Leases - Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Operating	$ 890	$ 1,253	$ 1,860	$ 2,565
Short-term	42	47	71	103
Variable	25	3	30	23
Sublease income	(92)	(79)	(187)	(128)
Total lease costs	$ 865	$ 1,224	$ 1,774	$ 2,563