XML 69 R51.htm IDEA: XBRL DOCUMENT v3.8.0.1
Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Goodwill And Other Intangible Assets [Line Items]      
Goodwill $ 4,283,963 $ 3,845,157  
Change in goodwill carrying amount 438,800    
Goodwill deductible for tax purpose 159,500    
Intangible assets related to acquisitions 39,400    
Amortization expense for intangible assets $ 68,900 $ 60,300 $ 42,000
Physician And Hospital Agreements [Member]      
Goodwill And Other Intangible Assets [Line Items]      
Weighted average amortization period 10 years