UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net income	$ 35,171	$ 19,939	$ 61,825	$ 60,450
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(8,829)	(2,635)	2,276	(6,326)
Net unrealized gain (loss) on available-for-sale securities	(48)	0	(48)	0
Net unrealized gain (loss) on cash flow hedges	(210)	1	(63)	819
Other comprehensive income (loss), net of tax	(9,087)	(2,634)	2,165	(5,507)
Comprehensive income	$ 26,084	$ 17,305	$ 63,990	$ 54,943