XML 169 R149.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Discontinued Operations (Assets and Liabilities Classified as Held for Sale) (Details) - USD ($) $ in Millions | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
--- | --- | --- | --- | ---
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Deferred Income Tax Assets, Net | $ 112.8 | $ 114.6 |  |
Assets held for sale |  |  |  |
Fixed maturity investments, at fair value | 2,639.7 | 2,422.0 |  |
Short-term investments, at amortized cost (which approximates fair value) | 211.3 | 376.8 |  |
Common equity securities, at fair value | 1,113.9 | 611.7 |  |
Other long-term investments | 315.8 | 331.9 |  |
Total investments | 4,280.7 | 3,742.4 |  |
Insurance premiums receivable | 223.3 | 241.1 |  |
Ceded unearned insurance premiums | 29.5 | 17.8 |  |
Accounts receivable on unsettled investment sales | 41.9 | 37.8 |  |
Goodwill and intangible assets | 375.7 | 351.2 |  |
Other assets | 318.7 | 348.7 |  |
Assets held for sale | 4,407.0 | 4,630.6 |  |
Deferred acquisition costs | 107.6 | 107.2 |  |
Cash Including Restricted Cash | 179.3 | 261.7 |  |
Liabilities held for sale |  |  |  |
Loss and loss adjustment expense reserves | 1,395.8 | 1,350.0 | $ 1,054.3 | $ 1,000.0
Unearned insurance premiums | 612.6 | 616.7 |  |
Debt | 442.4 | 343.1 |  |
Deferred tax liability | 7.0 | 0.0 |  |
Accrued incentive compensation | 141.7 | 108.1 |  |
Ceded reinsurance payable | 30.5 | 34.2 |  |
Funds held under insurance contracts | 137.8 | 81.0 |  |
Accounts payable on unsettled investment purchases | 0.0 | 0.5 |  |
Other liabilities | 264.7 | 278.4 |  |
Liabilities held for sale | 2,884.0 | 3,105.3 |  |
Reinsurance recoverable on unpaid losses | 186.5 | 161.7 |  |
Reinsurance recoverable on paid losses | 7.5 | 12.2 |  |
Sirius Group |  |  |  |
Assets held for sale |  |  |  |
Total investments | 686.2 |  |  |
Cash Including Restricted Cash | 143.9 | 111.5 | $ 93.2 | $ 93.7
Sirius Group | Discontinued Operations |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Deferred Income Tax Assets, Net | 303.1 | 341.5 |  |
Assets held for sale |  |  |  |
Fixed maturity investments, at fair value | 2,374.0 | 2,362.3 |  |
Short-term investments, at amortized cost (which approximates fair value) | 352.0 | 494.9 |  |
Common equity securities, at fair value | 174.4 | 189.9 |  |
Other long-term investments | 72.2 | 95.6 |  |
Total investments | 2,972.6 | 3,142.7 |  |
Insurance premiums receivable | 323.6 | 306.6 |  |
Ceded unearned insurance premiums | 87.7 | 76.2 |  |
Accounts receivable on unsettled investment sales | 29.0 | 18.7 |  |
Goodwill and intangible assets | 10.2 | 15.2 |  |
Other assets | 169.0 | 156.6 |  |
Assets held for sale | 4,407.0 | 4,630.6 |  |
Deferred acquisition costs | 74.6 | 69.9 |  |
Cash Including Restricted Cash | 143.9 | 111.5 |  |
Liabilities held for sale |  |  |  |
Loss and loss adjustment expense reserves | 1,644.4 | 1,809.8 |  |
Unearned insurance premiums | 342.2 | 338.6 |  |
Debt | 403.5 | 403.5 |  |
Deferred tax liability | 263.6 | 282.8 |  |
Accrued incentive compensation | 63.2 | 76.5 |  |
Ceded reinsurance payable | 67.1 | 71.5 |  |
Funds held under insurance contracts | 52.9 | 57.9 |  |
Accounts payable on unsettled investment purchases | 0.0 | 2.1 |  |
Other liabilities | 47.1 | 62.6 |  |
Liabilities held for sale | 2,884.0 | 3,105.3 |  |
Net assets held for sale | 1,523.0 | 1,525.3 |  |
Reinsurance recoverable on unpaid losses | 283.1 | 322.2 |  |
Reinsurance recoverable on paid losses | 10.2 | 11.4 |  |
OneBeacon Runoff | Discontinued Operations |  |  |  |
Assets held for sale |  |  |  |
Other assets | $ 0.0 | $ 58.1 |  |

X
- References No definition available. + Details
Name: | us-gaap_AssetsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of other assets held-for-sale that are not part of a disposal group. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 15 -Paragraph 4 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=6390208&loc=d3e400-110220 + Details
Name: | us-gaap_AssetsHeldForSaleNotPartOfDisposalGroupOther
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of net assets (liabilities). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 225 -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09.6,7) -URI http://asc.fasb.org/extlink&oid=6488393&loc=d3e606914-122999 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35686370&loc=SL35686385-199418 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 210 -Section S99 -Paragraph 2 -Subparagraph (SX 210.6-05.4) -URI http://asc.fasb.org/extlink&oid=6488278&loc=d3e604008-122996 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 09 -Paragraph 19 -Article 6 + Details
Name: | us-gaap_AssetsNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, netted by jurisdiction. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319 + Details
Name: | us-gaap_DeferredIncomeTaxAssetsNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Net amount of deferred policy acquisition costs capitalized on contracts remaining in force as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 825 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6487548&loc=d3e32546-158582 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 30 -Section 55 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=51660407&loc=d3e11446-158418 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6481648&loc=d3e11198-158413 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),7) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 16 -Article 12 + Details
Name: | us-gaap_DeferredPolicyAcquisitionCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of funds held as security for payments to be received under reinsurance contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.13(c)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
Name: | us-gaap_FundsHeldUnderReinsuranceAgreementsLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Carrying amount of finite-lived intangible assets, indefinite-lived intangible assets and goodwill. Goodwill is an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. Intangible assets are assets, not including financial assets, lacking physical substance. + References No definition available. + Details
Name: | us-gaap_IntangibleAssetsNetIncludingGoodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Sum of the carrying amounts as of the balance sheet date of all investments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(h)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
Name: | us-gaap_Investments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_LiabilitiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. + 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),(b),(c) -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437 + Details
