Stock Award Plans - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Number of Options
Outstanding, beginning balance (in shares)	320,287	51,060
Granted (in shares)	1,043,349	356,343	0
Exercised (in shares)	(8,085)	(22,975)
Forfeited (in shares)	(125,827)	(64,141)
Outstanding, ending balance (in shares)	1,229,724	320,287	51,060
Exercisable (in shares)	19,535
Weighted Average Exercise Price
Outstanding, beginning balance (in dollars per share)	$ 27.21	$ 15.25
Granted (in dollars per share)	29.53	28.16
Exercised (in dollars per share)	17.88	12.99
Forfeited (in dollars per share)	30.25	27.96
Outstanding, ending balance (in dollars per share)	28.93	$ 27.21	$ 15.25
Exercisable (in dollars per share)	$ 16.88
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options outstanding, weighted average remaining contractual term (in years)	9 years	8 years	2 years
Options exercisable, weighted average remaining contractual term (in years)	6 months
Options outstanding, aggregate intrinsic value	$ 0	$ 3,136	$ 855
Options exercisable, aggregate intrinsic value	$ 78
Stock Option Awards
Number of Options
Granted (in shares)	1,043,349

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Number of share options (or share units) exercised during the current period.

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