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Commitments and Contingencies - Narrative (Details)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
USD ($)
employee
collective_bargaining_agreement
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Loss Contingencies [Line Items]      
Rent expense for operating leases and other rental items $ 158,800 $ 143,100 $ 122,000
Sublease rental income $ 600 600 1,200
Number of collective bargaining agreements that are national or regional in scope | collective_bargaining_agreement 2    
Restructuring expenses $ 1,577 1,438 824
Restructuring reserve $ 492 $ 201 $ 81
Minimum      
Loss Contingencies [Line Items]      
Number of employees | employee 32,000    
Number of collective bargaining agreements between our individual subsidiaries and local unions | collective_bargaining_agreement 400    
Surety Bond [Member]      
Loss Contingencies [Line Items]      
Aggregate estimated exposure $ 927,300    
Employee Severance [Member]      
Loss Contingencies [Line Items]      
Restructuring expenses 1,516    
Facility Closing [Member]      
Loss Contingencies [Line Items]      
Restructuring expenses $ 61    
Unionized Employees Concentration Risk [Member] | Workforce Subject to Collective Bargaining Arrangements [Member]      
Loss Contingencies [Line Items]      
Percentage of employees represented by unions 57.00%