Investments (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Total Investments [Line Items]
Current investments	$ 2,831	$ 2,373
Long-term investments	20,216	17,314
Total investments	23,047	19,687
Debt securities available for sale
Total Investments [Line Items]
Current investments	2,578	2,251
Long-term investments	17,820	14,671
Total investments	20,398	16,922
Mortgage loans
Total Investments [Line Items]
Current investments	253	122
Long-term investments	871	1,091
Total investments	1,124	1,213
Other investments
Total Investments [Line Items]
Current investments	0	0
Long-term investments	1,525	1,552
Total investments	$ 1,525	$ 1,552