Stock-Based Compensation - Stock Option Activity (Details) - Stock options - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021
Options Outstanding, Number of Shares
Balance at the beginning of the period	765
Options granted	0	0
Options exercised	(151)
Balance at the end of the period	614		765
Options Outstanding, Weighted average exercise price
Balance at the beginning of the period (in dollars per share)	$ 16.06
Options exercised (in dollars per share)	9.46
Balance at the end of the period (in dollars per share)	$ 17.69		$ 16.06
Options Additional Disclosures
Weighted average remaining contractual term	2 years 3 months 18 days		2 years 4 months 24 days
Weighted average remaining contractual term of options vested and exercisable at the end of the year (years)	2 years 3 months 18 days
Aggregate intrinsic value at the beginning of the period	$ 133,550
Aggregate intrinsic value at the end of the period	$ 161,112		$ 133,550
Options vested and exercisable at the end of the period (in shares)	614
Options vested and exercisable at the end of the period, weighted average exercise price (in dollars per share)	$ 17.69
Options vested and exercisable intrinsic value	$ 161,112
Total intrinsic value of options exercised	$ 35,868	$ 11,408