Revisions in Estimates (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) project	Jun. 30, 2014 USD ($) project	Jun. 30, 2015 USD ($) project	Jun. 30, 2014 USD ($) project
Change in Accounting Estimate [Line Items]
Amount Considered Significant to Individual Project Gross Profit	$ 7.2	$ 24.5	$ 13.4	$ 28.6
Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability	(1.3)	(1.4)	4.3	(8.3)
Contracts Accounted for under Percentage of Completion [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability	(1.1)	25.7	(2.5)	34.5
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	$ (0.5)	$ 8.2	$ (1.0)	$ 7.5
Upward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes | project	1	0	4	0
Increase (Decrease) on Project Profitability	$ 1.3	$ 0.0	$ 6.9	$ 0.0
Upward Estimate Change [Member] | Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	(1.3)	0.0	(1.0)	0.0
Upward Estimate Change [Member] | Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ 0.0	$ 0.0	$ (2.3)	$ 0.0
Upward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes | project	2	6	3	9
Increase (Decrease) on Project Profitability	$ 4.6	$ 28.0	$ 7.3	$ 41.3
Upward Estimate Change [Member] | Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	(2.3)	(1.1)	(2.1)	(1.1)
Upward Estimate Change [Member] | Large Project Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ (2.3)	$ (19.7)	$ (2.9)	$ (16.3)
Downward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes | project	2	1	2	5
Increase (Decrease) on Project Profitability	$ (2.6)	$ 1.4	$ (2.6)	$ 8.3
Downward Estimate Change [Member] | Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	1.1	1.4	1.2	1.1
Downward Estimate Change [Member] | Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ 1.5	$ 0.0	$ 1.4	$ 2.2
Downward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes | project	3	1	4	1
Increase (Decrease) on Project Profitability	$ (5.7)	$ (2.3)	$ (9.8)	$ (6.8)
Downward Estimate Change [Member] | Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	1.2	2.3	1.4	6.8
Downward Estimate Change [Member] | Large Project Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ 2.4	$ 0.0	$ 3.4	$ 0.0