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Reportable Segments - Revenue and Total Assets by Geographic Area (Details) | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Revenues and total assets by geographic area |  |  |
% of Revenue | 100.00% | 100.00% | 100.00%
Non-United States |  |  |
Revenues and total assets by geographic area |  |  |
% of Revenue | 2.90% | 0.30% | 0.60%
% of total assets | 2.80% | 1.00% |

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- Definition The percentage of revenue to total revenue. + References No definition available. + Details
Name: | prim_RevenuePercentage
Namespace Prefix: | prim_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition The percentage of assets to total assets. + References No definition available. + Details
Name: | prim_TotalAssetsPercentage
Namespace Prefix: | prim_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- 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
Name: | us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_StatementGeographicalAxis=prim_NonUnitedStatesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |