Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2022	Jul. 25, 2022
Cover [Abstract]
Amendment Flag	false
Document Type	10-Q
Document Period End Date	Jun. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Entity Registrant Name	WILLIS TOWERS WATSON PLC
Entity Central Index Key	0001140536
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		109,965,562
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Trading Symbol	WTW
Title of 12(b) Security	Ordinary Shares, nominal value $0.000304635 per share
Security Exchange Name	NASDAQ
Entity File Number	001-16503
Entity Incorporation, State or Country Code	L2
Entity Tax Identification Number	98-0352587
Entity Address, Address Line One	c/o Willis Group Limited
Entity Address, Address Line Two	51 Lime Street
Entity Address, City or Town	London
Entity Address, Country	GB
Entity Address, Postal Zip Code	EC3M 7DQ
City Area Code	011
Local Phone Number	44-20-3124-6000
Document Quarterly Report	true
Document Transition Report	false