Fair Value Measurements - Schedule of Fair Value Measurements by Level for Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Assets
Cash and cash equivalents	$ 14,815	$ 14,063
Investments:
Equity securities	13	14
Total assets at fair value	35,895	34,457
U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	572	591
Corporate securities
Investments:
Fair value	11,157	10,507
Municipal securities
Investments:
Fair value	4,076	4,030
Short-term time deposits
Investments:
Fair value	193	425
Asset-backed securities
Investments:
Fair value	1,958	1,812
Residential mortgage-backed securities
Investments:
Fair value	1,749	1,679
Commercial mortgage-backed securities
Investments:
Fair value	1,286	1,239
Level I
Assets
Cash and cash equivalents	14,815	14,063
Investments:
Total assets at fair value	15,471	14,760
Level II
Assets
Cash and cash equivalents	0	0
Investments:
Total assets at fair value	20,424	19,697
Level III
Assets
Cash and cash equivalents	0	0
Investments:
Total assets at fair value	0	0
Investments:
Investments:
Fair value	19,658	18,990
Total investments	19,671	19,004
Investments: \| U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	66	58
Investments: \| Corporate securities
Investments:
Fair value	11,155	10,505
Investments: \| Municipal securities
Investments:
Fair value	3,251	3,272
Investments: \| Short-term time deposits
Investments:
Fair value	193	425
Investments: \| Asset-backed securities
Investments:
Fair value	1,958	1,812
Investments: \| Residential mortgage-backed securities
Investments:
Fair value	1,749	1,679
Investments: \| Commercial mortgage-backed securities
Investments:
Fair value	1,286	1,239
Investments: \| Equity securities
Investments:
Equity securities	13	14
Investments: \| Level I
Investments:
Total investments	78	71
Investments: \| Level I \| U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	66	58
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	12	13
Investments: \| Level II
Investments:
Total investments	19,593	18,933
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	11,155	10,505
Investments: \| Level II \| Municipal securities
Investments:
Fair value	3,251	3,272
Investments: \| Level II \| Short-term time deposits
Investments:
Fair value	193	425
Investments: \| Level II \| Asset-backed securities
Investments:
Fair value	1,958	1,812
Investments: \| Level II \| Residential mortgage-backed securities
Investments:
Fair value	1,749	1,679
Investments: \| Level II \| Commercial mortgage-backed securities
Investments:
Fair value	1,286	1,239
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	1,409	1,390
Restricted deposits: \| U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	506	533
Restricted deposits: \| Corporate securities
Investments:
Fair value	2	2
Restricted deposits: \| Municipal securities
Investments:
Fair value	825	758
Restricted deposits: \| Cash and cash equivalents
Investments:
Fair value	72	93
Restricted deposits: \| Certificates of deposit
Investments:
Fair value	4	4
Restricted deposits: \| Level I
Investments:
Fair value	578	626
Restricted deposits: \| Level I \| U.S. Treasury securities and obligations of U.S. government corporations and agencies
Investments:
Fair value	506	533
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	72	93
Restricted deposits: \| Level I \| Certificates of deposit
Investments:
Fair value	0	0
Restricted deposits: \| Level II
Investments:
Fair value	831	764
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	2	2
Restricted deposits: \| Level II \| Municipal securities
Investments:
Fair value	825	758
Restricted deposits: \| Level II \| Cash and cash equivalents
Investments:
Fair value	0	0
Restricted deposits: \| Level II \| Certificates of deposit
Investments:
Fair value	4	4
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.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
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-Section 50
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-Publisher FASB
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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.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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-Section 50
-Paragraph 2
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

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- Definition

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).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
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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.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
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-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

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