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Employee Benefit Plans Summary of ARX Defined Contribution Plan (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Defined Contribution Pension Plan 401k      
Defined Contribution Plan Disclosure [Line Items]      
Matching contributions $ 78.4 $ 74.8 $ 69.9
Defined Contribution Pension Plan Four Zero One K ARX [Domain]      
Defined Contribution Plan Disclosure [Line Items]      
Matching contributions $ 0.0