Fair Value Measurements - Schedule of Fair Value Measurements by Level for Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Assets
Cash and cash equivalents	$ 20,700	$ 17,888
Investments:
Equity securities	1	1
Total assets at fair value	38,620	37,635
U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	559	535
Corporate securities
Investments:
Fair value	10,180	10,662
Municipal securities
Investments:
Fair value	3,059	3,758
Short-term time deposits
Investments:
Fair value	72	205
Asset-backed securities
Investments:
Fair value	1,365	1,666
Residential mortgage-backed securities
Investments:
Fair value	1,499	1,714
Commercial mortgage-backed securities
Investments:
Fair value	997	1,136
Level I
Assets
Cash and cash equivalents	20,700	17,888
Investments:
Total assets at fair value	21,446	18,492
Level II
Assets
Cash and cash equivalents	0	0
Investments:
Total assets at fair value	17,174	19,143
Level III
Assets
Cash and cash equivalents	0	0
Investments:
Total assets at fair value	0	0
Investments:
Investments:
Fair value	16,449	18,334
Total investments	16,450	18,335
Investments: \| U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	53	55
Investments: \| Corporate securities
Investments:
Fair value	10,141	10,652
Investments: \| Municipal securities
Investments:
Fair value	2,322	2,906
Investments: \| Short-term time deposits
Investments:
Fair value	72	205
Investments: \| Asset-backed securities
Investments:
Fair value	1,365	1,666
Investments: \| Residential mortgage-backed securities
Investments:
Fair value	1,499	1,714
Investments: \| Commercial mortgage-backed securities
Investments:
Fair value	997	1,136
Investments: \| Equity securities
Investments:
Equity securities	1	1
Investments: \| Level I
Investments:
Total investments	53	55
Investments: \| Level I \| U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	53	55
Investments: \| Level I \| Corporate securities
Investments:
Fair value	0	0
Investments: \| Level I \| Municipal securities
Investments:
Fair value	0	0
Investments: \| Level I \| Short-term time deposits
Investments:
Fair value	0	0
Investments: \| Level I \| Asset-backed securities
Investments:
Fair value	0	0
Investments: \| Level I \| Residential mortgage-backed securities
Investments:
Fair value	0	0
Investments: \| Level I \| Commercial mortgage-backed securities
Investments:
Fair value	0	0
Investments: \| Level I \| Equity securities
Investments:
Equity securities	0	0
Investments: \| Level II
Investments:
Total investments	16,397	18,280
Investments: \| Level II \| U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	0	0
Investments: \| Level II \| Corporate securities
Investments:
Fair value	10,141	10,652
Investments: \| Level II \| Municipal securities
Investments:
Fair value	2,322	2,906
Investments: \| Level II \| Short-term time deposits
Investments:
Fair value	72	205
Investments: \| Level II \| Asset-backed securities
Investments:
Fair value	1,365	1,666
Investments: \| Level II \| Residential mortgage-backed securities
Investments:
Fair value	1,499	1,714
Investments: \| Level II \| Commercial mortgage-backed securities
Investments:
Fair value	997	1,136
Investments: \| Level II \| Equity securities
Investments:
Equity securities	1	1
Investments: \| Level III
Investments:
Total investments	0	0
Investments: \| Level III \| U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	0	0
Investments: \| Level III \| Corporate securities
Investments:
Fair value	0	0
Investments: \| Level III \| Municipal securities
Investments:
Fair value	0	0
Investments: \| Level III \| Short-term time deposits
Investments:
Fair value	0	0
Investments: \| Level III \| Asset-backed securities
Investments:
Fair value	0	0
Investments: \| Level III \| Residential mortgage-backed securities
Investments:
Fair value	0	0
Investments: \| Level III \| Commercial mortgage-backed securities
Investments:
Fair value	0	0
Investments: \| Level III \| Equity securities
Investments:
Equity securities	0	0
Restricted deposits:
Investments:
Fair value	1,470	1,412
Restricted deposits: \| U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	506	480
Restricted deposits: \| Corporate securities
Investments:
Fair value	39	10
Restricted deposits: \| Municipal securities
Investments:
Fair value	737	852
Restricted deposits: \| Cash and cash equivalents
Investments:
Fair value	187	69
Restricted deposits: \| Certificates of deposit
Investments:
Fair value	1	1
Restricted deposits: \| Level I
Investments:
Fair value	693	549
Restricted deposits: \| Level I \| U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	506	480
Restricted deposits: \| Level I \| Corporate securities
Investments:
Fair value	0	0
Restricted deposits: \| Level I \| Municipal securities
Investments:
Fair value	0	0
Restricted deposits: \| Level I \| Cash and cash equivalents
Investments:
Fair value	187	69
Restricted deposits: \| Level I \| Certificates of deposit
Investments:
Fair value	0	0
Restricted deposits: \| Level II
Investments:
Fair value	777	863
Restricted deposits: \| Level II \| U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	0	0
Restricted deposits: \| Level II \| Corporate securities
Investments:
Fair value	39	10
Restricted deposits: \| Level II \| Municipal securities
Investments:
Fair value	737	852
Restricted deposits: \| Level II \| Cash and cash equivalents
Investments:
Fair value	0	0
Restricted deposits: \| Level II \| Certificates of deposit
Investments:
Fair value	1	1
Restricted deposits: \| Level III
Investments:
Fair value	0	0
Restricted deposits: \| Level III \| U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	0	0
Restricted deposits: \| Level III \| Corporate securities
Investments:
Fair value	0	0
Restricted deposits: \| Level III \| Municipal securities
Investments:
Fair value	0	0
Restricted deposits: \| Level III \| Cash and cash equivalents
Investments:
Fair value	0	0
Restricted deposits: \| Level III \| Certificates of deposit
Investments:
Fair value	$ 0	$ 0

Fair value portion of asset recognized for present right to economic benefit.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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