Revisions in Estimates (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) project	Sep. 30, 2015 USD ($) project	Sep. 30, 2016 USD ($) project	Sep. 30, 2015 USD ($) project	Dec. 31, 2015 USD ($)
Change in Accounting Estimates
Impact From Affirmative Claim Recovery Estimate	$ 1,200,000	$ 35,000,000	$ 21,400,000	$ 44,700,000
Impact From Estimated Recovery of Backcharge Claims	3,300,000	0	10,900,000	0
Unconsolidated Joint Venture Back charges claims	5,900,000	0	5,900,000	0	$ 0
Construction Segment
Change in Accounting Estimates
Change in Accounting Estimate Amount Considered Significant to Individual Project Gross Profit	$ 1,000,000	$ 1,000,000	$ 1,000,000	$ 1,000,000
Downward Estimate Changes | Construction Segment
Change in Accounting Estimates
Number of Projects with Estimate Changes | project	1	1	5	3
Increase (Decrease) on Project Profitability	$ (1,900,000)	$ (1,400,000)	$ (7,600,000)	$ (5,900,000)
Downward Estimate Changes | Construction Segment | Minimum
Change in Accounting Estimates
Range Of Effect On Gross Profit	(1,900,000)	(1,400,000)	(1,100,000)	(1,500,000)
Downward Estimate Changes | Construction Segment | Maximum
Change in Accounting Estimates
Range Of Effect On Gross Profit	$ (1,900,000)	$ (1,400,000)	$ (2,600,000)	$ (2,300,000)
Downward Estimate Changes | Large Project Construction Segment
Change in Accounting Estimates
Number of Projects with Estimate Changes | project	3	2	4	5
Increase (Decrease) on Project Profitability	$ (5,700,000)	$ (4,400,000)	$ (25,800,000)	$ (18,100,000)
Downward Estimate Changes | Large Project Construction Segment | Minimum
Change in Accounting Estimates
Range Of Effect On Gross Profit	(1,100,000)	(1,800,000)	(3,400,000)	(2,600,000)
Downward Estimate Changes | Large Project Construction Segment | Maximum
Change in Accounting Estimates
Range Of Effect On Gross Profit	$ (3,500,000)	$ (2,600,000)	$ (7,900,000)	$ (4,600,000)
Upward Estimate Changes | Construction Segment
Change in Accounting Estimates
Number of Projects with Estimate Changes | project	1	1	2	7
Increase (Decrease) on Project Profitability	$ 2,600,000	$ 5,100,000	$ 4,500,000	$ 15,300,000
Upward Estimate Changes | Construction Segment | Minimum
Change in Accounting Estimates
Range Of Effect On Gross Profit	2,600,000	5,100,000	1,800,000	1,000,000
Upward Estimate Changes | Construction Segment | Maximum
Change in Accounting Estimates
Range Of Effect On Gross Profit	$ 2,600,000	$ 5,100,000	$ 2,700,000	$ 5,000,000
Upward Estimate Changes | Large Project Construction Segment
Change in Accounting Estimates
Number of Projects with Estimate Changes | project	3	4	7	7
Increase (Decrease) on Project Profitability	$ 6,100,000	$ 9,400,000	$ 19,800,000	$ 19,900,000
Upward Estimate Changes | Large Project Construction Segment | Minimum
Change in Accounting Estimates
Range Of Effect On Gross Profit	1,400,000	1,000,000	1,200,000	1,500,000
Upward Estimate Changes | Large Project Construction Segment | Maximum
Change in Accounting Estimates
Range Of Effect On Gross Profit	3,000,000	3,900,000	6,500,000	5,100,000
Net Downward Estimate Changes | Construction Segment
Change in Accounting Estimates
Increase (Decrease) on Project Profitability			(3,100,000)
Net Downward Estimate Changes | Large Project Construction Segment
Change in Accounting Estimates
Increase (Decrease) on Project Profitability			(6,000,000)
Net Downward Estimate Changes | Large Project Construction Segment | Noncontrolling Interest [Member]
Change in Accounting Estimates
Increase (Decrease) on Project Profitability	0		(3,500,000)
Net Upward Estimate Changes | Construction Segment
Change in Accounting Estimates
Increase (Decrease) on Project Profitability	700,000	3,700,000		9,400,000
Net Upward Estimate Changes | Large Project Construction Segment
Change in Accounting Estimates
Increase (Decrease) on Project Profitability	400,000	5,000,000		1,800,000
Net Upward Estimate Changes | Large Project Construction Segment | Noncontrolling Interest [Member]
Change in Accounting Estimates
Increase (Decrease) on Project Profitability		1,400,000		300,000
Estimated costs recorded in prior period
Change in Accounting Estimates
Impact From Affirmative Claim Recovery Estimate	1,000,000	1,900,000	5,900,000	11,600,000
Impact From Estimated Recovery of Backcharge Claims		2,100,000		7,500,000
Revisions to estimated total contract costs
Change in Accounting Estimates
Impact From Affirmative Claim Recovery Estimate	$ 200,000		$ 15,500,000	33,100,000
Impact From Estimated Recovery of Backcharge Claims		$ 1,200,000		$ 3,400,000