Business Segments (Reportable Segments) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Information [Line Items]
Revenue	$ 1,021,751	$ 861,027	$ 1,798,051	$ 1,813,181
Income (loss) from construction operations	2,388	(90,554)	(79,557)	(100,461)
Capital expenditures	12,827	16,817	30,623	28,845
Depreciation and amortization	10,346	18,283	20,754	38,521
Adverse Legal Ruling Pertaining to Mixed-Use 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)			$ 1.16
Operating Segments
Segment Reporting Information [Line Items]
Revenue	1,013,809	906,235	$ 1,818,072	1,953,819
Income (loss) from construction operations	21,744	(76,565)	(42,901)	(71,962)
Capital expenditures	11,357	16,522	28,883	28,337
Depreciation and amortization	8,151	15,923	16,208	33,826
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	7,942	(45,208)	(20,021)	(140,638)
Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Income (loss) from construction operations	(19,356)	(13,989)	(36,656)	(28,499)
Capital expenditures	1,470	295	1,740	508
Depreciation and amortization	2,195	2,360	4,546	4,695
Civil
Segment Reporting Information [Line Items]
Revenue	554,123	403,622	903,993	794,417
Civil | Unfavorable Legal Ruling Pertaining to Mass-Transit Project in California
Segment Reporting Information [Line Items]
Favorable arbitration	58,100
Favorable arbitration, after tax	$ 46,100
Favorable arbitration, after tax, diluted (in dollars per share)	$ 0.89
Loss contingency			(30,100)	29,100
Loss contingency, after tax			$ (23,900)	$ 22,900
Loss contingency, after tax, diluted (in dollars per share)			$ (0.46)	$ 0.45
Civil | Unfavorable Settlement due to Project in Maryland
Segment Reporting Information [Line Items]
Loss contingency		16,200		$ 16,200
Loss contingency, after tax		$ 11,600		$ 11,600
Loss contingency, after tax, diluted (in dollars per share)		$ 0.23		$ 0.23
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	$ 555,553	$ 453,215	$ 933,777	$ 913,957
Income (loss) from construction operations	105,407	(9,767)	123,419	(10,734)
Capital expenditures	9,643	15,656	24,708	26,831
Depreciation and amortization	7,074	15,025	14,055	32,025
Civil | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(1,430)	(49,593)	(29,784)	(119,540)
Building
Segment Reporting Information [Line Items]
Revenue	331,342	266,941	560,995	597,589
Building | Adverse Legal Ruling Pertaining to Mixed-Use Project in New York
Segment Reporting Information [Line Items]
Loss contingency			72,200
Building | Operating Segments
Segment Reporting Information [Line Items]
Revenue	321,933	262,556	551,224	618,534
Income (loss) from construction operations	(13,831)	(67)	(84,040)	9,397
Capital expenditures	1,458	50	3,475	52
Depreciation and amortization	455	390	912	791
Building | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	9,409	4,385	9,771	(20,945)
Specialty Contractors
Segment Reporting Information [Line Items]
Revenue	136,286	190,464	333,063	421,175
Specialty Contractors | Unfavorable Adjustment due to Changes in Estimates on Transportation Project in the Northeast
Segment Reporting Information [Line Items]
Loss contingency	35,800		35,800
Loss contingency, after tax	$ 26,000		$ 26,000
Loss contingency, after tax, diluted (in dollars per share)	$ 0.50		$ 0.50
Specialty Contractors | Unfavorable Adjustment due to Educational Facilities Project in New York
Segment Reporting Information [Line Items]
Loss contingency	$ 24,700		$ 24,700
Loss contingency, after tax	$ 18,000		$ 18,000
Loss contingency, after tax, diluted (in dollars per share)	$ 0.35		$ 0.35
Specialty Contractors | Unfavorable Adjustment due to Electrical Project in the Northeast
Segment Reporting Information [Line Items]
Loss contingency		33,500		33,500
Loss contingency, after tax		$ 24,200		$ 24,200
Loss contingency, after tax, diluted (in dollars per share)		$ 0.47		$ 0.47
Specialty Contractors | Legal Appeal due to Electrical Project in New York
Segment Reporting Information [Line Items]
Loss contingency		$ 17,800		$ 17,800
Loss contingency, after tax		$ 12,800		$ 12,800
Loss contingency, after tax, diluted (in dollars per share)		$ 0.25		$ 0.25
Specialty Contractors | Adverse Legal Ruling Pertaining to Mixed-Use Project in New York
Segment Reporting Information [Line Items]
Loss contingency			$ 11,400
Specialty Contractors | Operating Segments
Segment Reporting Information [Line Items]
Revenue	$ 136,323	$ 190,464	333,071	$ 421,328
Income (loss) from construction operations	(69,832)	(66,731)	(82,280)	(70,625)
Capital expenditures	256	816	700	1,454
Depreciation and amortization	622	508	1,241	1,010
Specialty Contractors | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(37)	$ 0	(8)	(153)
Civil and Building | Unfavorable Adjustment due to Changes in Estimates on Transportation Project in the Northeast
Segment Reporting Information [Line Items]
Loss contingency	13,100		13,100	14,600
Loss contingency, after tax	$ 10,200		$ 10,200	$ 11,200
Loss contingency, after tax, diluted (in dollars per share)	$ 0.20		$ 0.20	$ 0.22