Business Segments (Reportable Segments) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Revenue	$ 776,300	$ 952,154
Income (loss) from construction operations	(81,945)	(9,907)
Capital expenditures	17,796	12,028
Depreciation and amortization	10,408	20,238
Adverse Legal Ruling Pertaining to Transit Project in New York
Segment Reporting Information [Line Items]
Loss contingency	83,600
Loss contingency, after tax	$ 60,100
Loss contingency, after tax, diluted (in dollars per share)	$ 1.17
Operating Segments
Segment Reporting Information [Line Items]
Revenue	$ 804,263	1,047,584
Income (loss) from construction operations	(64,645)	4,603
Capital expenditures	17,526	11,815
Depreciation and amortization	8,057	17,903
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(27,963)	(95,430)
Corporate
Segment Reporting Information [Line Items]
Revenue	0	0
Income (loss) from construction operations	(17,300)	(14,510)
Capital expenditures	270	213
Depreciation and amortization	2,351	2,335
Civil
Segment Reporting Information [Line Items]
Revenue	349,870	390,795
Civil | Unfavorable Legal Ruling Pertaining to Mass-Transit Project in California
Segment Reporting Information [Line Items]
Loss contingency	28,000	17,600
Loss contingency, after tax	$ 22,200	$ 13,900
Loss contingency, after tax, diluted (in dollars per share)	$ 0.43	$ 0.27
Civil | Adverse Legal Ruling Pertaining to Bridge Project in New York
Segment Reporting Information [Line Items]
Loss contingency		$ 25,500
Loss contingency, after tax		$ 18,300
Loss contingency, after tax, diluted (in dollars per share)		$ 0.36
Civil | Operating Segments
Segment Reporting Information [Line Items]
Revenue	$ 378,224	$ 460,742
Income (loss) from construction operations	18,012	(967)
Capital expenditures	15,065	11,175
Depreciation and amortization	6,981	17,000
Civil | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(28,354)	(69,947)
Building
Segment Reporting Information [Line Items]
Revenue	229,653	330,648
Building | Adverse Legal Ruling Pertaining to Transit Project in New York
Segment Reporting Information [Line Items]
Loss contingency	72,200
Building | Operating Segments
Segment Reporting Information [Line Items]
Revenue	229,291	355,978
Income (loss) from construction operations	(70,209)	9,464
Capital expenditures	2,017	2
Depreciation and amortization	457	401
Building | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	362	(25,330)
Specialty Contractors
Segment Reporting Information [Line Items]
Revenue	196,777	230,711
Specialty Contractors | Adverse Legal Ruling Pertaining to Transit Project in New York
Segment Reporting Information [Line Items]
Loss contingency	11,400
Specialty Contractors | Operating Segments
Segment Reporting Information [Line Items]
Revenue	196,748	230,864
Income (loss) from construction operations	(12,448)	(3,894)
Capital expenditures	444	638
Depreciation and amortization	619	502
Specialty Contractors | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	$ 29	$ (153)