Business Combinations (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pro forma results
Percentage of pro forma tax rate used in calculating taxes on income from continuing operations	39.00%	39.00%	39.00%	39.00%
Revenues	$ 517,276	$ 446,817	$ 988,955	$ 860,893
Income before provision for income taxes	26,804	25,122	44,726	39,633
Net income attributable to Primoris	$ 16,115	$ 15,100	$ 26,684	$ 23,810
Weighted average common shares outstanding:
Basic (in shares)	51,655	51,562	51,631	51,510
Diluted (in shares)	51,804	51,626	51,759	51,547
Earnings per share:
Basic (in dollars per share)	$ 0.31	$ 0.29	$ 0.52	$ 0.46
Diluted (in dollars per share)	$ 0.31	$ 0.29	$ 0.52	$ 0.46

Name:	prim_BusinessAcquisitionProFormaEarningsPerShareAbstract
Namespace Prefix:	prim_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the 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

Name:	prim_BusinessAcquisitionProFormaTaxRateUsedInCalculatingTaxesOnIncomeFromContinuingOperations
Namespace Prefix:	prim_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- 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

Name:	prim_BusinessAcquisitionProFormaWeightedAverageNumberOfDilutedSharesOutstanding
Namespace Prefix:	prim_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	prim_BusinessAcquisitionProFormaWeightedAverageNumberOfSharesOutstandingAbstract
Namespace Prefix:	prim_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

Name:	prim_BusinessAcquisitionProFormaWeightedAverageNumberOfSharesOutstandingBasic
Namespace Prefix:	prim_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	prim_BusinessAcquisitionsProFormaIncomeLossFromContinuingOperationsBeforeIncomeTaxes
Namespace Prefix:	prim_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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=25497992&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- 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

Name:	us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionProFormaInformationAbstract
Namespace Prefix:	us-gaap_
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

Name:	us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss
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

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