ACQUISITIONS AND DISPOSITIONS (Details) shares in Millions, $ in Millions		1 Months Ended	3 Months Ended
	Apr. 01, 2021 USD ($) shares	Dec. 31, 2019 USD ($)	Mar. 31, 2021 USD ($) vacation_ownership_unit	Mar. 31, 2020 USD ($) vacation_ownership_unit
Business Acquisition
Purchase of vacation ownership units			$ 99	$ 61
Welk Hospitality Group, Inc.
Business Acquisition
Restricted cash			$ 152
Welk Hospitality Group, Inc. | Subsequent event
Business Acquisition
Business Acquisition, value assigned	$ 485
Welk Hospitality Group, Inc. | Common Stock | Subsequent event
Business Acquisition
Business acquisition, number of shares | shares	1.4
New York City, New York
Business Acquisition
Number of vacation ownership units acquired | vacation_ownership_unit			120	57
Asset acquisition, consideration transferred			$ 98	$ 89
Asset acquisition, recognized identifiable assets acquired, property and equipment				67
Purchase of vacation ownership units		$ 20		22
Asset acquisition, recognized identifiable assets acquired, other assets				$ 22
San Francisco, California
Business Acquisition
Number of vacation ownership units acquired | vacation_ownership_unit			44	34
Asset acquisition, consideration transferred			$ 34	$ 26
Asset acquisition, recognized identifiable assets acquired, inventory			29	18
Asset acquisition, recognized identifiable assets acquired, property and equipment				3
Purchase of vacation ownership units				5
Asset acquisition, recognized identifiable assets acquired, other assets			$ 5	$ 5
Costa Rica
Business Acquisition
Number of vacation ownership units acquired | vacation_ownership_unit				24
Asset acquisition, consideration transferred				$ 14
Asset acquisition, recognized identifiable assets acquired, inventory				13
Asset acquisition, recognized identifiable assets acquired, property and equipment				$ 1