CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 14,415	$ 16,486
Other comprehensive income, net of tax:
Cumulative foreign currency translation adjustments	1,677	4,131
Unrealized gains (losses) on marketable securities, net of tax effects of ($38) and $0 during the three months ended December 31, 2018 and 2017	(121)
Actuarial gains (losses), net of tax effects of $2 and ($2) during the three months ended December 31, 2018 and 2017	(9)	(9)
Total other comprehensive income, net of tax	1,547	4,122
Comprehensive income	$ 15,962	$ 20,608