Investments - Available-For-Sale Securities (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Investments
Estimated Fair Value	$ 4,382
Short-term investments:
Investments
Gross Amortized Cost	3,218	$ 2,552
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(15)	(19)
Estimated Fair Value	3,203	2,533
Short-term investments: | Corporate debt securities
Investments
Gross Amortized Cost	2,755	2,170
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(6)	(8)
Estimated Fair Value	2,749	2,162
Short-term investments: | Government and agency securities
Investments
Gross Amortized Cost	463	382
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(9)	(11)
Estimated Fair Value	454	371
Long-term investments:
Investments
Gross Amortized Cost	1,195	625
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(17)	(26)
Estimated Fair Value	1,179	599
Long-term investments: | Corporate debt securities
Investments
Gross Amortized Cost	774	338
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(5)	(10)
Estimated Fair Value	770	328
Long-term investments: | Government and agency securities
Investments
Gross Amortized Cost	421	287
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(12)	(16)
Estimated Fair Value	$ 409	$ 271