Revenue From Contracts With Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 296,688	$ 223,949
Fixed-Unit Price
Disaggregation of Revenue [Line Items]
Revenues	141,739	141,219
Lump Sum
Disaggregation of Revenue [Line Items]
Revenues	114,252	39,132
Residential and Other
Disaggregation of Revenue [Line Items]
Revenues	40,697	43,598
Heavy Civil
Disaggregation of Revenue [Line Items]
Revenues	155,615	150,505
Heavy Civil | Heavy Highway
Disaggregation of Revenue [Line Items]
Revenues	96,374	93,610
Heavy Civil | Aviation
Disaggregation of Revenue [Line Items]
Revenues	28,457	29,937
Heavy Civil | Water Containment and Treatment
Disaggregation of Revenue [Line Items]
Revenues	21,809	15,234
Heavy Civil | Other
Disaggregation of Revenue [Line Items]
Revenues	8,975	11,724
Specialty Services
Disaggregation of Revenue [Line Items]
Revenues	104,723	30,679
Specialty Services | Land Development
Disaggregation of Revenue [Line Items]
Revenues	76,245	0
Specialty Services | Commercial
Disaggregation of Revenue [Line Items]
Revenues	28,478	30,679
Specialty Services
Disaggregation of Revenue [Line Items]
Revenues	$ 36,350	$ 42,765