XML 25 R142.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Discontinued Operations Discontinued Operations (Asbestos and environmental loss and LAE reserve activity) (Details) (OneBeacon Runoff, USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Gross |  |  |  |  |  |
Beginning balance | $ 1,354.1 |  | $ 1,023.0 |  | $ 1,336.3 |
Incurred losses and LAE | (1.2) |  | 488.6 |  | 6.2 |
Paid losses and LAE | (190.5) |  | (157.5) |  | (319.5) |
Ending balance | 1,162.4 |  | 1,354.1 |  | 1,023.0 |
Beginning balance | 832.8 | [1] | 741.1 | [1] | 907.4 | [1]
Incurred losses and LAE | (1.0) | [1] | 94.4 | [1] | 6.0 | [1]
Paid losses and LAE | (103.9) | [1] | (2.7) | [1] | (172.3) | [1]
Ending balance | 727.9 | [1] | 832.8 | [1] | 741.1 | [1]
Beginning balance | 11.2 | [2] | 15.6 | [2] | 14.1 | [2]
Incurred losses and LAE | (1.0) | [2] | 6.0 | [2] | 6.0 | [2]
Liability for unpaid claims and claims adjustment expense | 1.4 | [2] | 10.4 | [2] | 4.5 | [2]
Ending balance | 8.8 | [2] | 11.2 | [2] | 15.6 | [2]
Asbestos Issue |  |  |  |  |  |
Gross |  |  |  |  |  |
Beginning balance | 1,074.3 |  | 904.0 |  | 985.6 |
Incurred losses and LAE | (0.3) |  | 256.8 |  | 0 |
Paid losses and LAE | (144.6) |  | (86.5) |  | (81.6) |
Ending balance | 929.4 |  | 1,074.3 |  | 904.0 |
Beginning balance | 681.2 | [1] | 647.3 | [1] | 688.8 | [1]
Incurred losses and LAE | (0.5) | [1] | 32.2 | [1] | 0 | [1]
Paid losses and LAE | (78.2) | [1] | 1.7 | [1] | (41.5) | [1]
Ending balance | 602.5 | [1] | 681.2 | [1] | 647.3 | [1]
Beginning balance | 2.2 | [2] | 6.4 | [2] | 6.5 | [2]
Incurred losses and LAE | (0.5) | [2] | (4.0) | [2] | 0 | [2]
Liability for unpaid claims and claims adjustment expense | (0.7) | [2] | 0.2 | [2] | 0.1 | [2]
Ending balance | 2.4 | [2] | 2.2 | [2] | 6.4 | [2]
Environmental Issue |  |  |  |  |  |
Gross |  |  |  |  |  |
Beginning balance | 279.8 |  | 119.0 |  | 350.7 |
Incurred losses and LAE | (0.9) |  | 231.8 |  | 6.2 |
Paid losses and LAE | (45.9) |  | (71.0) |  | (237.9) |
Ending balance | 233.0 |  | 279.8 |  | 119.0 |
Beginning balance | 151.6 | [1] | 93.8 | [1] | 218.6 | [1]
Incurred losses and LAE | (0.5) | [1] | 62.2 | [1] | 6.0 | [1]
Paid losses and LAE | (25.7) | [1] | (4.4) | [1] | (130.8) | [1]
Ending balance | 125.4 | [1] | 151.6 | [1] | 93.8 | [1]
Beginning balance | 9.0 | [2] | 9.2 | [2] | 7.6 | [2]
Incurred losses and LAE | (0.5) | [2] | 10.0 | [2] | 6.0 | [2]
Liability for unpaid claims and claims adjustment expense | 2.1 | [2] | 10.2 | [2] | 4.4 | [2]
Ending balance | $ 6.4 | [2] | $ 9.0 | [2] | $ 9.2 | [2]
[1] | Represents A&E reserve activity, net of third-party reinsurance, but prior to the NICO Cover.
[2] | Includes NICO cover

X
- Definition Carrying amount as of the balance sheet date of reserves for the costs of settling insured claims and costs incurred in the claims settlement process attributable to asbestos and environmental claims, before estimated recoveries from reinsurers. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Audit and Accounting Guide (AAG) -Number AAG-PLI -Paragraph 132, 133, 135, 136, 137 -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. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 94-5 -Paragraph 11, 12 -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
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of asbestos claims paid in the current period, before estimated recoveries from reinsurers. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 94-5 -Paragraph 11, 12 -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 FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14784-158437 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Audit and Accounting Guide (AAG) -Number AAG-PLI -Paragraph 132, 133, 135, 136, 137 -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
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsGrossClaimsPaid
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Increase in asbestos and environmental reserve based on known and estimated costs of settling insured claims and costs incurred in the claims settlement process, before estimated recoveries from reinsurers. + References Reference 1: 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 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Audit and Accounting Guide (AAG) -Number AAG-PLI -Paragraph 132, 133, 135, 136, 137 -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. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 94-5 -Paragraph 11, 12 -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
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsGrossIncurredLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Carrying amount as of the balance sheet date of reserves for the costs of settling insured claims and costs incurred in the claims settlement process attributable to asbestos and environmental claims, net of estimated reinsurance recoveries. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Audit and Accounting Guide (AAG) -Number AAG-PLI -Paragraph 132, 133, 135, 136, 137 -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. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 94-5 -Paragraph 11, 12 -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
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of asbestos claims paid in the current period, net of reinsurance recoveries. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Audit and Accounting Guide (AAG) -Number AAG-PLI -Paragraph 132, 133, 135, 136, 137 -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. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 94-5 -Paragraph 11, 12 -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
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsNetClaimsPaid
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Increase in asbestos and environmental reserve based on known and estimated costs of settling insured claims and costs incurred in the claims settlement process, net of estimated reinsurance recoveries. + References Reference 1: 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 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Audit and Accounting Guide (AAG) -Number AAG-PLI -Paragraph 132, 133, 135, 136, 137 -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. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 94-5 -Paragraph 11, 12 -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
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsNetIncurredLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Carrying amount as of the balance sheet date of reserves for the costs of settling insured claims and costs incurred in the claims settlement process attributable to asbestos and environmental claims, net of estimated reinsurance recoveries except NICO cover. + References No definition available. + Details
Name: | wtm_LiabilityForAsbestosAndEnvironmentalClaimsNetBeforeNico
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of asbestos claims paid in the current period, net of reinsurance recoveries except NICO cover. + References No definition available. + Details
Name: | wtm_LiabilityForAsbestosAndEnvironmentalClaimsNetClaimsPaidBeforeNico
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Increase in asbestos and environmental reserve based on known and estimated costs of settling insured claims and costs incurred in the claims settlement process, net of estimated reinsurance recoveries except NICO cover. + References No definition available. + Details
Name: | wtm_LiabilityForAsbestosAndEnvironmentalClaimsNetIncurredLossBeforeNico
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration