Term of the interest rate that fluctuates over time as a result of an underlying benchmark interest rate or index.

No definition available.

Name:	gvp_DebtInstrumentTermOfVariableRate
Namespace Prefix:	gvp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Refers to the fixed charge coverage ratio.

+ References

No definition available.

+ Details

Name:	gvp_FixedChargeCoverageRatio
Namespace Prefix:	gvp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Refers to the leverage ratio.

+ References

No definition available.

+ Details

Name:	gvp_LeverageRatio
Namespace Prefix:	gvp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This item represents the number of letters of credit on which the entity is contingently liable.

+ References

No definition available.

+ Details

Name:	gvp_NumberOfLettersOfCredit
Namespace Prefix:	gvp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Refers to the percentage of letter of credit fees per annum.

+ References

No definition available.

+ Details

Name:	gvp_PercentageOfLetterOfCreditFeesPerAnnum
Namespace Prefix:	gvp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	gvp_TermLoanAbstract
Namespace Prefix:	gvp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For indemnification assets recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the indemnification benefit which may be realized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=116869197&loc=d3e4845-128472

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of the amount outstanding under the credit facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

Expenses paid for obtaining loans which includes expenses such as application and origination fees.

+ References

No definition available.

+ Details

Name:	us-gaap_LoanProcessingFee
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of loans from a bank with maturities initially due after one year or beyond the normal operating cycle if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Carrying value as of the balance sheet date of current portion of long-term loans payable to bank due within one year or the operating cycle if longer.

+ References

+ Details

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

- Definition

Carrying value as of the balance sheet date of loans from a bank with maturities initially due after one year or beyond the operating cycle if longer, excluding current portion.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(2))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

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

- References

No definition available.

+ Details

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

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

+ Details

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

- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

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

- Details

Name:	srt_StatementScenarioAxis=us-gaap_ScenarioPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=gvp_CitizenSBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gvp_DelayedDrawTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=gvp_DPEngineeringLtdCoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=gvp_TrueNorthConsultingLLCMember
Namespace Prefix:
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Period Type:

Debt (Details) $ in Thousands			6 Months Ended
Debt (Details) $ in Thousands	Feb. 15, 2019 USD ($)	May 11, 2018 USD ($)	Jun. 30, 2019 USD ($) Letter	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 28, 2019	Dec. 31, 2018 USD ($)	Dec. 29, 2016 USD ($)
Line of Credit Facility [Abstract]
Leverage ratio			275.00%
Number of letters of credit \| Letter			3
Plan [Member]
Line of Credit Facility [Abstract]
Leverage ratio				225.00%	225.00%	225.00%	225.00%	250.00%	250.00%	275.00%	275.00%	275.00%
LIBOR [Member]
Term Loan [Abstract]
Term of variable rate			1 month
Minimum [Member]
Line of Credit Facility [Abstract]
Fixed charge coverage ratio													105.00%
Maximum [Member]
Line of Credit Facility [Abstract]
Fixed charge coverage ratio													125.00%
Citizen's Bank [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility [Abstract]
Line of credit facility expiration period			3 years
Principal amount of the line of credit															$ 5,000
Line of credit facility term			5 years
Outstanding letter of credit balance			$ 0
Number of letters of credit \| Letter			3
Outstanding letter of credit balance			$ 900
Line of credit facility, remaining borrowing capacity			$ 4,100
Citizen's Bank [Member] \| Revolving Credit Facility [Member] \| Minimum [Member]
Line of Credit Facility [Abstract]
Percentage of letter of credit fees per annum			1.25%
Citizen's Bank [Member] \| Revolving Credit Facility [Member] \| Maximum [Member]
Line of Credit Facility [Abstract]
Percentage of letter of credit fees per annum			2.00%
Delayed Draw Term Loan [Member]
Long-term Debt, Current and Noncurrent [Abstract]
Long-term debt, net of discount			$ 20,934											$ 8,512
Less: current portion of long-term debt			(4,773)											(1,902)
Long-term debt, less current portion			$ 16,161											$ 6,610
Delayed Draw Term Loan [Member] \| Minimum [Member]
Term Loan [Abstract]
Debt instrument, basis spread on variable rate			2.00%
Delayed Draw Term Loan [Member] \| Maximum [Member]
Term Loan [Abstract]
Debt instrument, basis spread on variable rate			2.75%
Delayed Draw Term Loan [Member] \| Citizen's Bank [Member] \| Maximum [Member]
Line of Credit Facility [Abstract]
Line of credit facility expiration period			18 months
Delayed Draw Term Loan [Member] \| Citizen's Bank [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility [Abstract]
Principal amount of the line of credit		$ 25,000
DP Engineering Ltd, CO. [Member]
Term Loan [Abstract]
Cash purchase price	$ 13,500
Proceeds from issuance of debt	14,263
Earn-out amount	$ 5,000
DP Engineering Ltd, CO. [Member] \| Delayed Draw Term Loan [Member]
Line of Credit Facility [Abstract]
Line of credit facility term	5 years
DP Engineering Ltd, CO. [Member] \| Delayed Draw Term Loan [Member] \| LIBOR [Member]
Term Loan [Abstract]
Term of variable rate			1 month
DP Engineering Ltd, CO. [Member] \| Delayed Draw Term Loan [Member] \| Minimum [Member]
Term Loan [Abstract]
Debt instrument, basis spread on variable rate	2.00%
DP Engineering Ltd, CO. [Member] \| Delayed Draw Term Loan [Member] \| Maximum [Member]
Term Loan [Abstract]
Debt instrument, basis spread on variable rate	2.75%
True North Consulting, LLC [Member]
Term Loan [Abstract]
Cash purchase price		9,750
Proceeds from issuance of debt		10,300
True North Consulting, LLC [Member] \| Delayed Draw Term Loan [Member]
Line of Credit Facility [Abstract]
Line of credit facility term			5 years
Term Loan [Abstract]
Proceeds from issuance of debt		10,300
Repayments of debt		$ 500
Debt issuance costs			$ 70
Loan origination fees			$ 75
True North Consulting, LLC [Member] \| Delayed Draw Term Loan [Member] \| LIBOR [Member]
Term Loan [Abstract]
Term of variable rate			1 month
True North Consulting, LLC [Member] \| Delayed Draw Term Loan [Member] \| Citizen's Bank [Member] \| Minimum [Member]
Term Loan [Abstract]
Debt instrument, basis spread on variable rate			2.00%
True North Consulting, LLC [Member] \| Delayed Draw Term Loan [Member] \| Citizen's Bank [Member] \| Maximum [Member]
Term Loan [Abstract]
Debt instrument, basis spread on variable rate			2.75%