Equity-Based Compensation - Schedule of Total Equity-Based Compensation Expense (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Total equity-based compensation expense recognized	[1]	$ 14,951	$ 2,193	$ 20,753	$ 2,637

[1] Represents equity-based compensation expense recognized for equity incentive plans outstanding.