Financial Instruments - Fair Values on Recurring Basis (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Debt Securities, Available-for-sale
Fixed income securities	$ 23,700		$ 23,700
Equity Securities, FV-NI, Gain (Loss)
Equity securities, unrealized gain (loss)	153	$ (145)	341	$ (1,800)
Recurring
Schedule of Investments [Line Items]
Cash	15,977		15,977		$ 17,055
Debt Securities, Available-for-sale
Gross unrealized gains	64		64
Gross unrealized losses	(44)		(44)
Cash, Cash Equivalents, and Marketable Securities
Cash, cash equivalents and marketable securities	97,739		97,739		104,735
Cash, cash equivalents and marketable securities, amortized cost	94,499		94,499
Less: Restricted cash, cash equivalents, and marketable securities	(3,542)		(3,542)		(3,533)
Total cash, cash equivalents, and marketable securities	94,197		94,197		101,202
Recurring | Level 1 securities
Schedule of Investments [Line Items]
Equity securities	3,220		3,220		3,318
Recurring | Level 1 securities | Money market funds
Schedule of Investments [Line Items]
Money market funds	32,317		32,317		28,282
Recurring | Level 1 securities | Money market funds | Money market funds
Schedule of Investments [Line Items]
Money market funds	32,317		32,317
Recurring | Level 2 securities | Foreign government and agency securities
Debt Securities, Available-for-sale
Fixed income securities, amortized cost	74		74
Gross unrealized gains	0		0
Gross unrealized losses	0		0
Fixed income securities	74		74		177
Recurring | Level 2 securities | U.S. government and agency securities
Debt Securities, Available-for-sale
Fixed income securities, amortized cost	5,400		5,400
Gross unrealized gains	7		7
Gross unrealized losses	(23)		(23)
Fixed income securities	5,384		5,384		3,401
Recurring | Level 2 securities | Corporate debt securities
Debt Securities, Available-for-sale
Fixed income securities, amortized cost	38,810		38,810
Gross unrealized gains	49		49
Gross unrealized losses	(11)		(11)
Fixed income securities	38,848		38,848		50,912
Recurring | Level 2 securities | Asset-backed securities
Debt Securities, Available-for-sale
Fixed income securities, amortized cost	1,893		1,893
Gross unrealized gains	8		8
Gross unrealized losses	(10)		(10)
Fixed income securities	1,891		1,891		1,523
Recurring | Level 2 securities | Other debt securities
Debt Securities, Available-for-sale
Fixed income securities, amortized cost	28		28
Gross unrealized gains	0		0
Gross unrealized losses	0		0
Fixed income securities	$ 28		$ 28		$ 67