XML 51 R38.htm IDEA: XBRL DOCUMENT
v3.19.1

Short-term Investments - Additional Information (Details) | 6 Months Ended
--- | ---
Mar. 31, 2019
Short Term Investments [Abstract] |
Short-term investments, contractual maturity period | 2020-02

X
- Definition Investment maturity month and year range start. + References No definition available. + Details
Name: | geos_InvestmentMaturityMonthAndYearRangeStart
Namespace Prefix: | geos_
Data Type: | xbrli:gYearMonthItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_ShortTermInvestmentsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration