SHARE-BASED COMPENSATION - Deferred Compensation Costs (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation costs related to unvested awards	$ 42	$ 39
Service-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation costs related to unvested awards	21	16
Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation costs related to unvested awards	14	7
ILG Acquisition Converted RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation costs related to unvested awards	5	15
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation costs related to unvested awards	40	38
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