REVENUE - Revenue with Customers (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition
Cost reimbursements									$ 1,042	$ 1,108	$ 925
Revenue from contracts with customers									2,619	3,984	2,785
Financing									267	275	183
Revenues	$ 747	$ 649	$ 480	$ 1,010	$ 1,116	$ 1,066	$ 1,043	$ 1,034	2,886	4,259	2,968
Sale of vacation ownership products
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									546	1,354	990
Ancillary revenues
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									90	228	161
Management fee revenues
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									144	177	140
Exchange and other services revenues
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									521	544	198
Management and exchange
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									755	949	499
Rental
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									276	573	371
Corporate and other
Revenue, Initial Application Period Cumulative Effect Transition
Cost reimbursements									(141)	(119)	(28)
Revenue from contracts with customers									47	44	4
Financing									0	0	0
Revenues									47	44	4
Corporate and other | Sale of vacation ownership products
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									0	0	0
Corporate and other | Ancillary revenues
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									0	0	0
Corporate and other | Management fee revenues
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									(22)	(13)	(4)
Corporate and other | Exchange and other services revenues
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									210	176	35
Corporate and other | Management and exchange
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									188	163	31
Corporate and other | Rental
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									0	0	1
Vacation Ownership
Revenue, Initial Application Period Cumulative Effect Transition
Cost reimbursements									1,124	1,136	920
Revenue from contracts with customers									2,265	3,490	2,621
Financing									265	271	182
Revenues									2,530	3,761	2,803
Vacation Ownership | Sale of vacation ownership products
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									546	1,354	990
Vacation Ownership | Ancillary revenues
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									89	224	160
Vacation Ownership | Management fee revenues
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									149	144	114
Vacation Ownership | Exchange and other services revenues
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									118	120	85
Vacation Ownership | Management and exchange
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									356	488	359
Vacation Ownership | Rental
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									239	512	352
Exchange & Third-Party Management
Revenue, Initial Application Period Cumulative Effect Transition
Cost reimbursements									59	91	33
Revenue from contracts with customers									307	450	160
Financing									2	4	1
Revenues									309	454	161
Exchange & Third-Party Management | Sale of vacation ownership products
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									0	0	0
Exchange & Third-Party Management | Ancillary revenues
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									1	4	1
Exchange & Third-Party Management | Management fee revenues
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									17	46	30
Exchange & Third-Party Management | Exchange and other services revenues
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									193	248	78
Exchange & Third-Party Management | Management and exchange
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									211	298	109
Exchange & Third-Party Management | Rental
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers									$ 37	$ 61	$ 18