Leases.

No definition available.

Name:	geos_LeasesLineItems
Namespace Prefix:	geos_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of operating right-of use asset related to leased facility.

+ References

No definition available.

+ Details

Name:	geos_NumberOfOperatingRightOfUseAssetRelatedToLeasedFacility
Namespace Prefix:	geos_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Trade accounts receivables included lease receivables.

+ References

No definition available.

+ Details

Name:	geos_TradeAccountsReceivablesIncludedLeaseReceivables
Namespace Prefix:	geos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of lease payments to be received by lessor for operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=121576215&loc=SL77919396-209981

+ Details

Name:	us-gaap_LessorOperatingLeasePaymentsToBeReceived
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Term of lessor's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=121576215&loc=SL77919359-209981

+ Details

Name:	us-gaap_LessorOperatingLeaseTermOfContract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

The total amount of revenue recognized for the period from operating leases, including minimum lease revenue, contingent revenue, percentage revenue and sublease revenue.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121549951&loc=d3e39896-112707

+ Details

Name:	us-gaap_OperatingLeasesIncomeStatementLeaseRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=stpr_TX
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Leases - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
Leases - Additional Information (Details) $ in Thousands	Jun. 30, 2021 USD ($) OperatingRightOfUseAsset	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) OperatingRightOfUseAsset	Jun. 30, 2020 USD ($)
Leases [Line Items]
Trade accounts receivables included lease receivables	$ 4,800		$ 4,800
Rental revenue	5,404	$ 15,728	9,430	$ 40,740
Future minimum lease payments to be received	$ 6,400		$ 6,400
Maximum
Leases [Line Items]
Lease term	6 months		6 months
Austin, Texas
Leases [Line Items]
Number of operating right-of use asset related to leased facility \| OperatingRightOfUseAsset	2		2