White Mountains Insurance Group, Ltd. conducts its business through insurance and reinsurance subsidiaries and affiliates. The Company operates in four segments include OneBeacon, Sirius Group, HG Global/BAM and Other Operations. The OneBeacon segment consists of OneBeacon Insurance Group, Ltd. (OneBeacon Ltd.), a company that owns a family of property and casualty insurance companies. The Sirius Group segment consists of Sirius International Insurance Group, Ltd., a company, and its subsidiaries (Sirius Group). The HG Global/BAM segment consists of White Mountains� investment in HG Global Ltd. (HG Global) and Build America Mutual Assurance Company (BAM). The Other Operations segment consists of the Company and its intermediate holding companies, its wholly owned investment management subsidiary, White Mountains Advisors LLC (WM Advisors).