Goodwill and Intangible Assets (Changes in Carrying Amount of Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Line Items]
Gross goodwill as of December 31, 2019			$ 1,072,991
Accumulated impairment as of December 31, 2019	$ (867,800)		(867,848)
Balance at beginning of period	205,143	$ 205,143
Activity	0	0
Balance at end of period	205,143	205,143
Civil
Goodwill [Line Items]
Gross goodwill as of December 31, 2019			492,074
Accumulated impairment as of December 31, 2019			(286,931)
Balance at beginning of period	205,143	205,143
Activity	0	0
Balance at end of period	205,143	205,143
Building
Goodwill [Line Items]
Gross goodwill as of December 31, 2019			424,724
Accumulated impairment as of December 31, 2019			(424,724)
Balance at beginning of period	0	0
Activity	0	0
Balance at end of period	0	0
Specialty Contractors
Goodwill [Line Items]
Gross goodwill as of December 31, 2019			156,193
Accumulated impairment as of December 31, 2019			$ (156,193)
Balance at beginning of period	0	0
Activity	0	0
Balance at end of period	$ 0	$ 0