Business Segments (Total Assets for Reportable Segments) (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Total assets	$ 4,293,748	$ 4,429,856
Corporate and other
Segment Reporting Information [Line Items]
Total assets	(501,447)	(315,825)
Civil | Operating Segments
Segment Reporting Information [Line Items]
Total assets	3,520,109	3,539,608
Building | Operating Segments
Segment Reporting Information [Line Items]
Total assets	1,028,958	898,902
Specialty Contractors | Operating Segments
Segment Reporting Information [Line Items]
Total assets	$ 246,128	$ 307,171