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Business Acquisitions - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2015
USD ($)
Acquisition
Company
shares
Dec. 31, 2014
USD ($)
Acquisition
Company
Jun. 30, 2014
JointVenture
Jun. 01, 2014
Business Acquisition [Line Items]        
Number of physician group practices acquired | Company 10 11    
Business acquisition, total consideration $ 853,300,000 $ 488,600,000    
Payments to acquire business, net of cash acquired 818,300,000 479,400,000    
Contingent consideration $ 3,800,000 $ 9,200,000    
Number of anesthesiology practices acquired | Company 7      
Number of neonatology practices acquired | Company 2      
Number of other pediatric subspecialty practices acquired | Company 1      
Number of non-practice acquisitions | Acquisition 2      
Number of business acquired | Acquisition 12 13    
Cash acquired from acquisition $ 23,000,000      
Business acquisition, other current liabilities 400,000      
Payments to acquire business by issue of common stock $ 7,800,000      
Number of shares of common stock issued | shares 114,306      
Time period for achievement of certain performance measures for payment of contingent consideration, years 2 years      
Assumed payment probability of contingent consideration payment 100.00%      
Range of the undiscounted amount under contingent consideration agreement, low $ 0      
Range of the undiscounted amount under contingent consideration agreement, high 4,000,000      
Contingent consideration decrease in fair value 1,000,000      
Contingent consideration payments related to prior-period acquisitions 14,300,000      
Goodwill 3,366,150,000 $ 2,776,188,000    
Number of joint ventures | JointVenture     2  
Fair value, contribution credit 7,700,000      
Carrying value of goodwill transferred 7,200,000      
Fixed assets transferred 500,000      
Gain or loss from the joint venture transaction $ 0      
Variable Interest Entity, Primary Beneficiary [Member]        
Business Acquisition [Line Items]        
Consolidation method ownership percentage in joint venture 75.00%     75.00%
Unnamed Corporate Joint Venture [Member]        
Business Acquisition [Line Items]        
Equity method ownership percentage in joint venture 37.50%     37.50%
Prior-Period Acquisitions [Member]        
Business Acquisition [Line Items]        
Goodwill $ 600,000      
Other intangible assets 5,300,000      
Other long-term liabilities 2,600,000      
Additional cash consideration related to a working capital 600,000      
Other current assets $ 2,600,000      
Minimum [Member]        
Business Acquisition [Line Items]        
Assumed discount rates for acquisition-date fair value 2.80%      
Maximum [Member]        
Business Acquisition [Line Items]        
Assumed discount rates for acquisition-date fair value 3.50%