    <SEC-DOCUMENT>0000776867-25-000010-index.html : 20250707
    <SEC-HEADER>0000776867-25-000010.hdr.sgml : 20250707
    <ACCEPTANCE-DATETIME>20250707160602
    ACCESSION NUMBER:		0000776867-25-000010
    CONFORMED SUBMISSION TYPE:	11-K
    PUBLIC DOCUMENT COUNT:		4
    CONFORMED PERIOD OF REPORT:	20241231
    FILED AS OF DATE:		20250707
    DATE AS OF CHANGE:		20250707

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			WHITE MOUNTAINS INSURANCE GROUP LTD
    		CENTRAL INDEX KEY:			0000776867
    		STANDARD INDUSTRIAL CLASSIFICATION:	FIRE, MARINE & CASUALTY INSURANCE [6331]
    		ORGANIZATION NAME:           	02 Finance
    		EIN:				942708455
    		STATE OF INCORPORATION:			D0
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		11-K
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-08993
    		FILM NUMBER:		251108030

    	BUSINESS ADDRESS:
    		STREET 1:		23 SOUTH MAIN STREET
    		STREET 2:		SUITE 3B
    		CITY:			HANOVER
    		STATE:			NH
    		ZIP:			03755
    		BUSINESS PHONE:		603 640 2200

    	MAIL ADDRESS:
    		STREET 1:		23 SOUTH MAIN STREET
    		STREET 2:		SUITE 3B
    		CITY:			HANOVER
    		STATE:			NH
    		ZIP:			03755

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	WHITE MOUNTAINS INSURANCE GROUP INC
    		DATE OF NAME CHANGE:	19990603

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	FUND AMERICAN ENTERPRISES HOLDINGS INC
    		DATE OF NAME CHANGE:	19920703

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	FUND AMERICAN COMPANIES INC
    		DATE OF NAME CHANGE:	19920701
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>11-K
    <SEQUENCE>1
    <FILENAME>wtm11-kjuly2025.htm
    <DESCRIPTION>11-K
    <TEXT>
    Document 1 - file: wtm11-kjuly2025.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>2
    <FILENAME>image1a.jpg
    <TEXT>
    Document 2 - file: image1a.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>3
    <FILENAME>image2a.jpg
    <TEXT>
    Document 3 - file: image2a.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>4
    <FILENAME>imagea.jpg
    <TEXT>
    Document 4 - file: imagea.jpg

    </DOCUMENT>
    </SEC-DOCUMENT>