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
6 Months Ended
Jun. 30, 2021
USD ($)
position
Dec. 31, 2020
USD ($)
Schedule Of Investments And Restricted Deposits By Type [Line Items]    
Accrued interest income | $ $ 92 $ 86
Positions from which gross unrealized losses were generated 1,512  
Total unrealized investment positions 6,515  
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 97.00%