Stockholder's Equity - Schedule of Non-vested Restricted Stock Units (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Mar. 31, 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	652,976
Non-vested, Shares, Vested	(955,286)
Non-vested, Shares, Forfeited	(19,826)
Non-vested, Shares, Ending balance	1,720,782
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	943,011
Non-vested, Shares, Vested	(1,358,788)
Non-vested, Shares, Forfeited	(22,113)
Non-vested, Shares, Ending balance	2,376,415
Non-vested, Shares, Expected to vest	2,376,415
Non-vested, Weighted-Average Grant-Date Fair Value, Beginning balance | $ / shares	$ 18.63
Non-vested, Weighted-Average Grant-Date Fair Value, Granted | $ / shares	59.65
Non-vested, Weighted-Average Grant-Date Fair Value, Vested | $ / shares	38.33
Non-vested, Weighted-Average Grant-Date Fair Value, Forfeited | $ / shares	31.42
Non-vested, Weighted-Average Grant-Date Fair Value, Ending balance | $ / shares	40.08
Non-vested, Weighted-Average Grant-Date Fair Value, Expected to vest | $ / shares	$ 40.08
Non-vested, Weighted-Average Remaining Contractual Term (years), Balance	1 year 2 months 12 days
Non-vested, Weighted-Average Remaining Contractual Term (years), Expected to vest	1 year 2 months 12 days
Non-vested, Aggregate Intrinsic Value, Balance | $	$ 212,855
Non-vested, Aggregate Intrinsic Value, Expected to vest | $	$ 212,855