Revenue From Contracts With Customers - By Major Market End (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total Revenue	$ 291,699	$ 291,266	$ 779,734	$ 782,492
Heavy Civil Construction
Disaggregation of Revenue [Line Items]
Total Revenue	251,757	254,544	661,071	665,068
Heavy Civil Construction \| Heavy Highway
Disaggregation of Revenue [Line Items]
Total Revenue	142,118	151,882	365,692	385,844
Heavy Civil Construction \| Commercial
Disaggregation of Revenue [Line Items]
Total Revenue	34,875	32,261	94,300	89,889
Heavy Civil Construction \| Aviation
Disaggregation of Revenue [Line Items]
Total Revenue	39,105	30,587	106,103	81,671
Heavy Civil Construction \| Water Containment and Treatment
Disaggregation of Revenue [Line Items]
Total Revenue	15,960	18,457	46,709	48,973
Heavy Civil Construction \| Other Revenue
Disaggregation of Revenue [Line Items]
Total Revenue	$ 19,699	$ 21,357	$ 48,267	$ 58,691