XML 60 R45.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Investment Securities (Net Realized and Unrealized Investment Gains (Losses) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2014 | Sep. 30, 2013 | Sep. 30, 2014 | Sep. 30, 2013
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |  |  |
Trading Securities, Realized Gain (Loss), Total | $ 76.0 | $ 11.7 | $ 128.3 | $ 60.2
Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities | (55.2) | 16.5 | 70.2 | 5.9
Net Realized and Unrealized Gain (Loss) on Trading Securities | 20.8 | 28.2 | 198.5 | 66.1
Income tax expense attributable to net realized and unrealized investment gains | (6.6) | (1.2) | (45.4) | (2.5)
Realized and unrealized gain | 14.2 | 27.0 | 153.1 | 63.6
Fixed maturity investments. |  |  |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |  |  |
Trading Securities, Realized Gain (Loss), Total | 14.5 | (9.4) | 24.2 | (1.5)
Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities | 23.3 | (21.2) | 108.0 | (88.6)
Short-term investments |  |  |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |  |  |
Trading Securities, Realized Gain (Loss), Total | 1.1 | (0.6) | 1.1 | 0.2
Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities | 0 | 0.1 |  |
Common equity securities |  |  |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |  |  |
Trading Securities, Realized Gain (Loss), Total | 54.7 | 20.5 | 92.9 | 57.7
Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities | (69.9) | 33.6 | (43.0) | 84.2
Convertible fixed maturity investments |  |  |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |  |  |
Trading Securities, Realized Gain (Loss), Total | 2.1 | (0.2) | 5.9 | (0.7)
Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities | (3.9) | 2.3 | (5.4) | (0.5)
Other long-term investments |  |  |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |  |  |
Trading Securities, Realized Gain (Loss), Total | 3.3 | 1.9 | 4.0 | 4.8
Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities | (4.7) | 1.7 | 10.6 | 10.8
Forward Contracts |  |  |  |
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |  |  |
Trading Securities, Realized Gain (Loss), Total | $ 0.3 | $ (0.5) | $ 0.2 | $ (0.3)

X
- Definition The sum of the realized and unrealized net gain (loss) on trading securities during the period. + References Reference 1: 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_NetRealizedOrUnrealizedGainLossOnTradingSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Definition Net Realized and Unrealized Gain (Loss) on Trading Securities, Net of Tax + References No definition available. + Details
Name: | wtm_NetRealizedandUnrealizedGainLossonTradingSecuritiesNetofTax
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The aggregate of the change in unrealized holding gain (loss) and foreign currency gain (loss) included in earnings during the reporting period. + References No definition available. + Details
Name: | wtm_NetUnrealizedGainLossandForeignCurrencyGainLossonTradingSecurities
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Tax on net realized and unrealized gains (loss), trading securities + References No definition available. + Details
Name: | wtm_Taxonnetrealizedandunrealizedgainslosstradingsecurities
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Trading Securities, Realized Gain (Loss), Total + References No definition available. + Details
Name: | wtm_TradingSecuritiesRealizedGainLossTotal
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration