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Third Party Reinsurance | 3 Months Ended
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Mar. 31, 2017
Reinsurance Disclosures [Abstract] |
Third Party Reinsurance | Third Party Reinsurance In the normal course of business, White Mountains’s insurance subsidiaries may seek to limit losses that may arise from catastrophes or other events by reinsuring with third party reinsurers. White Mountains remains liable for risks reinsured in the event that the reinsurer does not honor its obligations under reinsurance contracts. OneBeacon At March 31, 2017, OneBeacon had $3.4 million and $174.7 million of reinsurance recoverables on paid and unpaid losses. At December 31, 2016, OneBeacon had $6.6 million and $172.9 million of reinsurance recoverables on paid and unpaid losses. Reinsurance contracts do not relieve OneBeacon of its obligation to its policyholders. OneBeacon is selective with its reinsurers, placing reinsurance with only those reinsurers having a strong financial condition. OneBeacon monitors the financial strength and ratings of its reinsurers on an ongoing basis. Uncollectible amounts related to the ongoing specialty business historically have not been significant. Effective May 1, 2017, OneBeacon renewed its property catastrophe reinsurance program through April 30, 2018. The program provides coverage for OneBeacon's property business as well as certain acts of terrorism. Under the program, the first $20.0 million of losses resulting from any single catastrophe are retained, with 100.0% of the next $110.0 million of losses resulting from the catastrophe being reinsured. Any part of a catastrophe loss in excess of $130.0 million would be retained in full. In the event of a catastrophe, OneBeacon's property catastrophe reinsurance program is reinstated for the remainder of the original contract term by paying a reinstatement premium that is based on the percentage of coverage reinstated and the original property catastrophe coverage premium.

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- Definition The entire disclosure pertaining to the existence, magnitude and information about insurance that has been ceded to or assumed from another insurance company, including the methodologies and assumptions used in determining recorded amounts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6816-158387 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27374-158547 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.6,13) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6811-158387 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=34714010&loc=d3e27795-158548 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=34714010&loc=d3e27703-158548 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6485557&loc=d3e21549-158491 + Details
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