Revisions in Estimates (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Change in Accounting Estimate [Line Items]
Financial Effect on Future Periods	$ 0		$ 0
Amount Considered Significant on Individual Project Gross Profit	1,000,000	1,000,000	1,000,000	1,000,000
Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability	(6,000,000)	(1,300,000)	(9,400,000)	1,600,000
Contracts Accounted for under Percentage of Completion [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability	35,900,000	2,700,000	48,900,000	7,900,000
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	5,700,000	1,000,000	6,600,000	600,000
Upward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes	1	2	4	4
Increase (Decrease) on Project Profitability	1,600,000	2,700,000	7,100,000	7,000,000
Upward Estimate Change [Member] | Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	1,600,000	1,300,000	1,000,000	1,100,000
Upward Estimate Change [Member] | Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	1,600,000	1,400,000	3,000,000	2,900,000
Upward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes	8	5	8	6
Increase (Decrease) on Project Profitability	35,900,000	8,800,000	54,700,000	17,700,000
Upward Estimate Change [Member] | Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	1,100,000	1,000,000	1,100,000	1,400,000
Upward Estimate Change [Member] | Large Project Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	12,600,000	2,600,000	16,300,000	4,200,000
Downward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes	4	2	6	3
Increase (Decrease) on Project Profitability	(7,600,000)	(4,000,000)	(16,500,000)	(5,400,000)
Downward Estimate Change [Member] | Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	(1,100,000)	(1,400,000)	(1,100,000)	(1,400,000)
Downward Estimate Change [Member] | Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	(3,900,000)	(2,600,000)	(6,300,000)	(2,600,000)
Downward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes	0	3	2	2
Increase (Decrease) on Project Profitability	0	(6,100,000)	(5,800,000)	(9,800,000)
Downward Estimate Change [Member] | Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	0	(1,700,000)	(1,700,000)	(4,200,000)
Downward Estimate Change [Member] | Large Project Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ 0	$ (2,400,000)	$ (4,100,000)	$ (5,600,000)