Income Taxes - Provision (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Income tax expense (benefit)	$ (4,680)	$ (1,550)
Benefit related to stock compensation windfalls	$ 4,800	$ 1,900