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Property and Equipment - Summary (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 152,161 $ 153,015
Less accumulated depreciation (100,019) (98,609)
Total property and equipment, net 52,142 54,406
Construction equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 119,011 118,868
Transportation equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 17,347 17,511
Buildings    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 9,577 9,577
Office equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 2,706 3,339
Leasehold improvement    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 914 914
Construction in progress    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 258 258
Land    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 2,348 2,348
Water rights    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 0 $ 200