Revisions in Estimates (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) project	Jun. 30, 2015 USD ($) project	Jun. 30, 2016 USD ($) project	Jun. 30, 2015 USD ($) project
Change in Accounting Estimate [Line Items]
Impact From Affirmative Claim Recovery Estimate	$ 17.4		$ 20.2
Impact from estimated recovery of backcharge claims			7.6	$ 0.0
Construction [Member]
Change in Accounting Estimate [Line Items]
Change in Accounting Estimate Amount Considered Significant to Individual Project Gross Profit	$ 1.0	$ 1.0	$ 1.0	$ 1.0
Downward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes | project	1	2	2	2
Increase (Decrease) on Project Profitability	$ (1.0)	$ (2.6)	$ (2.5)	$ (2.6)
Downward Estimate Change [Member] | Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	(1.0)	(1.1)	(1.2)	(1.2)
Downward Estimate Change [Member] | Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ (1.0)	$ (1.5)	$ (1.3)	$ (1.4)
Downward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes | project	4	3	4	4
Increase (Decrease) on Project Profitability	$ (14.6)	$ (5.7)	$ (20.1)	$ (9.8)
Downward Estimate Change [Member] | Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	(2.2)	(1.2)	(3.4)	(1.4)
Downward Estimate Change [Member] | Large Project Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ (5.9)	$ (2.4)	$ (6.4)	$ (3.4)
Upward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes | project	0	1	0	4
Increase (Decrease) on Project Profitability	$ 0.0	$ 1.3	$ 0.0	$ 6.9
Upward Estimate Change [Member] | Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	0.0	1.3	0.0	1.0
Upward Estimate Change [Member] | Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	$ 0.0	$ 1.3	$ 0.0	$ 2.3
Upward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes | project	2	2	4	3
Increase (Decrease) on Project Profitability	$ 9.8	$ 4.6	$ 12.3	$ 7.3
Upward Estimate Change [Member] | Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	2.9	2.3	1.2	2.1
Upward Estimate Change [Member] | Large Project Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit	6.9	2.3	6.9	2.9
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	(3.6)	(0.5)		(1.0)
Net Downward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability	(1.0)	(1.3)	(2.5)
Net Downward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability	(4.8)	(1.1)	(7.8)	(2.5)
Net Upward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability				4.3
no material associated cost [Member] | customer [Member]
Change in Accounting Estimate [Line Items]
Impact From Affirmative Claim Recovery Estimate	$ 2.1		4.9	$ 9.7
Revisions to Estimated Total Contract Costs [Member] [Member] | customer [Member]
Change in Accounting Estimate [Line Items]
Impact From Affirmative Claim Recovery Estimate		$ 0.0	$ 15.3