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INVESTMENTS - Schedule of Financial Instruments by Significant Categories and Fair Value Measurement on a Recurring Basis (Details) - Fair Value Measurement on a Recurring Basis - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Debt Securities |  |
Cash equivalents: | $ 179 | $ 571
Amortized Cost | 206 | 230
Gross Unrealized Gains | 2 | 0
Gross Unrealized Losses | 0 | (3)
Fair Value | 208 | 227
Cash and Cash Equivalents |  |
Debt Securities |  |
Cash equivalents: | 86 | 257
Fair Value | 0 | 0
Investments |  |
Debt Securities |  |
Cash equivalents: | 0 | 0
Fair Value | 0 | 0
Restricted Cash, Cash Equivalents and Investments |  |
Debt Securities |  |
Cash equivalents: | 93 | 314
Fair Value | 208 | 227
Level 2 | Corporate bonds |  |
Debt Securities |  |
Amortized Cost | 34 | 35
Gross Unrealized Gains | 0 |
Gross Unrealized Losses | 0 | 0
Fair Value | 34 | 35
Level 2 | Agency securities |  |
Debt Securities |  |
Amortized Cost | 11 | 18
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | (1)
Fair Value | 11 | 17
Level 2 | U.S. treasuries |  |
Debt Securities |  |
Amortized Cost | 161 | 176
Gross Unrealized Gains | 2 |
Gross Unrealized Losses | 0 | (2)
Fair Value | 163 | 174
Level 2 | Certificate of deposit |  |
Debt Securities |  |
Amortized Cost |  | 1
Gross Unrealized Gains |  | 0
Gross Unrealized Losses |  | 0
Fair Value |  | 1
Level 2 | Cash and Cash Equivalents | Corporate bonds |  |
Debt Securities |  |
Fair Value | 0 | 0
Level 2 | Cash and Cash Equivalents | Agency securities |  |
Debt Securities |  |
Fair Value | 0 | 0
Level 2 | Cash and Cash Equivalents | U.S. treasuries |  |
Debt Securities |  |
Fair Value | 0 | 0
Level 2 | Cash and Cash Equivalents | Certificate of deposit |  |
Debt Securities |  |
Fair Value |  | 0
Level 2 | Investments | Corporate bonds |  |
Debt Securities |  |
Fair Value | 0 |
Level 2 | Investments | Agency securities |  |
Debt Securities |  |
Fair Value | 0 |
Level 2 | Investments | U.S. treasuries |  |
Debt Securities |  |
Fair Value | 0 |
Level 2 | Investments | Certificate of deposit |  |
Debt Securities |  |
Fair Value |  | 0
Level 2 | Restricted Cash, Cash Equivalents and Investments | Corporate bonds |  |
Debt Securities |  |
Fair Value | 34 | 35
Level 2 | Restricted Cash, Cash Equivalents and Investments | Agency securities |  |
Debt Securities |  |
Fair Value | 11 | 17
Level 2 | Restricted Cash, Cash Equivalents and Investments | U.S. treasuries |  |
Debt Securities |  |
Fair Value | 163 | 174
Level 2 | Restricted Cash, Cash Equivalents and Investments | Certificate of deposit |  |
Debt Securities |  |
Fair Value |  | 1
Money market mutual funds | Level 1 |  |
Debt Securities |  |
Cash equivalents: | 172 | 570
Money market mutual funds | Level 1 | Cash and Cash Equivalents |  |
Debt Securities |  |
Cash equivalents: | 86 | 257
Money market mutual funds | Level 1 | Investments |  |
Debt Securities |  |
Cash equivalents: | 0 | 0
Money market mutual funds | Level 1 | Restricted Cash, Cash Equivalents and Investments |  |
Debt Securities |  |
Cash equivalents: | 86 | 313
U.S. treasuries | Level 2 |  |
Debt Securities |  |
Cash equivalents: | 7 | 1
U.S. treasuries | Level 2 | Cash and Cash Equivalents |  |
Debt Securities |  |
Cash equivalents: | 0 | 0
U.S. treasuries | Level 2 | Investments |  |
Debt Securities |  |
Cash equivalents: | 0 | 0
U.S. treasuries | Level 2 | Restricted Cash, Cash Equivalents and Investments |  |
Debt Securities |  |
Cash equivalents: | $ 7 | $ 1

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- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-2 + Details
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