Business Segments (Reconciliation of Segment Results to Consolidated Income Before Income Taxes) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Total assets	$ 4,429,856	$ 4,542,800
Corporate, Non-Segment
Total assets	(315,825)	(242,485)
Civil | Operating Segments
Total assets	3,539,608	3,402,934
Building | Operating Segments
Total assets	898,902	898,816
Specialty Contractors | Operating Segments
Total assets	$ 307,171	$ 483,535