Investments - Estimated fair values of short and long-term investments classified by date of contractual maturity (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
One year or less (including restricted cash of $41)	$ 1,821
One year through two years (including restricted cash of $5)	639
Two years through three years	307
Three years through four years	130
Estimated Fair Value	2,897
Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Restricted cash included in long-term investments	1,831	$ 2,532
Estimated Fair Value	1,821	2,521
Short-term investments: | Restricted cash
Debt Securities, Available-for-sale [Line Items]
Restricted cash included in long-term investments	41	36
Estimated Fair Value	41	36
Long-term investments:
Debt Securities, Available-for-sale [Line Items]
Restricted cash included in long-term investments	1,145	1,303
Estimated Fair Value	1,076	1,216
Long-term investments: | Restricted cash
Debt Securities, Available-for-sale [Line Items]
Restricted cash included in long-term investments	5	13
Estimated Fair Value	$ 5	$ 13