	$ 49,375	$ (37,992)	$ 50,316
Other comprehensive income (loss):
Foreign currency translation adjustment	1,542	(1,535)	(848)	(3,506)
Total other comprehensive income (loss)	1,542	(1,535)	(848)	(3,506)
Comprehensive income (loss)	$ 32,529	$ 47,840	$ (38,840)	$ 46,810