Business Segments (Total Assets For Reportable Segments) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Total assets	$ 4,468,515	$ 4,542,800
Corporate and other
Segment Reporting Information [Line Items]
Total assets	(258,381)	(242,485)
Civil | Operating Segments
Segment Reporting Information [Line Items]
Total assets	3,459,839	3,402,934
Building | Operating Segments
Segment Reporting Information [Line Items]
Total assets	909,226	898,816
Specialty Contractors | Operating Segments
Segment Reporting Information [Line Items]
Total assets	$ 357,831	$ 483,535