SHARE-BASED COMPENSATION - Deferred Compensation Costs (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation costs related to unvested awards	$ 32	$ 31
Service-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation costs related to unvested awards	23	17
Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation costs related to unvested awards	6	10
ILG Acquisition Converted RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation costs related to unvested awards	1	3
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation costs related to unvested awards	30	30
SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation costs related to unvested awards	2	1
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation costs related to unvested awards	$ 0	$ 0