Business Segments (Reportable Segments) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Business Segments
Revenues		$ 1,177,725	$ 1,189,345	$ 1,125,275	$ 958,487	$ 1,183,284	$ 1,123,137	$ 1,120,085	$ 1,028,156	$ 4,450,832		$ 4,454,662	$ 4,757,208
Income (loss) from construction operations		(94,146)	47,943	(341,717)	22,913	90,680	47,306	54,815	(925)	(365,007)		191,876	179,477
Capital Expenditures										84,196		77,069	30,280
Depreciation and amortization	[1]									65,044		47,267	51,930
Goodwill, Impairment Loss										379,863
Net income (loss)		$ (76,229)	$ 26,721	$ (315,439)	$ 4,722	$ 55,391	$ 25,436	$ 27,896	$ (10,942)	$ (360,225)		$ 97,781	$ 154,544
Earnings Per Share, Diluted		$ (1.71)	$ 0.38	$ (6.38)	$ (0.01)	$ 0.98	$ 0.42	$ 0.49	$ (0.24)	$ (7.72)		$ 1.66	$ 2.92
Gain on remeasurement of investment in joint venture										$ 37,792
Intersubsegment Eliminations [Member]
Business Segments
Revenues										(297,756)		$ (229,342)	$ (295,521)
External and Intersegment Customers [Member]
Business Segments
Revenues										4,748,588		4,684,004	5,052,729
Reportable Segments [Member]
Business Segments
Revenues										4,450,832		4,454,662	4,757,208
Income (loss) from construction operations										(299,819)	[2]	255,625	245,344	[3]
Capital Expenditures										83,362		76,298	28,682
Depreciation and amortization	[1]									53,975		35,999	40,487
Reportable Segments [Member] | Intersubsegment Eliminations [Member]
Business Segments
Revenues										(297,756)		(229,342)	(295,521)
Reportable Segments [Member] | External and Intersegment Customers [Member]
Business Segments
Revenues										4,748,588		4,684,004	5,052,729
Civil [Member]
Business Segments
Revenues										1,779,352		1,586,093	1,602,175
Income (loss) from construction operations										(150,837)	[2]	168,256	192,207	[3]
Capital Expenditures										82,156		73,866	27,694
Depreciation and amortization	[1]									47,905		29,685	33,767
Goodwill, Impairment Loss										210,215
Civil [Member] | Intersubsegment Eliminations [Member]
Business Segments
Revenues										(274,745)		(224,139)	(253,989)
Civil [Member] | External and Intersegment Customers [Member]
Business Segments
Revenues										2,054,097		1,810,232	1,856,164
Building [Member]
Business Segments
Revenues										1,742,040		1,861,699	1,941,325
Income (loss) from construction operations										23,655	[2]	43,939	34,199	[3]
Capital Expenditures										518		1,655	267
Depreciation and amortization	[1]									1,934		1,956	2,021
Goodwill, Impairment Loss										13,455
Building [Member] | Intersubsegment Eliminations [Member]
Business Segments
Revenues										(22,713)		(5,203)	(41,532)
Building [Member] | External and Intersegment Customers [Member]
Business Segments
Revenues										1,764,753		1,866,902	1,982,857
Specialty Contractors [Member]
Business Segments
Revenues										929,440		1,006,870	1,213,708
Income (loss) from construction operations										(172,637)	[2]	43,430	18,938	[3]
Capital Expenditures										688		777	721
Depreciation and amortization	[1]									4,136		4,358	4,699
Goodwill, Impairment Loss										156,193
Specialty Contractors [Member] | Intersubsegment Eliminations [Member]
Business Segments
Revenues										(298)
Specialty Contractors [Member] | External and Intersegment Customers [Member]
Business Segments
Revenues										929,738		1,006,870	1,213,708
Corporate [Member]
Business Segments
Income (loss) from construction operations	[4]									(65,188)	[2]	(63,749)	(65,867)	[3]
Capital Expenditures										834		771	1,598
Depreciation and amortization	[1]									11,069		11,268	$ 11,443
Unfavorable Adjustments [Member]
Business Segments
Goodwill, Impairment Loss										379,900
Net income (loss)										$ 330,500
Earnings Per Share, Diluted										$ 6.58
Unfavorable Adjustments [Member] | Alaskan Way Viaduct Matter [Member]
Business Segments
Income (loss) from construction operations										$ 166,800
Income from construction operations, net of tax										$ 119,400
Earnings Per Share, Diluted										$ 2.38
Unfavorable Adjustments [Member] | Civil [Member]
Business Segments
Income (loss) from construction operations												17,800
Income from construction operations, net of tax												$ 12,800
Earnings Per Share, Diluted												$ 0.25
One-Time Gain From Remeasurement [Member]
Business Segments
Earnings Per Share, Diluted										$ 0.54
Gain on remeasurement of investment in joint venture										$ 37,800
Gain on remeasurement of investment in joint venture, net of tax										$ 27,100

[1] Depreciation and amortization is included in income (loss) from construction operations.(d)During the year ended December 31, 2018, the Company recorded a charge of $17.8 million in income (loss) from construction operations (an after-tax impact of $12.8 million, or $0.25 per diluted share), which was primarily non-cash, as a result of the unexpected adverse outcome of an arbitration decision related to a subcontract back charge dispute on a Civil segment project in New York that was completed in 2013.

[2] During the year ended December 31, 2019, the Company recorded a non-cash goodwill impairment charge of $379.9 million in income (loss) from construction operations (an after-tax impact of $330.5 million, or $6.58 per diluted share) resulting from an interim impairment test the Company performed as of June 1, 2019. For further information and breakdown of the goodwill impairment charge by segment, see Note 6. In addition, during the year ended December 31, 2019 the Company recorded a charge of $166.8 million in income (loss) from construction operations (an after-tax impact of $119.4 million, or $2.38 per diluted share), which principally impacted the Civil segment, as a result of the adverse jury verdict on the Alaskan Way Viaduct Matter, as discussed in Note 8. Lastly, the Company recognized a one-time gain of $37.8 million (an after-tax impact of $27.1 million, or $0.54 per diluted share) in Civil segment general and administrative expenses related to a remeasurement of its investment in a joint venture (see Note 13).

[3] During the year ended December 31, 2018, the Company recorded a charge of $17.8 million in income (loss) from construction operations (an after-tax impact of $12.8 million, or $0.25 per diluted share), which was primarily non-cash, as a result of the unexpected adverse outcome of an arbitration decision related to a subcontract back charge dispute on a Civil segment project in New York that was completed in 2013.

[4] Consists primarily of corporate general and administrative expenses.