Document and Entity Information Statement [Table] Statement [Line Items] Statement Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Current Reporting Status Entity Filer Category Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Period Focus Entity Small Business Entity Emerging Growth Company CONDENSED CONSOLIDATED BALANCE SHEETS Assets [Abstract] ASSETS Assets, Current [Abstract] Current assets: Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents ($15,729 and $ 60,256 related to VIEs. See Note 11) Cash and cash equivalents Receivables, Net, Current Accounts receivable, net Accounts receivable Contract with Customer, Asset, Net, Current Contract assets Contract assets Prepaid Expense and Other Assets, Current Prepaid expenses and other current assets Assets, Current Total current assets Property, Plant and Equipment, Net Property and equipment, net Deferred Income Tax Assets, Net Deferred tax assets Intangible Assets, Net (Excluding Goodwill) Intangible assets, net Total Goodwill Goodwill, Ending Balance Goodwill, Beginning Balance Goodwill Other Assets, Noncurrent Other long-term assets Assets Total assets Liabilities and Equity [Abstract] LIABILITIES AND STOCKHOLDERS’ EQUITY Liabilities, Current [Abstract] Current liabilities: Accounts Payable, Current Accounts payable Contract with Customer, Liability, Current Contract liabilities Contract liabilities Accrued Liabilities, Current Accrued liabilities Total accrued expenses and other current liabilities Dividends Payable, Current Dividends payable Long-term Debt, Current Maturities Less: current portion Current portion of long-term debt Liabilities, Current Total current liabilities Long-term Debt, Excluding Current Maturities Long-term debt, net of current portion Deferred Tax Liabilities, Net, Noncurrent Deferred tax liabilities Other Liabilities, Noncurrent Other long-term liabilities Liabilities Total liabilities Total liabilities Commitments and Contingencies Commitments and contingencies (See Note 17) Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Stockholders' equity Common Stock, Value, Issued Common stock—$.0001 par value; 90,000,000 shares authorized; 51,204,959 and 51,448,753 issued and outstanding at September 30, 2018 and December 31, 2017 Additional Paid in Capital, Common Stock Additional paid-in capital Retained Earnings (Accumulated Deficit) Retained earnings Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive income Stockholders' Equity Attributable to Noncontrolling Interest Noncontrolling interest Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total stockholders’ equity Liabilities and Equity Total liabilities and stockholders’ equity Schedule of Variable Interest Entities [Table] Variable Interest Entity [Line Items] VIEs Common Stock, Par or Stated Value Per Share Common stock, par value (in dollars per share) Common Stock, Shares Authorized Common stock, shares authorized Common Stock, Shares, Issued Common stock, shares issued Common Stock, Shares, Outstanding Common stock, shares outstanding CONDENSED CONSOLIDATED STATEMENTS OF INCOME Revenues Revenue Cost of Services, Excluding Depreciation, Depletion, and Amortization Cost of revenue Gross Profit Gross Profit Gross profit Gross profit Selling, General and Administrative Expense Selling, general and administrative expenses Business Combination, Acquisition Related Costs Acquisition and related costs Operating Income (Loss) Operating income Nonoperating Income (Expense) [Abstract] Other income (expense): Marketable Securities, Unrealized Gain (Loss) Investment income Foreign Currency Transaction Gain (Loss), before Tax Foreign exchange gain Other Nonoperating Income (Expense) Other income (expense), net Contingent consideration credited to non-operating income Investment Income, Interest Interest income Interest Expense Interest expense Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Income before provision for income taxes Income Tax Expense (Benefit) Provision for income taxes Tax effect on income recognized Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income Net income Net Income (Loss) Attributable to Noncontrolling Interest Less net income attributable to noncontrolling interests Net income attributable to noncontrolling interests Net Income (Loss) Available to Common Stockholders, Basic Net income attributable to Primoris Net income attributable to Primoris Common Stock, Dividends, Per Share, Declared Dividends per common share (in dollars per share) Cash dividend declared (in dollars per share) Earnings Per Share Earnings per share: Earnings Per Share, Basic Basic (in dollars per share) Basic earnings per share (in dollars per share) Earnings Per Share, Diluted Diluted (in dollars per share) Diluted