Business Segments (Reconciliation of Segment Results to Consolidated Income Before Income Taxes) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets	$ 4,724,898	$ 5,045,617
Corporate, Non-Segment
Assets	(198,449)	82,086
Civil | Operating Segments
Assets	3,310,648	3,141,991
Building | Operating Segments
Assets	980,989	1,147,649
Specialty Contractors | Operating Segments
Assets	$ 631,710	$ 673,891