XML 15 R48.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Investment Securities (Investment Holding Common Equities/ Other Investments) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2014 | Dec. 31, 2013
Investment securities |  |
Fixed maturity investments, at fair value | $ 4,988.7 | $ 5,030.5
Common shareholders' equity. |  |
Investment securities |  |
Cost or amortized cost | 905.6 | 890.2
Trading Securities, Unrealized Holding Gain | 273.9 | 271.0
Trading Securities, Unrealized Holding Loss | (4.5) | (3.6)
Net foreign currency gains (losses) | (0.4) | (0.8)
Fixed maturity investments, at fair value | 1,174.6 | 1,156.8
Convertible Debt Securities |  |
Investment securities |  |
Cost or amortized cost | 64.3 | 71.7
Trading Securities, Unrealized Holding Gain | 10.6 | 9.9
Trading Securities, Unrealized Holding Loss | (1.0) | (0.9)
Net foreign currency gains (losses) | (0.1) | (0.2)
Fixed maturity investments, at fair value | 73.8 | 80.5
Other long-term investments. |  |
Investment securities |  |
Cost or amortized cost | 246.4 | 238.3
Trading Securities, Unrealized Holding Gain | 83.4 | 79.6
Trading Securities, Unrealized Holding Loss | (25.5) | (26.6)
Net foreign currency gains (losses) | (2.0) | (2.4)
Fixed maturity investments, at fair value | $ 302.3 | $ 288.9

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

X
- Definition Cost of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading. + References No definition available. + Details
Name: | us-gaap_TradingSecuritiesCost
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 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 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=6871852&loc=d3e26626-111562 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 -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 Reference 5: 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 + Details
Name: | us-gaap_TradingSecuritiesDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of unrealized holding gain before loss recognized in the income statement for investments in trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.7(c)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e24584-111560 + Details
Name: | us-gaap_TradingSecuritiesUnrealizedHoldingGain
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of unrealized holding loss before gain recognized in the income statement for investments in trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.7(c)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: 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 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e24584-111560 + Details
Name: | us-gaap_TradingSecuritiesUnrealizedHoldingLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The net amount of unrealized gains (losses) from foreign currency transaction adjustments related to trading securities. + References No definition available. + Details
Name: | wtm_TradingSecuritiesNetUnrealizedForeignCurrencyGainLoss
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant