Quarterly report pursuant to Section 13 or 15(d)

Segment Information (Details)

v3.8.0.1
Segment Information (Details)
$ in Millions
3 Months Ended
Mar. 31, 2018
USD ($)
segment
Mar. 31, 2017
USD ($)
Segment Reporting [Abstract]    
Number of operating segments | segment 2  
Segment Reporting Information [Line Items]    
Total revenues $ 13,194 $ 11,724
Earnings from operations 540 240
Eliminations    
Segment Reporting Information [Line Items]    
Total revenues (2,256) (2,344)
Managed Care    
Segment Reporting Information [Line Items]    
Total revenues 12,449 11,115
Earnings from operations 470 187
Managed Care | Operating Segments    
Segment Reporting Information [Line Items]    
Total revenues 12,474 11,126
Managed Care | Eliminations    
Segment Reporting Information [Line Items]    
Total revenues 25 11
Specialty Services    
Segment Reporting Information [Line Items]    
Total revenues 745 609
Earnings from operations 70 53
Specialty Services | Operating Segments    
Segment Reporting Information [Line Items]    
Total revenues 2,976 2,942
Specialty Services | Eliminations    
Segment Reporting Information [Line Items]    
Total revenues $ 2,231 $ 2,333