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Revenue From Contracts With Customers - Backlog By Segment (Details) - USD ($)
$ in Thousands
Jun. 30, 2020
Dec. 31, 2019
Disaggregation of Revenue [Line Items]    
Backlog $ 1,133,814 $ 1,068,025
Heavy Civil    
Disaggregation of Revenue [Line Items]    
Backlog 874,822 834,049
Specialty Services    
Disaggregation of Revenue [Line Items]    
Backlog $ 258,992 $ 233,976