Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Current:
Federal	$ 1,299	$ 8,071	$ 19,576
State	(423)	2,236	1,055
Foreign	15,371	9,559	8,486
Current income tax	16,247	19,866	29,117
Deferred:
Federal	7,003	13,987	(8,523)
State	947	132	(296)
Foreign	(249)	(3,535)	2,571
Deferred income taxes	7,701	10,584	(6,248)
Total provision	$ 23,948	$ 30,450	$ 22,869