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