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Employee Benefit Plans (Collective Bargaining Agreements and Multiemployer Pension Plans) (Details)
$ in Millions
12 Months Ended
Dec. 31, 2018
USD ($)
pension_plan
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Defined Benefit Plan Disclosure [Line Items]      
Approximate percent of our workforce represented by various labor unions 24.00%    
Approximate percent of our workforce covered by collective bargaining agreements 6.00%    
Number of multi-employer pension plans under collective bargaining agreements in which company contributes | pension_plan 26    
Approximate percentage of our total current employees that are participants in multi-employer pension plans 18.00%    
Contributions to pension plan amount considered to be significant $ 69.4 $ 64.7 $ 59.7
Percentage of funded status of pension protection act critical zone maximum (up to) 65.00%    
Percentage of funded status of pension protection act endangered zone maximum (less than) 80.00%    
Percentage of funded status of pension protection act Safe zone minimum (at least) 80.00%    
Percent of total contributions that we are listed as providing more than for Local 731 Private Scavengers and Garage Attendants Pension Trust Fund 5.00%    
Multiemployer Plan      
Defined Benefit Plan Disclosure [Line Items]      
Contributions to pension plan amount considered to be significant $ 2.0