Annual report pursuant to Section 13 and 15(d)

Acquisitions - Narrative (Details)

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Acquisitions - Narrative (Details)
$ / shares in Units, shares in Millions, $ in Millions
 1 Months Ended 6 Months Ended 12 Months Ended
Jan. 23, 2020
USD ($)
$ / shares
shares
Jul. 01, 2018
USD ($)
May 31, 2018
shares
Dec. 31, 2018
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Oct. 31, 2019
$ / shares
Business Acquisition [Line Items]                
Business acquisition, share price (USD per share) | $ / shares               $ 66.76
Department Of Health, State Of New York                
Business Acquisition [Line Items]                
Commitment to undertaking   $ 340            
Commitment to undertaking, term   5 years            
Commitment to undertaking, expensed       $ 328 $ 136      
Public Stock Offering                
Business Acquisition [Line Items]                
Shares issued to fund acquisition (in shares) | shares     53.2          
WellCare                
Business Acquisition [Line Items]                
Total revenues         $ 102,379 $ 88,842    
Fidelis Care                
Business Acquisition [Line Items]                
Total acquisition consideration   $ 3,621            
Revenue of acquiree since acquisition date, actual           5,628    
Total revenues           $ 65,792 $ 58,275  
Subsequent Event                
Business Acquisition [Line Items]                
Business acquisition, share price (USD per share) | $ / shares $ 66.76              
Subsequent Event | WellCare                
Business Acquisition [Line Items]                
Transaction value $ 19,600              
Debt assumed 1,950              
Total acquisition consideration 17,605              
Equity value issued in business acquisition 11,431              
Cash payments to acquire business 6,079              
Fair value adjustment to stock based compensation associated with pre-combination service $ 95              
Common stock converted into right to to Centene common stock 3.38              
Multiplied by the per common share cash consideration | $ / shares $ 120.00              
Shares issued in business acquisition (in shares) | shares 171.0