Name:	prim_BusinessAcquisitionProFormaEarningsPerShareAbstract
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Represents the percentage of pro forma tax rate used in calculating taxes on income from continuing operations for a period, as if the business combination or combinations had been completed at the beginning of a period.

+ References

No definition available.

+ Details

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- Definition

The pro forma number of diluted weighted average shares outstanding for a period, as if the business combination or combinations had been completed at the beginning of a period.

+ References

No definition available.

+ Details

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- Definition

The pro forma number of basic weighted average shares outstanding for a period, as if the business combination or combinations had been completed at the beginning of a period.

+ References

No definition available.

+ Details

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- Definition

The pro forma income from continuing operations before tax effect for the period, as if the business combination or combinations had been completed at the beginning of a period.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Number of shares of equity interests issued or issuable to acquire entity.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(2)-(3)

-URI http://asc.fasb.org/extlink&oid=7659399&loc=d3e1392-128463

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 54

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 55

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 68

-Subparagraph r(2, 3)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic
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Data Type:	num:perShareItemType
Balance Type:	na
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- Definition

The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

+ Details

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- Details

Name:	us-gaap_BusinessAcquisitionProFormaInformationAbstract
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

+ Details

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

- Definition

The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

+ References

+ Details

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Business Combinations (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		0 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 12, 2012 Sprint	Mar. 31, 2013 Sprint	Jan. 31, 2013 Q3 Contracting	Mar. 31, 2013 Q3 Contracting
Pro forma results
Percentage of pro forma tax rate used in calculating taxes on income from continuing operations				39.00%
Unregistered shares of common stock issued with an acquisition			62,052	62,052	29,273	29,273
Revenues	$ 412,794	$ 318,415
Income before provision for income taxes	16,162	14,241
Net income attributable to Primoris	$ 9,718	$ 8,746
Weighted average common shares outstanding:
Basic (in shares)	51,456,000	51,145,000
Diluted (in shares)	51,467,000	51,386,000
Earnings per share attributable to Primoris:
Basic (in dollars per share)	$ 0.19	$ 0.17
Diluted (in dollars per share)	$ 0.19	$ 0.17