Acquisitions and Developments - Purchase Price Allocation (Details) - USD ($)
$ in Thousands
 12 Months Ended
Nov. 03, 2014
Jun. 13, 2014
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Business Acquisition [Line Items]          
Cash consideration     $ 146,405 $ 112,596 $ 263,280
Net assets acquired:          
Excess of fair value over identifiable net assets acquired     1,555,204 $ 1,407,927 $ 1,298,753
Acquisitions          
Business Acquisition [Line Items]          
Cash consideration     135,061    
Fair value of non-controlling interests     27,164    
Aggregate purchase price     162,225    
Net assets acquired:          
Cash and cash equivalents     4,855    
Accounts receivable, net     6,291    
Prepaid expenses and other current assets     517    
Property and equipment     3,921    
Intangible assets     4,475    
Other long-term assets     56    
Accounts payable     (1,490)    
Other current liabilities     (197)    
Current maturities of long-term debt     (3,926)    
Long-term deferred tax liabilities     (172)    
Net assets acquired     14,330    
Excess of fair value over identifiable net assets acquired     $ 147,895    
Symbion Holdings Corporation          
Business Acquisition [Line Items]          
Cash consideration $ 298,857        
Acquisition consideration payable 16,768        
Fair value of non-controlling interests 395,663        
Aggregate purchase price 711,288 $ 792,000      
Net assets acquired:          
Cash and cash equivalents 40,374        
Accounts receivable, net 79,830        
Inventories 18,389        
Prepaid expenses and other current assets 9,876        
Property and equipment 153,179        
Investments in and advances to affiliates 32,728        
Intangible assets 31,534        
Restricted invested assets 316        
Other long-term assets 6,239        
Accounts payable (20,419)        
Accrued payroll and benefits (14,600)        
Other current liabilities (47,229)        
Current maturities of long-term debt (83,805)        
Long-term debt, less current maturities (376,395)        
Long-term deferred tax liabilities (19,853)        
Other long-term liabilities (60,500)        
Net assets acquired (250,336)        
Excess of fair value over identifiable net assets acquired $ 961,624