Revenue Recognition - Schedule of Contract Asset and Contract Liabilities (Details) $ in Thousands	6 Months Ended
Mar. 31, 2025 USD ($)
Disaggregation of Revenue [Line Items]
Balance as of September 30, 2024	$ 5,618
New performance obligations	17,392
Recognition of revenue as a result of satisfying performance obligations	(8,666)
Effect of exchange rate on deferred revenue	(3)
Balance as of March 31, 2035	14,341
Less: non-current portion	(287)
Current portion as of March 31, 2035	14,054
Customer Deposits [Member]
Disaggregation of Revenue [Line Items]
Balance as of September 30, 2024	1,606
New performance obligations	13,385
Recognition of revenue as a result of satisfying performance obligations	(4,094)
Balance as of March 31, 2035	10,897
Current portion as of March 31, 2035	10,897
Deferred Revenue [Member]
Disaggregation of Revenue [Line Items]
Balance as of September 30, 2024	4,012
New performance obligations	4,007
Recognition of revenue as a result of satisfying performance obligations	(4,572)
Effect of exchange rate on deferred revenue	(3)
Balance as of March 31, 2035	3,444
Less: non-current portion	(287)
Current portion as of March 31, 2035	$ 3,157

Represents effect of exchange rate for contract with customer liability.

No definition available.

Name:	gnss_ContractWithCustomerLiabilityEffectOfExchangeRate
Namespace Prefix:	gnss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of increase in obligation to transfer good or service to customer for which consideration from customer has been received or is due, from new contract.

+ References

No definition available.

+ Details

Name:	gnss_ContractWithCustomerLiabilityIncreaseForNewContract
Namespace Prefix:	gnss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of revenue recognized during period including amounts 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

No definition available.

+ Details

Name:	gnss_ContractWithCustomerLiabilityRevenueRecognizedDuringPeriod
Namespace Prefix:	gnss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-8

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-2

+ Details

Name:	us-gaap_ContractWithCustomerLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

+ References

+ Details

Name:	us-gaap_ContractWithCustomerLiabilityCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as noncurrent.

+ References

+ Details

Name:	us-gaap_ContractWithCustomerLiabilityNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-5

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

+ Details

Name:	us-gaap_DisaggregationOfRevenueLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=gnss_CustomerDepositsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=gnss_DeferredRevenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: