XML 95 R45.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Municipal Bond Guarantee Insurance (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2013
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |
Schedule of Municipal Guarantee Insured Obligations [Table Text Block] | The following table provides a schedule of BAM’s insured obligations:
|  | December 31, 2013 |  | December 31, 2012
Contracts issued and outstanding |  | 218 |  |  | 3 |
Remaining weighted average contract period (in years) |  | 13.8 |  |  | 10.4 |
Contractual debt service outstanding (in millions): |  |  |  |
Principal |  | $ | 4,703.7 |  |  | $ | 25.8 |
Interest |  | $ | 3,264.4 |  |  | $ | 8.9 |
Gross unearned insurance premiums |  | $ | 13.2 |  |  | $ | .1 |

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

X
- Definition [Table Text Block] for Schedule of Municipal Guarantee Insured Obligations [Table] + References No definition available. + Details
Name: | wtm_ScheduleOfMunicipalGuaranteeInsuredObligationsTableTextBlock
Namespace Prefix: | wtm_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration