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Reportable Operating Segments (Details 2)
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Revenues and total assets by geographic area    
% of Revenue 100.00%prim_RevenuePercentage 100.00%prim_RevenuePercentage
Non-United States    
Revenues and total assets by geographic area    
% of total assets 1.00%prim_TotalAssetsPercentage
/ us-gaap_StatementGeographicalAxis
= prim_NonUnitedStatesMember		  
Non-United States | Maximum    
Revenues and total assets by geographic area    
% of Revenue 1.00%prim_RevenuePercentage
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_StatementGeographicalAxis
= prim_NonUnitedStatesMember