Stockholder's Equity - Schedule of Non-vested Restricted Stock Units (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Jun. 30, 2021 USD ($) $ / shares shares
Time-Based Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested, Shares, Beginning balance	2,042,918
Non-vested, Shares, Granted	676,883
Non-vested, Shares, Vested	(1,006,553)
Non-vested, Shares, Forfeited	(22,844)
Non-vested, Shares, Ending balance	1,690,404
Performance-Based Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested, Shares, Beginning balance	771,387
Non-vested, Shares, Granted	290,035
Non-vested, Shares, Vested	(403,502)
Non-vested, Shares, Forfeited	(2,287)
Non-vested, Shares, Ending balance	655,633
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested, Shares, Beginning balance	2,814,305
Non-vested, Shares, Granted	966,918
Non-vested, Shares, Vested	(1,410,055)
Non-vested, Shares, Forfeited	(25,131)
Non-vested, Shares, Ending balance	2,346,037
Non-vested, Shares, Expected to vest	2,346,037
Non-vested, Weighted-Average Grant-Date Fair Value, Beginning balance | $ / shares	$ 18.63
Non-vested, Weighted-Average Grant-Date Fair Value, Granted | $ / shares	61.32
Non-vested, Weighted-Average Grant-Date Fair Value, Vested | $ / shares	37.85
Non-vested, Weighted-Average Grant-Date Fair Value, Forfeited | $ / shares	45.21
Non-vested, Weighted-Average Grant-Date Fair Value, Ending balance | $ / shares	42.34
Non-vested, Weighted-Average Grant-Date Fair Value, Expected to vest | $ / shares	$ 42.34
Non-vested, Weighted-Average Remaining Contractual Term (years), Balance	1 year 2 months 26 days
Non-vested, Weighted-Average Remaining Contractual Term (years), Expected to vest	1 year 2 months 26 days
Non-vested, Aggregate Intrinsic Value, Balance | $	$ 250,322
Non-vested, Aggregate Intrinsic Value, Expected to vest | $	$ 250,322