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Construction Joint Ventures - Narrative (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Nov. 27, 2015
Schedule of Equity Method Investments [Line Items]      
Noncontrolling interests $ 4,856 $ 656  
Joint Ventures      
Schedule of Equity Method Investments [Line Items]      
Sterling’s noncontrolling interest in backlog $ 55,096 $ 52,992  
Granite Construction Corporation      
Schedule of Equity Method Investments [Line Items]      
Equity Method Investment, Ownership Percentage 50.00%    
Myers      
Schedule of Equity Method Investments [Line Items]      
Noncontrolling interests     $ 7,400