Business Acquisitions (Details 4 ) (USD $)
In Millions, unless otherwise specified
3 Months Ended 1 Months Ended
Mar. 31, 2014
Feb. 28, 2014
Mar. 31, 2015
Dec. 31, 2014
Business Acquisitions        
Cash paid for acquisition, net of cash acquired $ 35.7      
Goodwill     484.5 484.5
Spatial Energy        
Business Acquisitions        
Cash paid for acquisition, net of cash acquired   35.7    
Goodwill associated with acquisition that is deductible for income tax purposes   19.0    
Identifiable intangible assets:   13.9    
Liabilities accrued in consideration for business acquisition   3.9    
Goodwill   $ 25.7