Change in Accounting Principle (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2012
Change in Accounting Principle (Textual) [Abstract]    
Costs related to acquisition $ 9.3 $ 19.0
Change in Accounting Principle (Additional Textual) [Abstract]    
Net result of adoption of new accounting policy 0.8 1.5
Previous Accounting Guidance [Member]
   
Change in Accounting Principle (Textual) [Abstract]    
Costs related to acquisition 8.8 17.5
Impact of Change in Accounting Principle [Member]
   
Change in Accounting Principle (Textual) [Abstract]    
Costs related to acquisition $ 0.6 $ 1.5