XML 115 R68.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Reserves for Unpaid Losses and Loss Adjustment Expenses (LAE Reserve Activity) (Details) (Sirius Group, USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Gross |  |  |
Beginning balance | $ 228.6 | $ 207.2 | $ 214.3
Losses and LAE acquired | 14.0 | 11.7 | 0
Incurred losses and LAE | 12.9 | 46.7 | 16.5
Paid losses and LAE | (27.7) | (37.0) | (23.6)
Ending balance | 227.8 | 228.6 | 207.2
Net |  |  |
Beginning balance | 189.4 | 162.7 | 169.6
Losses and LAE acquired Central National | 14.0 | 11.7 | 0
Incurred losses and LAE | 12.6 | 45.9 | 12.3
Liability for unpaid claims and claims adjustment expense | (22.1) | (30.9) | (19.2)
Ending balance | 193.9 | 189.4 | 162.7
Asbestos |  |  |
Gross |  |  |
Beginning balance | 208.2 | 185.1 | 191.9
Losses and LAE acquired | 13.0 | 11.0 | 0
Incurred losses and LAE | 12.1 | 46.8 | 13.6
Paid losses and LAE | (25.9) | (34.7) | (20.4)
Ending balance | 207.4 | 208.2 | 185.1
Net |  |  |
Beginning balance | 174.2 | 146.2 | 151.5
Losses and LAE acquired Central National | 13.0 | 11.0 | 0
Incurred losses and LAE | 11.8 | 46.4 | 10.3
Liability for unpaid claims and claims adjustment expense | (20.3) | (29.4) | (15.6)
Ending balance | 178.7 | 174.2 | 146.2
Environmental |  |  |
Gross |  |  |
Beginning balance | 20.4 | 22.1 | 22.4
Losses and LAE acquired | 1.0 | 0.7 | 0
Incurred losses and LAE | 0.8 | (0.1) | 2.9
Paid losses and LAE | (1.8) | (2.3) | (3.2)
Ending balance | 20.4 | 20.4 | 22.1
Net |  |  |
Beginning balance | 15.2 | 16.5 | 18.1
Losses and LAE acquired Central National | 1.0 | 0.7 | 0
Incurred losses and LAE | 0.8 | (0.5) | 2.0
Liability for unpaid claims and claims adjustment expense | (1.8) | (1.5) | (3.6)
Ending balance | $ 15.2 | $ 15.2 | $ 16.5

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 + 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 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 FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14784-158437 + 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 + 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 + 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 + 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 + Details
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsNetIncurredLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsNetRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
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 Increase in asbestos and environmental reserve due to acquisition of Central National, before estimated recoveries from reinsurers. + References No definition available. + Details
Name: | wtm_LiabilityForAsbestosAndEnvironmentalClaimsAcquiredGross
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Increase in asbestos and environmental reserve due to acquisition of Central National, after estimated recoveries from reinsurers. + References No definition available. + Details
Name: | wtm_LiabilityForAsbestosAndEnvironmentalClaimsAcquiredNet
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration