Transactions, Deconsolidations, Closures and Sales - Summary of Amounts Recognized as of Acquisition Date for Each Major Class of Assets and Liabilities (Detail) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Apr. 30, 2014
Aug. 31, 2014
Sep. 30, 2014
Current assets            
Goodwill $ 902,391 $ 745,036 $ 706,495      
Intangible assets 34,500          
Fort Worth Endoscopy Center [Member]            
Current assets            
Cash and cash equivalents       44    
Accounts receivable       779    
Other current assets       1,488    
Total current assets       2,311    
Property and equipment       1,954    
Goodwill       33,807    
Intangible assets       8,902    
Total assets       46,974    
Current liabilities            
Accounts payable and other current liabilities       1,425    
Total current liabilities       1,425    
Other long-term liabilities       85    
Total liabilities       1,510    
Surgery Center of Rockville L.L.C. [Member]            
Current assets            
Cash and cash equivalents         19  
Accounts receivable         284  
Other current assets         26  
Total current assets         329  
Property and equipment         1,399  
Goodwill         14,494  
Intangible assets         2,655  
Total assets         18,877  
Current liabilities            
Accounts payable and other current liabilities         65  
Total current liabilities         65  
Other long-term liabilities         91  
Total liabilities         156  
Marina del Rey ASC And Newport Beach ASC [Member]            
Current assets            
Cash and cash equivalents           861
Accounts receivable           2,504
Other current assets           525
Total current assets           3,890
Property and equipment           3,709
Goodwill           43,878
Intangible assets           8,640
Total assets           60,117
Current liabilities            
Accounts payable and other current liabilities           474
Total current liabilities           474
Other long-term liabilities           990
Total liabilities           1,464
Specialty Surgical Center L L C            
Current assets            
Cash and cash equivalents 706          
Accounts receivable 1,130          
Other current assets 19          
Total current assets 1,855          
Property and equipment 1,002          
Goodwill 36,865          
Intangible assets 4,958          
Total assets 44,680          
Current liabilities            
Accounts payable and other current liabilities 904          
Total current liabilities 904          
Other long-term liabilities 59          
Total liabilities 963          
Remaining Nine Acquisitions [Member]            
Current assets            
Cash and cash equivalents 1,266          
Accounts receivable 3,852          
Other current assets 1,008          
Total current assets 6,126          
Property and equipment 11,628          
Goodwill 48,682          
Intangible assets 9,342          
Total assets 75,778          
Current liabilities            
Accounts payable and other current liabilities 3,113          
Total current liabilities 3,113          
Other long-term liabilities 14,106          
Total liabilities 17,219          
Five Acquisitions [Member]            
Current assets            
Cash and cash equivalents   4,546        
Accounts receivable   4,512        
Other current assets   716        
Total current assets   9,774        
Property and equipment   5,890        
Goodwill   50,436        
Intangible assets   20,333        
Total assets   90,793        
Current liabilities            
Accounts payable and other current liabilities   4,002        
Total current liabilities   4,002        
Other long-term liabilities   677        
Total liabilities   4,679        
Investment in and advances to nonconsolidated affiliates   $ 4,360