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Stock-Based Compensation - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2022	Mar. 18, 2021
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 17.0	$ 21.5
Share-based payment award (in shares)	3,964,181		4,069,431
Unrecognized pre-tax compensation expense	$ 128.3
Weighted average period to recognize pre-tax compensation expense	2 years 2 months 12 days
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of options exercised	$ 2.3	12.5
Stock-based compensation expense	2.4	$ 3.0
Unrecognized pre-tax compensation expense	$ 9.5
Weighted average period to recognize pre-tax compensation expense	1 year 3 months 18 days
2004 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance (in shares)	175,083
2004 Equity Incentive Plan \| Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	0
2013 Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance (in shares)	3,991,304
Number of shares forfeited (in shares)	136,972
2013 Incentive Plan \| Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	2,305,761
2021 Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)	7,155,527			8,000,000
2021 Incentive Plan \| Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	918,795
Inducement Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance (in shares)	762,150
Inducement Awards \| Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance (in shares)	739,625
Share-based payment award (in shares)	739,625