earnings per share (in dollars per share) Weighted Average Number of Shares Outstanding, Diluted [Abstract] Weighted average common shares outstanding: Denominator: Weighted Average Number of Shares Outstanding, Basic Basic (in shares) Weighted average shares for computation of basic earnings per share Weighted Average Number of Shares Outstanding, Diluted Diluted (in shares) Weighted average shares for computation of diluted earnings per share CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Other comprehensive income, net of tax: Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Foreign currency translation adjustments Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive income attributable to Primoris CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Cash flows from operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash (used in) provided by operating activities (net of effect of acquisitions): Depreciation Depreciation Amortization of Intangible Assets Amortization expense of intangible assets Amortization of intangible assets Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill) Intangible asset impairment Share-based Compensation Stock-based compensation expense Gain on Sale of Investments Gain on short-term investments Gain (Loss) on Disposition of Property Plant Equipment Gain on sale of property and equipment Other Noncash Expense Other non-cash items Increase (Decrease) in Operating Capital [Abstract] Changes in assets and liabilities: Increase (Decrease) in Receivables Accounts receivable Increase (Decrease) in Contract with Customer, Asset Contract assets Increase (Decrease) in Other Current Assets Other current assets Increase (Decrease) in Other Noncurrent Assets Other long-term assets Increase (Decrease) in Accounts Payable Accounts payable Increase (Decrease) in Contract with Customer, Liability Contract liabilities Increase (Decrease) in Accrued Liabilities Accrued liabilities Increase (Decrease) in Other Noncurrent Liabilities Other long-term liabilities Net Cash Provided by (Used in) Operating Activities, Continuing Operations Net cash (used in) provided by operating activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Cash flows from investing activities: Payments to Acquire Property, Plant, and Equipment Purchase of property and equipment Payments to Acquire Notes Receivable Issuance of a note receivable Proceeds from Sale of Notes Receivable Proceeds from a note receivable Proceeds from Sale of Property, Plant, and Equipment Proceeds from sale of property and equipment Payments to Acquire Short-term Investments Purchase of short-term investments Proceeds from Sale of Short-term Investments Sale of short-term investments Payments to Acquire Businesses, Net of Cash Acquired Cash paid for acquisitions, net of cash and restricted cash acquired Purchase consideration, net of cash acquired Net cash paid Net Cash Provided by (Used in) Investing Activities, Continuing Operations Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Cash flows from financing activities: Proceeds from Lines of Credit Borrowings under revolving line of credit Repayments of Lines of Credit Payments on revolving line of credit Proceeds from Issuance of Long-term Debt Proceeds from issuance of long-term debt Payments to Noncontrolling Interests Cash distribution to non-controlling interest holder Payment for Contingent Consideration Liability, Financing Activities Payment of contingent earnout liability Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities Repayment of long-term debt and capital leases Payments of Debt Issuance Costs Payment of debt issuance cost Proceeds from Issuance of Common Stock Proceeds from issuance of common stock purchased under a long-term incentive plan Payments for Repurchase of Common Stock Repurchase of common stock Payments of Ordinary Dividends, Common Stock Dividends paid Net Cash Provided by (Used in) Financing Activities, Continuing Operations Net cash provided by (used in) financing activities Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Effect of exchange rate changes on cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Net change in cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash and cash equivalents at end of the period Cash and cash equivalents at beginning of the period Cash, cash equivalents and restricted cash Supplemental Cash Flow Information [Abstract] SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION Cash Paid During Year [Abstract] Cash paid: Interest Paid Interest Income Taxes Paid Income taxes, net of refunds received Noncash Investing and Financing Items [Abstract] SUPPLEMENTAL DISCLOSURES OF NONCASH INVESTING AND FINANCING ACTIVITIES Capital Expenditures