Acquisitions and Developments - Acquisition of Symbion (Details) - USD ($)
 12 Months Ended
May 03, 2016
Mar. 31, 2016
Nov. 03, 2014
Jun. 13, 2014
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Mar. 24, 2016
Oct. 07, 2015
Oct. 06, 2015
Jan. 27, 2014
Business Acquisition [Line Items]                        
Acquisition related costs         $ 2,185,000 $ 1,560,000 $ 0          
Capitalized deferred financing costs         1,488,000 2,005,000            
Debt instrument unamortized discount         32,274,000 30,622,000            
Merger transaction costs         8,738,000 17,920,000 21,690,000          
Loss on debt extinguishment         $ 11,876,000 $ 16,102,000 23,414,000          
Line of Credit                        
Business Acquisition [Line Items]                        
Debt maximum borrowing capacity     $ 1,440,000,000.000                 $ 90,000,000.0
Line of Credit | 2014 First Lien Credit Agreement                        
Business Acquisition [Line Items]                        
Debt maximum borrowing capacity     870,000,000.0           $ 950,000,000.0      
Line of Credit | 2014 Second Lien Credit Agreement                        
Business Acquisition [Line Items]                        
Debt maximum borrowing capacity     490,000,000.0                  
Loss on debt extinguishment   $ 8,300,000                    
Line of Credit | 2014 Revolver Loan                        
Business Acquisition [Line Items]                        
Debt maximum borrowing capacity     80,000,000.0             $ 150,000,000.0 $ 80,000,000.0  
Symbion Holdings Corporation                        
Business Acquisition [Line Items]                        
Aggregate purchase price     711,288,000 $ 792,000,000                
Cash consideration     300,100,000                  
Acquisition escrow deposit funded $ 16,600,000   16,200,000                  
Debt assumed for acquiree     472,400,000                  
Acquisition related costs             93,300,000          
Capitalized deferred financing costs             5,300,000          
Business acquisition transaction costs             21,700,000          
Debt instrument unamortized discount             42,900,000          
Debt extinguishment costs             23,400,000          
Goodwill, expected tax deductible amount     $ 142,500,000                  
Merger transaction costs             21,700,000          
Loss on debt extinguishment             $ 23,400,000 $ 9,900,000        
Symbion Holdings Corporation | Payment in Kind (PIK) Note                        
Business Acquisition [Line Items]                        
Debt instrument, stated rate       8.00%