Revenue From Contracts With Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 400,038	$ 264,086	$ 696,726	$ 488,035
Fixed-Unit Price
Disaggregation of Revenue [Line Items]
Revenues	203,692	185,297	345,431	326,516
Lump Sum
Disaggregation of Revenue [Line Items]
Revenues	147,460	43,666	261,712	82,798
Residential and Other
Disaggregation of Revenue [Line Items]
Revenues	48,886	35,123	89,583	78,721
Heavy Civil
Disaggregation of Revenue [Line Items]
Revenues	220,448	200,236	376,063	350,741
Heavy Civil | Heavy Highway
Disaggregation of Revenue [Line Items]
Revenues	152,526	129,964	248,900	223,574
Heavy Civil | Aviation
Disaggregation of Revenue [Line Items]
Revenues	34,867	37,061	63,324	66,998
Heavy Civil | Water Containment and Treatment
Disaggregation of Revenue [Line Items]
Revenues	16,529	15,515	38,338	30,749
Heavy Civil | Other
Disaggregation of Revenue [Line Items]
Revenues	16,526	17,696	25,501	29,420
Specialty Services
Disaggregation of Revenue [Line Items]
Revenues	135,703	27,894	240,426	58,573
Specialty Services | Land Development
Disaggregation of Revenue [Line Items]
Revenues	105,639	0	181,884	0
Specialty Services | Commercial
Disaggregation of Revenue [Line Items]
Revenues	30,064	27,894	58,542	58,573
Residential
Disaggregation of Revenue [Line Items]
Revenues	$ 43,887	$ 35,956	$ 80,237	$ 78,721