Business Segments (Reportable Segments) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Business Segments
Revenue from external customers		$ 4,641,830	$ 5,318,763	$ 4,450,832
Income (loss) from construction operations		226,804	262,344	(365,007)
Capital expenditures		38,594	54,781	84,196
Depreciation and amortization		118,229	107,034	65,044
Goodwill impairment charge	$ 379,900	0	0	379,863
Goodwill impairment charge, after tax				$ 330,500
Goodwill impairment charge, after tax, diluted (in dollars per share)				$ 6.58
Favorable Adjustments Reflecting Improved Profitability On Mass-Transit Project
Business Segments
Favorable arbitration		16,300
Favorable arbitration, after tax		$ 13,500
Favorable arbitration, after tax, diluted (in dollars per share)		$ 0.26
Operating Segments
Business Segments
Revenue from external customers		$ 5,138,702	5,814,687	$ 4,748,588
Income (loss) from construction operations		284,974	316,196	(299,819)
Capital expenditures		37,902	53,839	83,362
Depreciation and amortization		107,716	95,936	53,975
Corporate, Non-Segment
Business Segments
Income (loss) from construction operations		(58,170)	(53,852)	(65,188)
Capital expenditures		692	942	834
Depreciation and amortization		10,513	11,098	11,069
Intersegment Eliminations
Business Segments
Revenue from external customers		(496,872)	(495,924)	(297,756)
Civil
Business Segments
Revenue from external customers		2,095,760	2,199,899	1,779,352
Goodwill impairment charge				210,200
Civil | Favorable Adjustments Reflecting Improved Profitability On Mass-Transit Project
Business Segments
Favorable arbitration		29,000
Favorable arbitration, after tax		$ 20,900
Favorable arbitration, after tax, diluted (in dollars per share)		$ 0.41
Civil | Unfavorable Adjustment Due to Transportation Project
Business Segments
Loss contingency		$ 13,300
Loss contingency, after tax		$ 10,300
Loss contingency, after tax, diluted (in dollars per share)		$ 0.20
Civil | Favorable Remeasurement Of Investment In Joint Venture
Business Segments
Favorable arbitration				37,800
Favorable arbitration, after tax				$ 27,100
Favorable arbitration, after tax, diluted (in dollars per share)				$ 0.54
Civil | Alaskan Way Viaduct Matter
Business Segments
Loss contingency				$ 166,800
Loss contingency, after tax				$ 119,400
Loss contingency, after tax, diluted (in dollars per share)				$ 2.38
Civil | Operating Segments
Business Segments
Revenue from external customers		$ 2,443,828	2,565,210	$ 2,054,097
Income (loss) from construction operations		266,214	245,835	(150,837)
Capital expenditures		37,067	51,044	82,156
Depreciation and amortization		102,723	90,250	47,905
Civil | Intersegment Eliminations
Business Segments
Revenue from external customers		(348,068)	(365,311)	(274,745)
Building
Business Segments
Revenue from external customers		1,428,102	1,984,641	1,742,040
Goodwill impairment charge				13,500
Building | Unfavorable Adjustment Due to Transportation Project
Business Segments
Loss contingency		13,300
Loss contingency, after tax		$ 10,200
Loss contingency, after tax, diluted (in dollars per share)		$ 0.20
Building | Operating Segments
Business Segments
Revenue from external customers		$ 1,574,759	2,114,459	1,764,753
Income (loss) from construction operations		28,721	53,158	23,655
Capital expenditures		359	878	518
Depreciation and amortization		1,677	1,703	1,934
Building | Intersegment Eliminations
Business Segments
Revenue from external customers		(146,657)	(129,818)	(22,713)
Specialty Contractors
Business Segments
Revenue from external customers		1,117,968	1,134,223	929,440
Goodwill impairment charge				156,200
Specialty Contractors | Unfavorable Adjustment Due to Transportation Project
Business Segments
Loss contingency		17,600
Loss contingency, after tax		$ 12,700
Loss contingency, after tax, diluted (in dollars per share)		$ 0.25
Specialty Contractors | Favorable Legal Ruling Pertaining To Electrical Project In New York
Business Segments
Favorable arbitration		$ 20,100
Favorable arbitration, after tax		$ 14,500
Favorable arbitration, after tax, diluted (in dollars per share)		$ 0.28
Specialty Contractors | Unfavorable Adjustments Due to Second Transportation Project
Business Segments
Loss contingency		$ 19,000
Loss contingency, after tax		$ 13,700
Loss contingency, after tax, diluted (in dollars per share)		$ 0.27
Specialty Contractors | Unfavorable Adjustments Due to Mass Transit Project
Business Segments
Loss contingency		$ 16,200
Loss contingency, after tax		$ 11,700
Loss contingency, after tax, diluted (in dollars per share)		$ 0.23
Specialty Contractors | Unfavorable Legal Ruling Pertaining To Mechanical Project In California
Business Segments
Loss contingency			15,200
Loss contingency, after tax			$ 11,000
Loss contingency, after tax, diluted (in dollars per share)			$ 0.22
Specialty Contractors | Adverse Arbitration Ruling Pertaining To Electrical Project In New York
Business Segments
Loss contingency			$ 13,200
Loss contingency, after tax			$ 9,600
Loss contingency, after tax, diluted (in dollars per share)			$ 0.19
Specialty Contractors | Favorable Arbitration Decision
Business Segments
Favorable arbitration			$ 25,700
Favorable arbitration, after tax			$ 18,600
Favorable arbitration, after tax, diluted (in dollars per share)			$ 0.36
Specialty Contractors | Operating Segments
Business Segments
Revenue from external customers		$ 1,120,115	$ 1,135,018	929,738
Income (loss) from construction operations		(9,961)	17,203	(172,637)
Capital expenditures		476	1,917	688
Depreciation and amortization		3,316	3,983	4,136
Specialty Contractors | Intersegment Eliminations
Business Segments
Revenue from external customers		$ (2,147)	$ (795)	$ (298)