Quarterly report pursuant to Section 13 or 15(d)

Short-term and Long-term Investments, Restricted Deposits - Narrative (Details)

v3.21.2
Short-term and Long-term Investments, Restricted Deposits - Narrative (Details)
$ in Millions
1 Months Ended 3 Months Ended 9 Months Ended
Sep. 30, 2021
USD ($)
position
Jul. 31, 2021
USD ($)
Sep. 30, 2021
USD ($)
position
Sep. 30, 2021
USD ($)
position
Sep. 30, 2020
USD ($)
Dec. 31, 2020
USD ($)
Jun. 30, 2019
Schedule Of Investments And Restricted Deposits By Type [Line Items]              
Accrued interest income $ 92   $ 92 $ 92   $ 86  
Positions from which gross unrealized losses were generated | position 1,887   1,887 1,887      
Total unrealized investment positions | position 6,468   6,468 6,468      
Step acquisition, gain on investment       $ 309 $ 0    
Circle Health              
Schedule Of Investments And Restricted Deposits By Type [Line Items]              
Acquisition, interests acquired   60.00%          
Business combination, ownership percentage   100.00%          
Circle Health              
Schedule Of Investments And Restricted Deposits By Type [Line Items]              
Equity method investment, ownership percentage             40.00%
Cash paid   $ 705          
Step acquisition, gain on investment     $ 309        
RxAdvance              
Schedule Of Investments And Restricted Deposits By Type [Line Items]              
Impairment of equity method investment $ 229            
Commercial mortgage-backed securities              
Schedule Of Investments And Restricted Deposits By Type [Line Items]              
Investments recorded at fair value that carry rating of AA Plus, weighted average (in years)       4 years      
Rated Securities | External Credit Rating, Investment Grade | Investment Securities              
Schedule Of Investments And Restricted Deposits By Type [Line Items]              
Percentage of investments in rated securities carry an investment grade rating by nationally recognized statistical rating organizations       98.00%