SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)		12 Months Ended
		Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 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		$ 215,000,000	$ 137,000,000	$ 80,000,000
Advertising costs		794,000,000	635,000,000	470,000,000
Allowance for credit losses		197,000,000	191,000,000
Change in allowance for credit losses		29,000,000	27,000,000	22,000,000
Goodwill impairment charge		0	0	0
Self-insurance reserve, current		172,000,000	130,000,000
Self-insurance reserve, noncurrent		$ 387,000,000	287,000,000
Measurement Input, Discount Rate | Valuation Technique, Discounted Cash Flow
Significant Accounting Policies [Line Items]
Self insurance review, measurement input		0.0400
Costs Incurred to Fulfill Contracts
Significant Accounting Policies [Line Items]
Capitalized costs		$ 402,000,000	379,000,000
Reimbursements expenses
Significant Accounting Policies [Line Items]
Cost of revenues	[1]	17,424,000,000	15,141,000,000	10,322,000,000
Deferred revenue
Significant Accounting Policies [Line Items]
Increase (decrease) deferred revenue		(108,000,000)
Current and noncurrent deferred revenue		1,223,000,000	1,331,000,000
Deferred revenue recognized		274,000,000
Guest loyalty program
Significant Accounting Policies [Line Items]
Increase (decrease) deferred revenue		412,000,000
Current and noncurrent deferred revenue		7,006,000,000	6,594,000,000
Deferred revenue recognized		2,798,000,000
Reclassification from deferred revenue		112,000,000
Change in customer contract liability from change in estimates		148,000,000
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 expenses
Significant Accounting Policies [Line Items]
Cost of revenues		161,000,000	69,000,000	56,000,000
Cost of revenues, net of tax		$ 120,000,000	$ 52,000,000	$ 42,000,000

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