v3.26.1
Document And Entity Information
May 12, 2026
Document Information [Line Items]  
Entity Registrant Name HANOVER INSURANCE GROUP, INC.
Document Type 8-K
Amendment Flag false
Entity Central Index Key 0000944695
Document Period End Date May 12, 2026
Entity Emerging Growth Company false
Entity File Number 1-13754
Entity Incorporation State Country Code DE
Entity Tax Identification Number 04-3263626
Entity Address, Address Line One 440 Lincoln Street
Entity Address, City or Town Worcester
Entity Address, State or Province MA
Entity Address, Postal Zip Code 01653
City Area Code (508)
Local Phone Number 855-1000
Written Communications false
Soliciting Material false
Pre Commencement Tender Offer false
Pre Commencement Issuer Tender Offer false
Security 12b Title Common Stock, $.01 par value
Trading Symbol THG
Security Exchange Name NYSE