v3.8.0.1
Health Net - Narrative (Details)
$ / shares in Units, shares in Thousands, $ in Millions
12 Months Ended
Mar. 24, 2016
USD ($)
$ / shares
shares
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Business Acquisition [Line Items]        
Centene share price (in dollars per share) | $ / shares $ 62.70      
Health Net, Inc.        
Business Acquisition [Line Items]        
Consideration transferred, including assumed debt $ 5,990      
Assumption of outstanding debt 703      
Total consideration for acquisition transaction 5,287      
Consideration transferred, common stock issued, value 3,038      
Cash paid 2,247      
Fair value adjustment, stock based compensation $ 2      
Shares converted ratio 0.622      
Acquisition share price (in usd per share) | $ / shares $ 28.25      
Common stock issued for acquisition (in shares) | shares 48,449      
Health Net, Inc. | Selling, General and Administrative Expenses        
Business Acquisition [Line Items]        
Acquisition related expenses   $ 7 $ 234 $ 27