REVENUE - Timing of Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers	$ 2,619	$ 3,984	$ 2,785
Services transferred over time
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers	1,819	2,134	1,566
Goods or services transferred at a point in time
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers	800	1,850	1,219
Vacation Ownership
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers	2,265	3,490	2,621
Vacation Ownership | Services transferred over time
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers	1,616	1,896	1,467
Vacation Ownership | Goods or services transferred at a point in time
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers	649	1,594	1,154
Exchange & Third-Party Management
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers	307	450	160
Exchange & Third-Party Management | Services transferred over time
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers	156	194	95
Exchange & Third-Party Management | Goods or services transferred at a point in time
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers	151	256	65
Corporate and other
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers	47	44	4
Corporate and other | Services transferred over time
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers	47	44	4
Corporate and other | Goods or services transferred at a point in time
Revenue, Initial Application Period Cumulative Effect Transition
Revenue from contracts with customers	$ 0	$ 0	$ 0