Income Taxes- Summary of Income Tax Benefit and Effective Income Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income (loss) before income taxes	$ 42,742	$ (150)	$ 25,858	$ (62,289)
Income tax expense (benefit)	$ 11,033	$ 1,247	$ 6,582	$ (58,150)
Effective income tax rate	25.80%		25.50%	93.40%