Business Segments (Reconciliation of Segment Results to Consolidated Income Before Income Taxes) (Details) - USD ($) $ 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
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
Other income, net										6,667		4,256	43,882
Interest expense										(67,494)		(63,519)	(69,384)
INCOME (LOSS) BEFORE INCOME TAXES		(106,717)	$ 32,312	$ (358,339)	$ 6,910	75,152	$ 32,804	$ 39,867	$ (15,210)	(425,834)		132,613	153,975
Assets		4,485,777				4,387,752				4,485,777		4,387,752
Reportable Segments [Member]
Income (loss) from construction operations										(299,819)	[1]	255,625	245,344	[2]
Civil [Member]
Income (loss) from construction operations										(150,837)	[1]	168,256	192,207	[2]
Assets		2,791,402				2,574,326				2,791,402		2,574,326
Building [Member]
Income (loss) from construction operations										23,655	[1]	43,939	34,199	[2]
Assets		995,298				913,746				995,298		913,746
Specialty Contractors [Member]
Income (loss) from construction operations										(172,637)	[1]	43,430	18,938	[2]
Assets		635,180				745,313				635,180		745,313
Corporate [Member]
Income (loss) from construction operations	[3]									(65,188)	[1]	(63,749)	$ (65,867)	[2]
Assets	[4]	$ 63,897				$ 154,367				$ 63,897		$ 154,367

[1] 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).

[2] 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.

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

[4] Consists principally of cash, equipment, tax-related assets and insurance-related assets, offset by the elimination of assets related to intersegment revenue.