Revenue Recognition - Additional Information (Details) - USD ($)	3 Months Ended	6 Months Ended
Mar. 31, 2019	Mar. 31, 2019	Oct. 01, 2018
Disaggregation of Revenue [Line Items]
Revenue recognized included in contract liability balance at the beginning of the period		$ 3,600,000
Impairment losses recognized on capitalized contract costs	$ 0	0
Selling and marketing
Disaggregation of Revenue [Line Items]
Amortization of capitalized contract costs	100,000	200,000
Other Current and Non-current Assets
Disaggregation of Revenue [Line Items]
Capitalized contract costs	$ 1,400,000	$ 1,400,000	$ 1,000,000.0

Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054

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Amount of impairment loss for asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

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Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer; classified as current.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054

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Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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