Business Segments (Total Assets For Reportable Segments) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Total assets	$ 4,476,778	$ 4,542,800
Corporate and other
Segment Reporting Information [Line Items]
Total assets	(157,092)	(242,485)
Civil | Operating Segments
Segment Reporting Information [Line Items]
Total assets	3,368,743	3,402,934
Building | Operating Segments
Segment Reporting Information [Line Items]
Total assets	879,321	898,816
Specialty Contractors | Operating Segments
Segment Reporting Information [Line Items]
Total assets	$ 385,806	$ 483,535