Fair Value of Financial Instruments (Details) (USD $)	Dec. 31, 2014 Contract Bond Letter	Dec. 31, 2013
Performance Bond Abstract
Number of Standby Letters of Credit	12gvp_NumberOfStandbyLettersOfCredit
Number of Surety Bonds	1gvp_NumberOfSuretyBonds
Letter of Credit and Surety Bonds	$ 4,200,000
Number of Performance and Bid Bonds issued in relation to contracts	11gvp_NumberOfBidBondsContract
Number of stand by letters of credit deposited in escrow accounts	11
Restricted cash and investments	4,200,000	1,100,000
Unrestricted cash	7,500,000us-gaap_Cash	9,500,000us-gaap_Cash
Assets and liabilities measured at fair value [Abstract]
Money market funds	11,661,000	10,553,000
Foreign exchange contracts - Assets	92,000	142,000
Total assets	11,753,000us-gaap_AssetsFairValueDisclosure	10,695,000us-gaap_AssetsFairValueDisclosure
Foreign exchange contracts - Liabilities	24,000	655,000
Total liabilities	24,000us-gaap_LiabilitiesFairValueDisclosure	655,000us-gaap_LiabilitiesFairValueDisclosure
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets and liabilities measured at fair value [Abstract]
Money market funds	11,661,000	10,553,000
Foreign exchange contracts - Assets	0	0
Total assets	11,661,000	10,553,000
Foreign exchange contracts - Liabilities	0	0
Total liabilities	0	0
Significant Other Observable Inputs (Level 2) [Member]
Assets and liabilities measured at fair value [Abstract]
Money market funds	0	0
Foreign exchange contracts - Assets	92,000	142,000
Total assets	92,000	142,000
Foreign exchange contracts - Liabilities	24,000	655,000
Total liabilities	24,000	655,000
Significant Unobservable Inputs (Level 3) [Member]
Assets and liabilities measured at fair value [Abstract]
Money market funds	0	0
Foreign exchange contracts - Assets	0	0
Total assets	0	0
Foreign exchange contracts - Liabilities	0	0
Total liabilities	$ 0	$ 0

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This item represents the amount of standby letters of credit and surety bonds for which the entity is contingently liable.

+ References

No definition available.

+ Details

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- Definition

This item represents the number of bid bonds contract.

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

Number of stand by letters of credit deposited in escrow accounts

+ References

No definition available.

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- Definition

This item represents the number of surety bonds on which the entity is contingently liable.

+ References

No definition available.

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

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- Definition

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

-URI http://asc.fasb.org/extlink&oid=6506951

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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-Name Accounting Standards Codification

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

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- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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- Definition

Fair value portion of asset contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward contracts, and swaps.

+ References

No definition available.

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- Definition

Fair value portion of liability contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward (delivery or nondelivery) contracts, and swaps entered into.

+ References

No definition available.

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- Definition

Fair value of financial and nonfinancial obligations.

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- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

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