Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (66,655)	$ (9,356)	$ 941	$ 11,074
Other comprehensive income (loss):
Foreign currency translation adjustment	(2,028)	813	(1,971)	(839)
Total other comprehensive income (loss)	(2,028)	813	(1,971)	(839)
Comprehensive income (loss)	$ (68,683)	$ (8,543)	$ (1,030)	$ 10,235