Business Segments (Reportable Segments) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Business Segments
Revenues		$ 1,200,830	$ 1,340,739	$ 1,312,438	$ 1,066,465	$ 1,201,877	$ 1,250,689	$ 1,084,510	$ 955,233	$ 4,920,472	$ 4,492,309		$ 4,175,672
Before litigation-related charge										129,273
Litigation-related charge	[1]									(23,860)
INCOME FROM CONSTRUCTION OPERATIONS		15,474	38,974	$ 30,881	$ 20,084	64,396	$ 70,354	$ 65,443	$ 41,497	105,413	241,690		203,822
Capital Expenditures										35,912	75,013		45,291
Assets		4,042,441				3,773,315				4,042,441	3,773,315
External and Intersegment Customers [Member]
Business Segments
Revenues										5,133,715	4,590,227		4,324,919
Intersegment Elimination [Member]
Business Segments
Revenues										(213,243)	(97,918)		(149,247)
Civil [Member]
Business Segments
Revenues										1,889,907	1,687,144		1,441,416
Before litigation-related charge										169,073
Litigation-related charge	[1]									(23,860)
INCOME FROM CONSTRUCTION OPERATIONS										145,213	220,554		177,667
Capital Expenditures										8,383	65,377		32,489
Assets		1,964,674				1,814,170				1,964,674	1,814,170
Civil [Member] | External and Intersegment Customers [Member]
Business Segments
Revenues										2,005,193	1,730,468		1,519,370
Civil [Member] | Intersegment Elimination [Member]
Business Segments
Revenues										(115,286)	(43,324)		(77,954)
Building [Member]
Business Segments
Revenues										1,802,535	1,503,837		1,551,979
Before litigation-related charge										(1,240)
INCOME FROM CONSTRUCTION OPERATIONS										(1,240)	24,697		24,579
Capital Expenditures										2,877	735		1,666
Assets		798,022				680,933				798,022	680,933
Building [Member] | External and Intersegment Customers [Member]
Business Segments
Revenues										1,900,492	1,558,431		1,622,705
Building [Member] | Intersegment Elimination [Member]
Business Segments
Revenues										(97,957)	(54,594)		(70,726)
Specialty Contractors [Member]
Business Segments
Revenues										1,228,030	1,301,328		1,182,277
Before litigation-related charge										15,682
INCOME FROM CONSTRUCTION OPERATIONS										15,682	50,998		49,008
Capital Expenditures										1,193	6,974		4,137
Assets		$ 863,242				$ 775,162				863,242	775,162
Specialty Contractors [Member] | External and Intersegment Customers [Member]
Business Segments
Revenues										1,228,030	1,301,328		1,182,844
Specialty Contractors [Member] | Intersegment Elimination [Member]
Business Segments
Revenues													(567)
Operating Segment [Member]
Business Segments
Revenues										4,920,472	4,492,309		4,175,672
Before litigation-related charge										183,515
Litigation-related charge	[1]									(23,860)
INCOME FROM CONSTRUCTION OPERATIONS										159,655	296,249		251,254
Capital Expenditures										12,453	73,086		38,292
Operating Segment [Member] | External and Intersegment Customers [Member]
Business Segments
Revenues										5,133,715	4,590,227		4,324,919
Operating Segment [Member] | Intersegment Elimination [Member]
Business Segments
Revenues										(213,243)	(97,918)		(149,247)
Corporate Segment [Member]
Business Segments
Before litigation-related charge	[2]									(54,242)
INCOME FROM CONSTRUCTION OPERATIONS										(54,242)	(54,559)	[2]	(47,432)	[2]
Capital Expenditures										$ 23,459	$ 1,927		$ 6,999
Brightwater Matter [Member]
Business Segments
Pre-tax charge			$ 23,900

[1] The Company recorded a non-cash, pre-tax charge of $23.9 million for an adverse appellate court decision related to a long-standing litigation matter for which the Company, as part of a 2011 acquisition, assumed liability as a minority partner in a joint venture for a project that had already been completed. (For further information, refer to the Brightwater Matter discussion in Note 7.)

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