Name: | us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.16) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 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 210.7-03.16) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 + Details
Name: | us-gaap_LongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The aggregate carrying amounts, as of the balance sheet date, of assets not separately disclosed in the balance sheet. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 10 -Article 7 + Details
Name: | us-gaap_OtherAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The aggregate carrying amount, as of the balance sheet date, of liabilities not separately disclosed in the balance sheet. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.15) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
Name: | us-gaap_OtherLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Other long-term investments not otherwise specified in the taxonomy, not including investments in marketable securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(f)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_OtherLongTermInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount payable to broker-dealers and clearing organizations, including, but not limited to, securities failed-to-receive, certain deposits received for securities loaned, open transactions, and floor-brokerage payables. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 20 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=35710130&loc=d3e41645-110958 + Details
Name: | us-gaap_PayablesToBrokerDealersAndClearingOrganizations
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The carrying amount as of the balance sheet date due the entity from (a) agents and insureds, (b) uncollected premiums and (c) others, net of the allowance for doubtful accounts. + References Reference 1: 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),5) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
Name: | us-gaap_PremiumsReceivableAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The unexpired portion of premiums ceded on policies in force as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Prepaid Reinsurance Premiums -URI http://asc.fasb.org/extlink&oid=6521719 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 340 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6485982&loc=d3e22818-158507 + Details
Name: | us-gaap_PrepaidReinsurancePremiums
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount receivable from broker-dealers and clearing organizations, including, but not limited to, securities failed-to-deliver, certain deposits for securities borrowed, open transactions, good faith and margin deposits, commissions and floor brokerage receivables. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 20 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=35710130&loc=d3e41645-110958 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522 + Details
Name: | us-gaap_ReceivablesFromBrokersDealersAndClearingOrganizations
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The carrying amount as of the balance sheet date of the known and estimated amounts owed to insurers under reinsurance treaties or other arrangements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.13(a)(3),(c)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
Name: | us-gaap_ReinsurancePayable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount after valuation allowance of reinsurance recoverables on paid losses. + References Reference 1: 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
Name: | us-gaap_ReinsuranceRecoverablesOnPaidLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount after valuation allowance of reinsurance recoverables for losses reported to the ceding insurer but not yet paid, amounts expected of incurred losses and settlement expenses, which have not yet been reported to the ceding insurer. + References Reference 1: 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
Name: | us-gaap_ReinsuranceRecoverablesOnUnpaidLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Subparagraph g -Article 7 + Details
Name: | us-gaap_ShortTermInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investments in debt securities classified as trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.4) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26626-111562 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 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),1) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562 + Details
Name: | us-gaap_TradingSecuritiesDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investments in trading equity securities and other forms of trading securities that provide ownership interests. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26626-111562 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.4) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 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),1(b)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 + Details
Name: | us-gaap_TradingSecuritiesEquity
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount of premiums written on insurance contracts that have not been earned as of the balance sheet date. + References Reference 1: 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(a)(2)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 16 -Article 12 + Details
Name: | us-gaap_UnearnedPremiums
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This item includes unrestricted cash available for day-to-day operating needs and cash that is restricted as to withdrawal or usage. + References No definition available. + Details
Name: | wtm_CashIncludingRestrictedCash
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Deferred Tax Liability, Net of Valuation Allowance + References No definition available. + Details
Name: | wtm_DeferredTaxLiabilityNetofValuationAllowance
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Aggregate carrying value as of the balance sheet date of liabilities for incentive compensation arrangements. + References No definition available. + Details
Name: | wtm_IncentiveCompensationPayable
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Liabilities related to a disposition that have been classified as Held for Sale. + References No definition available. + Details
Name: | wtm_LiabilitiesHeldForSale
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=wtm_SiriusGroupMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementOperatingActivitiesSegmentAxis=us-gaap_SegmentDiscontinuedOperationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=wtm_OnebeaconRunoffMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |