Post-employment Benefits - Benefit Accrual Activity (Details) - USD ($) $ in Thousands		12 Months Ended
	Jul. 31, 2020	Sep. 30, 2020	Sep. 30, 2019
Postemployment Benefit Liability [Roll Forward]
Balance accrued, beginning		$ 753	$ 381
Post-employment benefit charges	$ 1,100	2,280	1,727
Cash paid		(2,261)	(1,187)
Other non-cash adjustments		102	(168)
Balance accrued, ending		874	753
Employee Severance
Postemployment Benefit Liability [Roll Forward]
Balance accrued, beginning		721	372
Post-employment benefit charges		2,223	1,637
Cash paid		(2,210)	(1,159)
Other non-cash adjustments		131	(129)
Balance accrued, ending		865	721
Other Restructuring
Postemployment Benefit Liability [Roll Forward]
Balance accrued, beginning		32	9
Post-employment benefit charges		57	90
Cash paid		(51)	(28)
Other non-cash adjustments		(29)	(39)
Balance accrued, ending		$ 9	$ 32