Operating Leases (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Lease
Dec. 31, 2014
USD ($)
Leases [Abstract]      
Number of operating leases terminated | Lease   4  
Liability accrued from terminating lease contracts   $ 4,600  
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]      
2017 $ 46,517    
2018 42,917    
2019 39,181    
2020 34,415    
2021 28,728    
Thereafter 143,558    
Total minimum operating lease payments 335,316    
Operating Leased Assets [Line Items]      
Operating leases expense 47,300 40,100 $ 18,800
Operating Leases, Rent Expense, Net [Abstract]      
2017 1,101    
2018 1,137    
2019 658    
2020 468    
2021 312    
Thereafter 1,919    
Total non-cancellable sub-lease income 5,595    
Operating lease agreements, with physician investors      
Operating Leased Assets [Line Items]      
Operating leases expense $ 14,400 $ 12,900 $ 6,900