Revisions in Estimates (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Change in Accounting Estimate [Line Items]
Amount Considered Significant to Individual Project Gross Profit	$ 21,400,000	$ 13,500,000	$ 50,000,000	$ 28,800,000
Financial Effect on Future Periods	0		0
Construction [Member]
Change in Accounting Estimate [Line Items]
Amount Considered Significant to Individual Project Gross Profit	1,000,000
Increase (Decrease) on Project Profitability	(1,000,000)	1,500,000	(9,400,000)	600,000
Contracts Accounted for under Percentage of Completion [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability	(8,500,000)	(6,800,000)	25,900,000	13,600,000
Contracts Accounted for under Percentage of Completion [Member] | Large Project Construction [Member] | Noncontrolling Interest [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability	1,800,000	5,900,000	5,800,000	4,300,000
Upward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes	0	4	2	5
Range Of Effect On Gross Profit	0
Increase (Decrease) on Project Profitability	0	7,400,000	2,200,000	11,800,000
Upward Estimate Change [Member] | Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit		(1,300,000)	(1,100,000)	(1,100,000)
Upward Estimate Change [Member] | Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit		(2,700,000)	(1,200,000)	(3,000,000)
Upward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes	2	3	9	6
Increase (Decrease) on Project Profitability	5,100,000	12,900,000	43,000,000	47,500,000
Upward Estimate Change [Member] | Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	(1,300,000)	(1,000,000)	(1,100,000)	(2,100,000)
Upward Estimate Change [Member] | Large Project Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	(3,800,000)	(10,500,000)	(11,800,000)	(26,600,000)
Downward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes	1	3	5	4
Range Of Effect On Gross Profit	(1,000,000)
Increase (Decrease) on Project Profitability	1,000,000	5,900,000	11,600,000	11,200,000
Downward Estimate Change [Member] | Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit		(1,500,000)	1,700,000	1,100,000
Downward Estimate Change [Member] | Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit		(2,500,000)	2,900,000	4,300,000
Downward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes	3	4	3	4
Increase (Decrease) on Project Profitability	(13,600,000)	(19,700,000)	(17,100,000)	(33,900,000)
Downward Estimate Change [Member] | Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	(2,000,000)	1,400,000	(1,300,000)	1,600,000
Downward Estimate Change [Member] | Large Project Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ (7,000,000)	$ 14,700,000	$ (13,900,000)	$ 23,500,000