Business Segments (Reportable Segments) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Revenue	$ 1,070,926	$ 1,178,222	$ 2,884,107	$ 3,605,060
Income (loss) from construction operations	(6,892)	52,093	(107,353)	170,550
Capital expenditures	13,964	8,302	42,809	27,162
Depreciation and amortization	15,533	30,061	54,054	92,196
Favorable Legal Ruling Pertaining to Electrical Project in New York
Segment Reporting Information [Line Items]
Income (loss) from construction operations				(14,500)
Gain (loss) related to additional revenue recognized, after tax				$ (10,500)
Gain (loss) additional revenue recognized , after tax, per share, diluted (in dollars per share)				$ (0.21)
Operating Segments
Segment Reporting Information [Line Items]
Revenue	1,157,793	1,290,878	3,111,612	$ 3,996,366
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(86,867)	(112,656)	(227,505)	(391,306)
Corporate
Segment Reporting Information [Line Items]
Revenue	0	0
Income (loss) from construction operations	(17,898)	(15,778)	(46,397)	(42,511)
Capital expenditures	423	234	931	626
Depreciation and amortization	2,368	2,634	7,063	8,171
Civil
Segment Reporting Information [Line Items]
Revenue	500,905	546,218	1,295,322	1,577,145
Income (loss) from construction operations				18,100
Gain (loss) related to additional revenue recognized, after tax				$ 13,000
Gain (loss) additional revenue recognized , after tax, per share, diluted (in dollars per share)				$ 0.25
Civil | Unfavorable Legal Ruling Pertaining To Mass-Transit Project In California
Segment Reporting Information [Line Items]
Loss contingency			(34,600)
Loss contingency, after tax			$ (27,300)
Loss contingency, after tax, diluted (in dollars per share)			$ (0.53)
Civil | Adverse Legal Ruling Pertaining to Bridge Project in the Northeast
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 | Unfavorable Settlement due to Project in Maryland
Segment Reporting Information [Line Items]
Loss contingency			$ (16,200)
Loss contingency, after tax			$ (11,600)
Loss contingency, after tax, diluted (in dollars per share)			$ (0.23)
Civil | Unfavorable Adjustment Due to Civil Segment Highway Project in the Northeast
Segment Reporting Information [Line Items]
Loss contingency			$ (14,300)
Loss contingency, after tax			$ (10,200)
Loss contingency, after tax, diluted (in dollars per share)			$ (0.20)
Civil | Unfavorable Adjustments Due to Civil Segment Mass-transit Project in California
Segment Reporting Information [Line Items]
Loss contingency			$ (13,100)
Loss contingency, after tax			$ (9,400)
Loss contingency, after tax, diluted (in dollars per share)			$ (0.18)
Civil | Operating Segments
Segment Reporting Information [Line Items]
Revenue	564,205	624,549	$ 1,478,162	$ 1,850,748
Income (loss) from construction operations	22,786	62,555	12,052	187,733
Capital expenditures	11,872	7,847	38,703	26,027
Depreciation and amortization	12,166	26,234	44,191	80,125
Civil | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(63,300)	(78,331)	(182,840)	(273,603)
Building
Segment Reporting Information [Line Items]
Revenue	318,050	360,941	915,639	1,150,834
Building | Operating Segments
Segment Reporting Information [Line Items]
Revenue	341,614	395,013	960,148	1,267,984
Income (loss) from construction operations	56	10,786	9,453	19,514
Capital expenditures	921	87	973	211
Depreciation and amortization	470	416	1,261	1,272
Building | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(23,564)	(34,072)	(44,509)	(117,150)
Specialty Contractors
Segment Reporting Information [Line Items]
Revenue	251,971	271,063	673,146	877,081
Specialty Contractors | Unfavorable Adjustment due to Electrical Project in the Northeast
Segment Reporting Information [Line Items]
Loss contingency	(14,300)		(36,000)
Loss contingency, after tax	$ (10,200)		$ (26,000)
Loss contingency, after tax, diluted (in dollars per share)	$ (0.20)		$ (0.51)
Specialty Contractors | Unfavorable Legal Appeal due to Electrical Project in the Northeast
Segment Reporting Information [Line Items]
Loss contingency			$ (17,800)
Loss contingency, after tax			$ (12,800)
Loss contingency, after tax, diluted (in dollars per share)			$ (0.25)
Specialty Contractors | Favorable Legal Ruling Pertaining to Electrical Project in New York
Segment Reporting Information [Line Items]
Favorable arbitration				20,100
Favorable arbitration, after tax				$ 14,600
Favorable arbitration, after tax, diluted (in dollars per share)				$ 0.28
Specialty Contractors | Operating Segments
Segment Reporting Information [Line Items]
Revenue	$ 251,974	271,316	$ 673,302	$ 877,634
Income (loss) from construction operations	(11,836)	(5,470)	(82,461)	5,814
Capital expenditures	748	134	2,202	298
Depreciation and amortization	529	777	1,539	2,628
Specialty Contractors | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(3)	(253)	(156)	(553)
Total
Segment Reporting Information [Line Items]
Revenue	1,070,926	1,178,222	2,884,107	3,605,060
Total | Operating Segments
Segment Reporting Information [Line Items]
Revenue	1,157,793	1,290,878	3,111,612	3,996,366
Income (loss) from construction operations	11,006	67,871	(60,956)	213,061
Capital expenditures	13,541	8,068	41,878	26,536
Depreciation and amortization	13,165	27,427	46,991	84,025
Total | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	$ (86,867)	$ (112,656)	(227,505)	$ (391,306)
Civil and Building | Unfavorable Adjustment due to Changes in Estimates on Transportation Project in the Northeast
Segment Reporting Information [Line Items]
Loss contingency			(18,000)
Loss contingency, after tax			$ (13,900)
Loss contingency, after tax, diluted (in dollars per share)			$ (0.27)