Investments - Total Investment Schedule (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Total Investments [Line Items]
Current	$ 3,006	$ 3,000
Long-term	22,136	20,812
Total	25,142	23,812
Debt securities available for sale
Total Investments [Line Items]
Current	2,878	2,774
Long-term	19,468	18,414
Total	22,346	21,188
Mortgage loans
Total Investments [Line Items]
Current	128	226
Long-term	848	821
Total	976	1,047
Other investments
Total Investments [Line Items]
Current	0	0
Long-term	1,820	1,577
Total	$ 1,820	$ 1,577