SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT - Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Assets
Total assets	$ 7,000.7	$ 4,831.4
Liabilities
Total liabilities	3,296.0	1,013.5
Total White Mountains’s common shareholders’ equity	3,548.1	3,906.0
Non-controlling interests	156.6	(88.1)
Total liabilities and equity	7,000.7	4,831.4
White Mountains Insurance Group Ltd.
Assets
Cash	0.6	0.7
Fixed maturity investments, at fair value	0.0	10.1
Short-term investments, at amortized cost	6.7	24.3
Other assets	3.0	2.5
Investments in consolidated subsidiaries	3,661.8	3,726.0
Total assets	3,672.1	3,763.6
Liabilities
Payable to subsidiary	104.9	(195.6)
Other liabilities	10.1	39.7
Total liabilities	115.0	(155.9)
Total White Mountains’s common shareholders’ equity	3,548.1	3,906.0
Non-controlling interests	9.0	13.5
Total liabilities and equity	$ 3,672.1	3,763.6
Sirius Group | Swedish Tax Authority | Sirius Group
Liabilities
Loss contingency accrual		$ 18.7