Business acquisition contingent consideration included in accounts payable.

No definition available.

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Namespace Prefix:	gpx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Business acquisition contingent consideration included in other long term liability.

+ References

No definition available.

+ Details

Name:	gpx_BusinessAcquisitionContingentConsiderationOtherLongTermLiability
Namespace Prefix:	gpx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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Acquisitions - Narrative (Details) - USD ($) $ in Thousands	Jan. 02, 2018	Mar. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Business combination, contingent consideration arrangements, range of outcomes, value, high		$ 16,214
Business acquisition, contingent consideration accounts payable		1,400	$ 2,700
Business acquisition, contingent consideration other long term liability		300	1,500
Goodwill		154,590	$ 144,835
Hula Partners [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 10,000
Goodwill	8,527
CLS
Business Acquisition [Line Items]
Business combination, contingent consideration arrangements, range of outcomes, value, high		2,312
McKinney Rogers
Business Acquisition [Line Items]
Business combination, contingent consideration arrangements, range of outcomes, value, high		$ 8,000
Customer relationships \| Hula Partners [Member]
Business Acquisition [Line Items]
Intangible assets, other than goodwill	$ 1,367