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Discontinued Operations (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 12 Months Ended | 1 Months Ended | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2012 | Sep. 30, 2012 | Jun. 30, 2012 | Mar. 31, 2012 | Dec. 31, 2011 | Sep. 30, 2011 | Jun. 30, 2011 | Mar. 31, 2011 | Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2012 OneBeacon Runoff | Dec. 31, 2012 OneBeacon | Dec. 31, 2011 OneBeacon | Dec. 31, 2010 OneBeacon | Dec. 31, 2012 Discontinued Operations | Dec. 31, 2011 Discontinued Operations | Dec. 31, 2010 Discontinued Operations | Dec. 31, 2012 Loss attributable to change in discount rate OneBeacon Runoff | Oct. 31, 2011 Esurance | Dec. 31, 2012 Esurance | Dec. 31, 2011 Esurance | Dec. 31, 2010 Esurance | Dec. 31, 2012 Esurance Discontinued Operations | Dec. 31, 2011 Esurance Discontinued Operations | Dec. 31, 2010 Esurance Discontinued Operations | Feb. 22, 2012 AutoOne Entity | Dec. 31, 2012 AutoOne Discontinued Operations | Dec. 31, 2011 AutoOne Discontinued Operations | Dec. 31, 2012 OneBeacon Runoff Contract | Dec. 31, 2012 OneBeacon Runoff GRC Cover | Dec. 31, 2012 OneBeacon Runoff NICO Cover | May 31, 2001 OneBeacon Runoff General Reinsurance Corporation GRC Cover | Dec. 31, 2012 OneBeacon Runoff Discontinued Operations | Dec. 31, 2011 OneBeacon Runoff Discontinued Operations | Dec. 31, 2010 OneBeacon Runoff Discontinued Operations
Reinsurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on sale of discontinued operation, net of tax |  |  |  |  |  |  |  |  |  |  |  | $ (91.5) |  |  |  | $ (91.0) | $ (19.2) | $ 0 |  | $ 677.5 | $ 0 | $ 677.5 | $ 0 | $ 0 | $ 677.5 | $ 0 |  | $ 0.5 | $ (19.2) |  |  |  |  |  |  |
Number of insurance companies sold |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |
Net (loss) income from discontinued operations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (115.0) | 621.6 | (30.1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss and LAE incurred relating prior year losses |  |  |  |  |  |  |  |  | 41.9 | 76.7 | 93.1 |  | 7.4 | 29.8 | 36.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (40.0) | (26.7) | (23.1)
Workers compensation discount amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4.50% | 3.50% |
Workers compensation discount percent |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 15.2 |  |
Net loss from other discontinued operations, net of tax | 0.5 | (106.8) | 0.5 | (9.2) | 647.6 | (30.1) | (2.4) | 6.5 | (24.0) | (36.7) | (30.1) |  |  |  |  | (24.0) | (36.7) | (30.1) | (9.0) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of contracts seller caused One Beacon to purchase prior to acquisition |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |
Reinsurance recoverable cover under reinsurance contract |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 570.0 | 2,500.0 |  |  |  |
Adverse loss reserve development |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 400.0 |  |  |
Loss reserves ceded at acquisition |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 170.0 |  |  |
Reinsurance recoverable on paid and unpaid losses | 447.0 |  |  |  | 2,537.8 |  |  |  | 447.0 | 2,537.8 |  |  | 110.7 | 2,184.1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,401.9 |  |
Reinsurance recoverable on paid losses | 17.9 |  |  |  | 30.5 |  |  |  | 17.9 | 30.5 |  |  | 3.3 |  |  | 15.6 | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 15.6 |  |
Reinsurance recoverables |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,840.8 |  |
Purchase accounting adjustments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 150.1 |  |
Amount of held for sale to be reinsured at closing |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 36.7 |  |

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- Definition Amount of provision in the period for claims incurred in prior reporting periods and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Financial Reporting Release (FRR) -Number 403 -Paragraph 04 -Subparagraph b Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 94-5 -Paragraph 11 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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- Definition Receivables currently due from reinsurers for ceded claims paid. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6485522&loc=d3e21409-158489 Reference 2: 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) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 14, 15 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 6 -Article 7 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6485522&loc=d3e21412-158489 + Details
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- Definition The known and estimated amount recoverable as of the balance sheet date from reinsurers for claims paid or incurred by the ceding insurer and associated claims settlement expenses, including estimated amounts for claims incurred but not reported, and policy benefits, net of any related valuation allowance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 14, 16, 27, 113 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 6 -Article 7 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6824-158387 Reference 4: 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.(a),6) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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- Definition Current year monetary amount of the change in worker's compensation reserve liability resulting from the discount applied to reduce the reserve to present value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 13 -Subparagraph b -Article 7 Reference 2: 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.(a),13(b)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Audit and Accounting Guide (AAG) -Number AAG-PLI -Paragraph 4 -IssueDate 2006-09-01 -Chapter 4 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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- Definition Represents the number of reinsurance contracts the seller caused OneBeacon to purchase from subsidiaries of Berkshire Hathaway Inc. immediately prior to the entity's acquisition of OneBeacon. + References No definition available. + Details
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