Wyndham Hotels & Resorts, Inc. Quarterly report pursuant to Section 13 or 15(d)

New Accounting Pronouncements (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total cash, cash equivalents and restricted cash	$ 73	$ 59	$ 34	$ 30
Cash and cash equivalents	71	57
Other current assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted cash	$ 2	2
Accounting Standards Update 2014-09 \| New Revenue Standard Adjustment \| Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting standard					$ (29)
Accounting Standards Update 2016-16 \| Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting standard		$ 15