Accounts and Financing Receivables - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Accounts Notes And Loans Receivable [Line Items]
Trade accounts receivable	$ 25,144	$ 15,776
Rental Equipment
Accounts Notes And Loans Receivable [Line Items]
Interest rate	5.00%
Term of sales-type lease	3 years
Future minimum lease payments	$ 2,900
Future minimum lease payments of unearned income	100
Single Customer
Accounts Notes And Loans Receivable [Line Items]
Trade accounts receivable	$ 8,500

Notes receivable interest rate.

No definition available.

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Namespace Prefix:	geos_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Sales type lease minimum lease payments to be received.

+ References

No definition available.

+ Details

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

- Definition

Sales type lease minimum lease payments to be received of unearned income.

+ References

No definition available.

+ Details

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Namespace Prefix:	geos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

No definition available.

+ Details

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

- Definition

Amount, before allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4531-111522

+ Details

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

- Definition

Term of lessor's sales-type 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=119202524&loc=SL77919359-209981

+ Details

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Balance Type:
Period Type: