CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 9,127	$ 3,421	$ 22,184	$ 17,836
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustments	(5,852)	(3,513)	3,793	(1,836)
Unrealized (losses) gains on marketable securities, net of tax effects of $0 during the three and six months ended March 31, 2020, and $0 during the three and six months ended March 31, 2019	(3)	232	7	111
Actuarial losses, net of tax effects $2 during the six months ended March 31, 2020, $3 during the six months ended March 31, 2019		(1)	(12)	(10)
Total other comprehensive (loss) income, net of tax	(5,855)	(3,282)	3,788	(1,735)
Comprehensive income	$ 3,272	$ 139	$ 25,972	$ 16,101