Business Segments (Total Assets for Reportable Segments) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Total assets	$ 4,370,407	$ 4,429,856
Corporate and other
Segment Reporting Information [Line Items]
Total assets	(282,813)	(315,825)
Civil | Operating Segments
Segment Reporting Information [Line Items]
Total assets	3,426,013	3,539,608
Building | Operating Segments
Segment Reporting Information [Line Items]
Total assets	957,202	898,902
Specialty Contractors | Operating Segments
Segment Reporting Information [Line Items]
Total assets	$ 270,005	$ 307,171