Investments - Schedule of Total Investments (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Total Investments [Line Items]
Current	$ 3,000	$ 2,373
Long-term	20,812	17,314
Total	23,812	19,687
Debt securities available for sale
Total Investments [Line Items]
Current	2,774	2,251
Long-term	18,414	14,671
Total	21,188	16,922
Mortgage loans
Total Investments [Line Items]
Current	226	122
Long-term	821	1,091
Total	1,047	1,213
Other investments
Total Investments [Line Items]
Current	0	0
Long-term	1,577	1,552
Total	$ 1,577	$ 1,552