    <SEC-DOCUMENT>0000776867-21-000022-index.html : 20211202
    <SEC-HEADER>0000776867-21-000022.hdr.sgml : 20211202
    <ACCEPTANCE-DATETIME>20211202162251
    ACCESSION NUMBER:		0000776867-21-000022
    CONFORMED SUBMISSION TYPE:	8-K
    PUBLIC DOCUMENT COUNT:		23
    CONFORMED PERIOD OF REPORT:	20211129
    ITEM INFORMATION:		Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers
    ITEM INFORMATION:		Financial Statements and Exhibits
    FILED AS OF DATE:		20211202
    DATE AS OF CHANGE:		20211202

    FILER:

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

    	FILING VALUES:
    		FORM TYPE:		8-K
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-08993
    		FILM NUMBER:		211466867

    	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>8-K
    <SEQUENCE>1
    <FILENAME>wtm-20211129.htm
    <DESCRIPTION>8-K
    <TEXT>
    Document 1 - file: wtm-20211129.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-10.1
    <SEQUENCE>2
    <FILENAME>wtm11292021exhibit101.htm
    <DESCRIPTION>EX-10.1
    <TEXT>
    Document 2 - file: wtm11292021exhibit101.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-10.2
    <SEQUENCE>3
    <FILENAME>wtm11292021exhibit102.htm
    <DESCRIPTION>EX-10.2
    <TEXT>
    Document 3 - file: wtm11292021exhibit102.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.1
    <SEQUENCE>4
    <FILENAME>wtm11292021exhibit991.htm
    <DESCRIPTION>EX-99.1
    <TEXT>
    Document 4 - file: wtm11292021exhibit991.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.SCH
    <SEQUENCE>5
    <FILENAME>wtm-20211129.xsd
    <DESCRIPTION>XBRL TAXONOMY EXTENSION SCHEMA DOCUMENT
    <TEXT>
    Document 5 - file: wtm-20211129.xsd

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.LAB
    <SEQUENCE>6
    <FILENAME>wtm-20211129_lab.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION LABEL LINKBASE DOCUMENT
    <TEXT>
    Document 6 - file: wtm-20211129_lab.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.PRE
    <SEQUENCE>7
    <FILENAME>wtm-20211129_pre.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE DOCUMENT
    <TEXT>
    Document 7 - file: wtm-20211129_pre.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>8
    <FILENAME>image1.jpg
    <TEXT>
    Document 8 - file: image1.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>9
    <FILENAME>wtm11292021exhibit101001.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 9 - file: wtm11292021exhibit101001.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>10
    <FILENAME>wtm11292021exhibit101002.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 10 - file: wtm11292021exhibit101002.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>11
    <FILENAME>wtm11292021exhibit102001.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 11 - file: wtm11292021exhibit102001.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>12
    <FILENAME>wtm11292021exhibit102002.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 12 - file: wtm11292021exhibit102002.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>13
    <FILENAME>wtm11292021exhibit102003.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 13 - file: wtm11292021exhibit102003.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>14
    <FILENAME>wtm11292021exhibit102004.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 14 - file: wtm11292021exhibit102004.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>15
    <FILENAME>wtm11292021exhibit102005.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 15 - file: wtm11292021exhibit102005.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>16
    <FILENAME>wtm-20211129_htm.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 16 - file: wtm-20211129_htm.html

    Document 16 - RAW XML: wtm-20211129_htm.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>17
    <FILENAME>R1.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 17 - file: R1.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EXCEL
    <SEQUENCE>18
    <FILENAME>Financial_Report.xlsx
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 18 - file: Financial_Report.xlsx

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>19
    <FILENAME>Show.js
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 19 - file: Show.js

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>20
    <FILENAME>report.css
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 20 - file: report.css

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>21
    <FILENAME>FilingSummary.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 21 - file: FilingSummary.html

    Document 21 - RAW XML: FilingSummary.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>JSON
    <SEQUENCE>24
    <FILENAME>MetaLinks.json
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 24 - file: MetaLinks.json

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>ZIP
    <SEQUENCE>25
    <FILENAME>0000776867-21-000022-xbrl.zip
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 25 - file: 0000776867-21-000022-xbrl.zip

    </DOCUMENT>
    </SEC-DOCUMENT>