ACQUISITIONS AND DISPOSITIONS (Details) shares in Millions		1 Months Ended	3 Months Ended				9 Months Ended
	Apr. 01, 2021 USD ($) shares	Dec. 31, 2019 USD ($)	Sep. 30, 2021 USD ($)	Mar. 31, 2021 USD ($) vacation_ownership_unit	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($) vacation_ownership_unit	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Business Acquisition [Line Items]
Purchase of vacation ownership units							$ 99,000,000	$ 61,000,000
Losses and other expense, net			$ 31,000,000		$ 0		27,000,000	42,000,000
Note receivable (less than)					1,000,000			1,000,000
Dispositions, net							0	15,000,000
Land
Business Acquisition [Line Items]
Losses and other expense, net					6,000,000			6,000,000
Dispositions, net					15,000,000
Joint Venture
Business Acquisition [Line Items]
Losses and other expense, net					$ (5,000,000)		(1,000,000)	(5,000,000)
Welk
Business Acquisition [Line Items]
Business acquisition, value assigned	$ 405,000,000
Business acquisition, number of shares (in shares) | shares	1.4
Business combinations, pro forma, acquisition-related costs							$ 0	$ 18,000,000
Welk | Common Stock
Business Acquisition [Line Items]
Business acquisition, number of shares (in shares) | shares	1.4
Costa Rica
Business Acquisition [Line Items]
Number of vacation ownership units acquired | vacation_ownership_unit				24
Asset acquisition, consideration transferred				$ 14,000,000
Asset acquisition, recognized identifiable assets acquired, inventory				13,000,000
Asset acquisition, recognized identifiable assets acquired, property and equipment				$ 1,000,000
New York City, New York
Business Acquisition [Line Items]
Number of vacation ownership units acquired | vacation_ownership_unit				120		57
Asset acquisition, consideration transferred				$ 98,000,000		$ 89,000,000
Asset acquisition, recognized identifiable assets acquired, property and equipment						67,000,000
Purchase of vacation ownership units		$ 20,000,000				22,000,000
Asset acquisition, recognized identifiable assets acquired, other assets						$ 22,000,000
San Francisco, California
Business Acquisition [Line Items]
Number of vacation ownership units acquired | vacation_ownership_unit				44		34
Asset acquisition, consideration transferred				$ 34,000,000		$ 26,000,000
Asset acquisition, recognized identifiable assets acquired, inventory				29,000,000		18,000,000
Asset acquisition, recognized identifiable assets acquired, property and equipment						3,000,000
Purchase of vacation ownership units						5,000,000
Asset acquisition, recognized identifiable assets acquired, other assets				$ 5,000,000		$ 5,000,000