Stockholders' Equity - RSU Activity (Details) - RSUs - $ / shares	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Number of Shares
Beginning balance (in shares)	2,352,487	2,580,176	2,357,021
Granted (in shares)	1,394,869	1,147,976	1,184,906
Settled (in shares)	(818,665)	(881,420)	(745,197)
Canceled (in shares)	(266,748)	(494,245)	(216,554)
Ending balance (in shares)	2,661,943	2,352,487	2,580,176
Weighted- Average Fair Value Per Share
Beginning balance (in dollars per share)	$ 8.26	$ 6.92	$ 5.65
Granted (in dollars per share)	7.39	9.67	8.54
Settled (in dollars per share)	7.82	6.53	5.26
Canceled (in dollars per share)	8.26	7.70	7.39
Ending balance (in dollars per share)	$ 7.95	$ 8.26	$ 6.92

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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Number of non-option equity instruments exercised by participants.

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Number of shares under non-option equity instrument agreements that were cancelled as a result of occurrence of a terminating event.

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Net number of non-option equity instruments granted to participants.

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Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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