Income Taxes- Summary of Income Tax Benefit and Effective Income Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Loss before income taxes	$ (4,921)	$ (29,922)	$ (16,884)	$ (62,137)
Income tax (benefit)	$ (1,315)	$ (7,858)	$ (4,451)	$ (59,397)
Effective income tax rate	26.70%	26.30%	26.40%	95.60%