Revisions in Estimates (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) project	Sep. 30, 2014 USD ($) project	Sep. 30, 2015 USD ($) project	Sep. 30, 2014 USD ($) project
Change in Accounting Estimate [Line Items]
Amount Considered Significant to Individual Project Gross Profit	$ 8.3	$ 21.4	$ 21.6	$ 50.0
Construction [Member]
Change in Accounting Estimate [Line Items]
Amount Considered Significant to Individual Project Gross Profit			1.0
Increase (Decrease) on Project Profitability	(3.7)	1.0	(9.4)	9.3
Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Amount Considered Significant to Individual Project Gross Profit			1.0
Contracts Accounted for under Percentage of Completion [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability	(5.1)	8.5	(1.8)	(25.9)
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	$ 1.4	$ (1.8)	$ 0.3	$ (5.8)
Upward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes | project	1	0	7	2
Increase (Decrease) on Project Profitability	$ (5.1)	$ 0.0	$ (15.3)	$ (2.3)
Upward Estimate Change [Member] | Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	(5.1)	0.0	(1.0)	(1.1)
Upward Estimate Change [Member] | Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ (5.1)	$ 0.0	$ (5.0)	$ (1.2)
Upward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes | project	4	2	7	9
Increase (Decrease) on Project Profitability	$ (9.4)	$ (5.1)	$ (19.9)	$ (43.0)
Upward Estimate Change [Member] | Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	(1.0)	(1.3)	(1.5)	(1.1)
Upward Estimate Change [Member] | Large Project Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ (3.9)	$ (3.8)	$ (5.1)	$ (11.8)
Downward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes | project	1	1	3	5
Increase (Decrease) on Project Profitability	$ 1.4	$ 1.0	$ 5.9	$ 11.6
Downward Estimate Change [Member] | Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	1.4	1.0	1.5	1.7
Downward Estimate Change [Member] | Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ 1.4	$ 1.0	$ 2.3	$ 2.9
Downward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes | project	2	3	5	3
Increase (Decrease) on Project Profitability	$ 4.3	$ 13.6	$ 18.1	$ 17.1
Downward Estimate Change [Member] | Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	1.8	2.0	2.6	1.3
Downward Estimate Change [Member] | Large Project Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ 2.6	$ 7.0	$ 4.6	$ 13.9