Annual report pursuant to Section 13 and 15(d)

Short-term and Long-term Investments, Restricted Deposits - Fair Value of Available-for-Sale Investments in a Continuous Unrealized Loss Position (Details)

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Short-term and Long-term Investments, Restricted Deposits - Fair Value of Available-for-Sale Investments in a Continuous Unrealized Loss Position (Details) - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Unrealized Losses    
Less Than 12 Months $ (5) $ (36)
12 Months or More (4) (55)
Fair Value    
Less Than 12 Months 703 2,555
12 Months or More 343 2,420
U.S. Treasury securities and obligations of U.S. government corporations and agencies    
Unrealized Losses    
Less Than 12 Months 0 0
12 Months or More 0 (2)
Fair Value    
Less Than 12 Months 11 59
12 Months or More 31 202
Corporate securities    
Unrealized Losses    
Less Than 12 Months (2) (27)
12 Months or More (2) (25)
Fair Value    
Less Than 12 Months 192 1,389
12 Months or More 48 871
Municipal securities    
Unrealized Losses    
Less Than 12 Months (1) (4)
12 Months or More 0 (14)
Fair Value    
Less Than 12 Months 185 591
12 Months or More 11 806
Asset-backed securities    
Unrealized Losses    
Less Than 12 Months (1) (2)
12 Months or More (1) (2)
Fair Value    
Less Than 12 Months 153 318
12 Months or More 151 168
Residential mortgage-backed securities    
Unrealized Losses    
Less Than 12 Months 0 (1)
12 Months or More (1) (8)
Fair Value    
Less Than 12 Months 44 61
12 Months or More 81 233
Commercial mortgage- backed securities    
Unrealized Losses    
Less Than 12 Months (1) (2)
12 Months or More 0 (4)
Fair Value    
Less Than 12 Months 118 137
12 Months or More $ 21 $ 140