v3.8.0.1
Acquisitions and Noncontrolling Interest - Acquisitions (Details) - USD ($)
$ in Millions
1 Months Ended 12 Months Ended
Oct. 01, 2017
Oct. 31, 2017
Aug. 31, 2017
Dec. 31, 2017
Sep. 30, 2017
Dec. 31, 2016
Jan. 31, 2016
Dec. 31, 2015
Business Acquisition [Line Items]                
Percentage of voting interests acquired             19.00%  
Goodwill       $ 4,749   $ 4,712   $ 842
Fidelis Care                
Business Acquisition [Line Items]                
Definitive agreement to acquire assets, amount         $ 3,750      
Foundation Care                
Business Acquisition [Line Items]                
Percentage of voting interests acquired 80.00%              
Acquisition consideration       59        
Cash consideration   $ 53            
Consideration transfered, present value of future consideration $ 2              
Deferred payment, period of payments 2 years              
Contingent liability $ 4              
Goodwill 37              
Recognized identifiable intangible assets 16              
National Full-Service Specialty Pharmacy                
Business Acquisition [Line Items]                
Contingent consideration based upon meeting performance metrics (not to exceed) $ 32              
U.S. Medical Management                
Business Acquisition [Line Items]                
Percentage of voting interests acquired     32.00%          
Acquisition consideration       $ 86        
Cash consideration     $ 33          
Contingent liability     33          
Settlement of receivable from former noncontrolling interest holder     $ 20