Incurred but Not yet Paid Obligations incurred for the acquisition of property Dividends Payable Dividends declared and not yet paid Nature of Business Nature of Operations [Text Block] Nature of Business Basis of Presentation Basis of Presentation and Significant Accounting Policies [Text Block] Basis of Presentation Recent Accounting Pronouncements New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Recent Accounting Pronouncements Revenue Revenue from Contract with Customer [Text Block] Revenue Fair Value Measurements Fair Value Disclosures [Text Block] Fair Value Measurements Business Combinations Business Combination Disclosure [Text Block] Business Combinations Goodwill and Intangible Assets Goodwill and Intangible Assets Disclosure [Text Block] Goodwill and Intangible Assets Accounts Payable and Accrued Liabilities Accounts Payable and Accrued Liabilities Disclosure [Text Block] Accounts Payable and Accrued Liabilities Credit Arrangements Debt Disclosure [Text Block] Credit Arrangements Derivative Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Derivative Instruments Noncontrolling Interests Noncontrolling Interest Disclosure [Text Block] Noncontrolling Interests Related Party Transactions Related Party Transactions Disclosure [Text Block] Related Party Transactions Stock-Based Compensation. Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Stock-Based Compensation Income Taxes Income Tax Disclosure [Text Block] Income Taxes No definition available. Dividends and Earnings Per Share The entire disclosure for dividends paid or declared and earnings per share. Dividends and Earnings Per Share Disclosure [Text Block] Dividends and Earnings Per Share Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Stockholders' Equity Commitments and Contingencies. Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Reportable Segments Segment Reporting Disclosure [Text Block] Reportable Segments Subsequent Events. Subsequent Events [Text Block] Subsequent Events Reclassification, Policy [Policy Text Block] Reclassification Concentration Risk, Credit Risk, Policy [Policy Text Block] Customer concentration Pension and Other Postretirement Plans, Policy [Policy Text Block] Multiemployer plans Revenue Recognition, Policy [Policy Text Block] Revenue recognition Derivatives, Policy [Policy Text Block] Derivative instruments and hedging activities Tabular disclosure of contract assets balances and changes in contract assets balances. Contract with Customer, Asset [Table Text Block] Schedule of contract assets Tabular disclosure of contract liabilities balances and changes in contract liabilities balances. Contract with Customer, Liability [Table Text Block] Schedule of contract liabilities Disaggregation of Revenue [Table Text Block] Schedule of revenue disaggregation by various categories Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of financial assets and liabilities which are required to be measured at fair value Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Schedule of changes to the Company's contingent consideration liability Level 3 fair value measurements Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Line Items] Business combinations Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Summary of the fair value of assets acquired and the liabilities assumed Business Acquisition, Pro Forma Information [Table Text Block] Schedule of pro forma results Tabular presentation of goodwill by reporting unit. Schedule of Goodwill by Reporting Unit [Table Text Block] Schedule of goodwill by reporting unit Schedule of Finite-Lived Intangible Assets [Table Text Block] Summary of intangible asset categories, amounts and the average amortization periods Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Schedule of estimated future amortization expense for intangible assets Schedule of Accrued Liabilities [Table Text Block] Summary of accrued expenses and other current liabilities Schedule of Long-term Debt Instruments [Table Text Block] Schedule of long-term debt and credit facilities Schedule of Derivative Assets at Fair Value [Table Text Block] Schedule of fair values of our derivative contracts included in the Condensed Consolidated Balance Sheets Derivative Instruments, Gain (Loss) [Table Text Block] Schedule of derivative instruments within the Condensed Consolidated Statements of Income Tabular disclosure of operating activities of the variable interest entity (VIE) included in the entity's consolidated income statement. Schedule of Operating Activities of Variable Interest Entities Included in Consolidated Income Statement [Table Text Block] Schedule of joint venture operating activities included in the Company's consolidated statements of income