Investments - Estimated fair values of short and long-term investments classified as available for sale by date of contractual maturity (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
One year or less (including restricted cash of $36)	$ 2,521
One year through two years (including restricted cash of $13)	730
Two years through three years	357
Three years through four years	113
Four years through five years	16
Thereafter	0
Estimated Fair Value	3,737
Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	2,521	$ 4,199
Restricted cash included in long-term investments	2,532	4,198
Short-term investments: | Restricted cash
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	36	22
Restricted cash included in long-term investments	36	22
Long-term investments:
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,216	1,727
Restricted cash included in long-term investments	1,303	1,733
Long-term investments: | Restricted cash
Debt Securities, Available-for-sale [Line Items]
Restricted cash included in long-term investments	$ 13	$ 0