Business Segments (Principal Geographical Areas) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Principal Geographical Areas Information
Revenue from external customers	$ 3,880,227	$ 3,790,755	$ 4,641,830
Total assets	4,429,856	4,542,800
Civil
Principal Geographical Areas Information
Revenue from external customers	$ 1,883,865	$ 1,734,882	2,095,760
Civil, Building, and Specialty Contractors | Customer Concentration Risk | Revenue Benchmark
Principal Geographical Areas Information
Concentration risk, percentage	16.30%	16.30%
United States
Principal Geographical Areas Information
Revenue from external customers	$ 3,437,971	$ 3,424,574	4,267,734
Total assets	3,998,470	4,199,604
Foreign and U.S. territories
Principal Geographical Areas Information
Revenue from external customers	442,256	366,181	$ 374,096
Total assets	$ 431,386	$ 343,196