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Employee Benefit Plans and Other Postretirement Benefits - Additional Information (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Pension Contributions [Abstract]        
Minimum pension contributions     $ 8.0  
Pension Plans        
Pension Contributions [Abstract]        
Contributions to pension plan $ 36.2 $ 49.7 $ 42.1 $ 53.4