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Subsequent Event Subsequent Event | 3 Months Ended
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Mar. 31, 2017
Subsequent Event [Line Items] |
Subsequent Events [Text Block] | Note 20. Subsequent Event On May 2, 2017, OneBeacon announced it had entered into a definitive agreement to be acquired by Intact Financial Corporation in an all-cash transaction for $18.10 per share, or roughly 1.65 x tangible book value (the “Transaction”). In addition, White Mountains entered into a definitive agreement to vote its shares of OneBeacon Ltd. in favor of the “Transaction”. White Mountains owns 75.7% of OneBeacon’s outstanding common shares, representing 96.9% of the voting power. White Mountains expects to receive gross proceeds of $1.3 billion from the Transaction, which is expected to close in the fourth quarter of 2017. It is subject to regulatory approval and other customary closing conditions.

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- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
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- Definition The entire disclosure for significant events or transactions that occurred after the balance sheet date through the date the financial statements were issued or the date the financial statements were available to be issued. Examples include: the sale of a capital stock issue, purchase of a business, settlement of litigation, catastrophic loss, significant foreign exchange rate changes, loans to insiders or affiliates, and transactions not in the ordinary course of business. + References No definition available. + Details
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