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Summary of Significant Accounting Policies (Details 4) | 1 Months Ended | 12 Months Ended
--- | --- | ---
Aug. 31, 2012 | Mar. 31, 2012 | Feb. 29, 2012 | Aug. 31, 2011 | Mar. 31, 2011 | Dec. 31, 2012 | Dec. 31, 2011
Share-based payments and stock-based compensation |  |  |  |  |  |  |
Shares of common stock reserved for issuance upon exercise of all future stock option grants, SARS and grants of restricted shares under the 2008 Equity Plan |  |  |  |  |  | 1,270,744 |
Issuance of employee LTI shares (in shares) |  | 111,790 |  |  | 94,966 | 111,790 | 94,966
Period of restriction on trade for shares issued to employees under the Primoris Long-term Retention Plan |  |  |  |  |  | 6 months |
Shares of common stock issued as a part of quarterly compensation of non-employee members of the Board of Directors | 15,280 |  | 12,395 | 14,825 |  | 27,675 | 14,825
Period of restriction on trade for shares issued to non-employee members of the board of directors under the Primoris Long-term Retention Plan |  |  |  |  |  | 1 year |
Minimum |  |  |  |  |  |  |
Property and equipment |  |  |  |  |  |  |
Estimated useful lives of the related assets |  |  |  |  |  | 3 years |
Maximum |  |  |  |  |  |  |
Property and equipment |  |  |  |  |  |  |
Estimated useful lives of the related assets |  |  |  |  |  | 30 years |

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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of shares issued during the period as a result of an employee stock purchase plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187085-122770 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 5 -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 AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 -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 SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30 -Article 5 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 + Details
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