Investments - Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale [Line Items]
Debt securities, AFS, continuous unrealized loss position, less than 12 months	$ 0	$ 134
Debt securities, AFS, continuous unrealized loss position, less than 12 months, accumulated loss	0	(1)
Debt securities, AFS, continuous unrealized loss position, 12 months or longer	45	127
Debt securities, AFS, continuous unrealized loss position, 12 months or longer, accumulated loss	(1)	(2)
Debt securities, AFS, unrealized loss position	45	261
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(1)	(3)
Commercial paper
Debt Securities, Available-for-Sale [Line Items]
Debt securities, AFS, continuous unrealized loss position, less than 12 months		84
Debt securities, AFS, continuous unrealized loss position, less than 12 months, accumulated loss		0
Debt securities, AFS, continuous unrealized loss position, 12 months or longer		0
Debt securities, AFS, continuous unrealized loss position, 12 months or longer, accumulated loss		0
Debt securities, AFS, unrealized loss position		84
Debt securities, available-for-sale, unrealized loss position, accumulated loss		0
U.S. government and government agency debt securities
Debt Securities, Available-for-Sale [Line Items]
Debt securities, AFS, continuous unrealized loss position, less than 12 months	0	48
Debt securities, AFS, continuous unrealized loss position, less than 12 months, accumulated loss	0	(1)
Debt securities, AFS, continuous unrealized loss position, 12 months or longer	43	118
Debt securities, AFS, continuous unrealized loss position, 12 months or longer, accumulated loss	(1)	(2)
Debt securities, AFS, unrealized loss position	43	166
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(1)	(3)
Corporate debt securities
Debt Securities, Available-for-Sale [Line Items]
Debt securities, AFS, continuous unrealized loss position, less than 12 months	0	2
Debt securities, AFS, continuous unrealized loss position, less than 12 months, accumulated loss	0	0
Debt securities, AFS, continuous unrealized loss position, 12 months or longer	2	9
Debt securities, AFS, continuous unrealized loss position, 12 months or longer, accumulated loss	0	0
Debt securities, AFS, unrealized loss position	2	11
Debt securities, available-for-sale, unrealized loss position, accumulated loss	$ 0	$ 0