SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)		12 Months Ended
		Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2017 USD ($)
Significant Accounting Policies [Line Items]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal, Statement of Income or Comprehensive Income [Extensible Enumeration]		Cost of revenues
Compensation costs from retirement savings plan		$ 240,000,000	$ 215,000,000	$ 137,000,000
Advertising costs		993,000,000	794,000,000	635,000,000
Allowance for credit losses		199,000,000	197,000,000
Goodwill impairment charge		0	0	0
Self-insurance reserve, current		198,000,000	172,000,000
Self-insurance reserve, noncurrent		$ 422,000,000	387,000,000
Measurement Input, Discount Rate | Valuation Technique, Discounted Cash Flow
Significant Accounting Policies [Line Items]
Self insurance review, measurement input		0.0425
Costs Incurred to Fulfill Contracts
Significant Accounting Policies [Line Items]
Capitalized costs		$ 419,000,000	402,000,000
Reimbursements
Significant Accounting Policies [Line Items]
Cost of revenues	[1]	18,799,000,000	17,424,000,000	15,141,000,000
Contract services, excluding loyalty program
Significant Accounting Policies [Line Items]
Increase (decrease) deferred revenue		76,000,000
Current and noncurrent deferred revenue		1,299,000,000	1,223,000,000
Deferred revenue recognized		222,000,000
Guest loyalty program
Significant Accounting Policies [Line Items]
Increase (decrease) deferred revenue		513,000,000
Current and noncurrent deferred revenue		7,519,000,000	7,006,000,000
Deferred revenue recognized		3,010,000,000
Current deferred revenue		3,487,000,000	3,328,000,000
Change in customer contract liability from change in estimates		72,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Avendra LLC
Significant Accounting Policies [Line Items]
Gain (loss) on disposal					$ 664,000,000
Gain (loss) on disposal, net of tax					$ 425,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Avendra LLC | Reimbursements
Significant Accounting Policies [Line Items]
Cost of revenues		$ 1,000,000	161,000,000	69,000,000
Cost of revenues, net of tax			$ 120,000,000	$ 52,000,000

[1] See Note 15 for disclosure of related party amounts.