Business Acquisitions - Additional Information (Detail) (USD $)
3 Months Ended
Mar. 31, 2015
Company
Mar. 31, 2014
Dec. 31, 2014
Business Acquisition [Line Items]      
Number of physician group practices acquired 3    
Business acquisition, total consideration $ 37,100,000    
Goodwill 2,813,673,000   2,776,188,000
Other intangible assets 4,800,000    
Other liabilities 1,300,000    
Contingent consideration payments related to prior-period acquisitions 400,000 3,400,000  
Goodwill deductible for tax purposes 10,800,000    
Three Physician Group Practices Acquisition [Member]      
Business Acquisition [Line Items]      
Goodwill 33,600,000    
Prior-Period Acquisitions [Member]      
Business Acquisition [Line Items]      
Goodwill 3,900,000    
Other intangible assets 5,300,000    
Other liabilities 2,000,000    
Additional cash consideration related to a working capital $ 600,000