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Revenue Recognition (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2018
Jan. 01, 2018
Dec. 31, 2017
Disaggregation of Revenue [Abstract]        
Contract liability $ 138.5 $ 138.5   $ 126.1
Contract liability, revenue recognized 6.0 11.7    
Contract asset $ 9.2 $ 9.2 $ 9.2