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Variable Annuity Reinsurance and Weather Derivatives (Details) | 3 Months Ended | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  |  |  |  |  |
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Dec. 31, 2011 USD ($) | Sep. 30, 2011 USD ($) | Jun. 30, 2011 USD ($) | Mar. 31, 2011 USD ($) | Dec. 31, 2010 USD ($) | Sep. 30, 2010 USD ($) | Jun. 30, 2010 USD ($) | Mar. 31, 2010 USD ($) | Dec. 31, 2011 USD ($) | Dec. 31, 2010 USD ($) | Dec. 31, 2009 USD ($) | Dec. 31, 2011 JPY (¥) | Dec. 31, 2011 Fixed income/Interest rate USD ($) | Dec. 31, 2010 Fixed income/Interest rate USD ($) | Dec. 31, 2009 Fixed income/Interest rate USD ($) | Dec. 31, 2010 Foreign exchange USD ($) | Dec. 31, 2010 Equity USD ($) | Dec. 31, 2009 Weather Derivatives USD ($) | Dec. 31, 2011 Level 1 Inputs USD ($) | Dec. 31, 2011 Level 2 Inputs USD ($) | Dec. 31, 2011 Level 3 Inputs USD ($) | Dec. 31, 2011 Fair Value USD ($) | Dec. 31, 2011 Variable annuity reinsurance USD ($) | Dec. 31, 2010 Variable annuity reinsurance USD ($) | Dec. 31, 2009 Variable annuity reinsurance USD ($) | Dec. 31, 2011 Variable annuity reinsurance Level 1 Inputs Foreign exchange Cash Citigroup USD ($) | Dec. 31, 2010 Variable annuity reinsurance Level 1 Inputs Foreign exchange Cash Citigroup USD ($) | Dec. 31, 2009 Variable annuity reinsurance Level 1 Inputs Foreign exchange Cash Citigroup USD ($) | Dec. 31, 2011 Variable annuity reinsurance Level 1 Inputs Equity Cash Citigroup USD ($) | Dec. 31, 2010 Variable annuity reinsurance Level 1 Inputs Equity Cash Citigroup USD ($) | Dec. 31, 2009 Variable annuity reinsurance Level 1 Inputs Equity Cash Citigroup USD ($) | Dec. 31, 2011 WM Life Re USD ($) | Dec. 31, 2010 WM Life Re USD ($) | Dec. 31, 2009 WM Life Re USD ($) | Dec. 31, 2011 WM Life Re Citigroup USD ($) | Dec. 31, 2011 WM Life Re Royal Bank of Scotland USD ($) | Dec. 31, 2011 WM Life Re Bank of America USD ($) | Dec. 31, 2011 WM Life Re JP Morgan Chase USD ($) | Dec. 31, 2011 WM Life Re Nomura USD ($) | Dec. 31, 2011 WM Life Re Barclays USD ($) | Dec. 31, 2011 WM Life Re Goldman Sachs USD ($) | Dec. 31, 2011 WM Life Re Cash USD ($) | Dec. 31, 2010 WM Life Re Cash USD ($) | Dec. 31, 2011 WM Life Re Fixed maturity investments. USD ($) | Dec. 31, 2010 WM Life Re Fixed maturity investments. USD ($) | Dec. 31, 2011 WM Life Re Short-term investments USD ($) | Dec. 31, 2010 WM Life Re Short-term investments USD ($)
Variable annuity reinsurance |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total guarantee value | $ 3,000,000,000 |  |  |  |  |  |  |  | $ 3,000,000,000 |  |  | ¥ 233,700,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Collective account values of underlying variable annuities as a percentage of the guarantee value | 78.00% |  |  |  |  |  |  |  | 78.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Pre-tax operating results of WM Life Re |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fees, included in other revenues |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 32,500,000 | 30,200,000 | 28,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Change in fair value of variable annuity liability, included in other revenues |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7,200,000 | 47,700,000 | 22,400,000 |  |  |  |  |  |  | (156,500,000) | (223,500,000) | 77,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Change in fair value of derivatives, included in other revenues |  |  |  |  |  |  |  |  | 92,900,000 | 127,000,000 | (158,400,000) |  | 8,900,000 | 17,600,000 | 8,000,000 |  |  |  | 10,700,000 | 67,700,000 | 14,500,000 | 92,900,000 |  |  |  | 29,500,000 | 144,600,000 | (69,500,000) | 54,500,000 | (35,200,000) | (96,900,000) | 92,900,000 | 127,000,000 | (158,400,000) |  |  |  |  |  |  |  |  |  |  |  |  |
Foreign exchange, included in other revenues |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 15,100,000 | 21,400,000 | (3,900,000) |  |  |  |  |  |  |  |  |  |  |  |  |
Other investment income and gain (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (900,000) | (900,000) | (1,400,000) |  |  |  |  |  |  |  |  |  |  |  |  |
Total revenues | 593,600,000 | 501,300,000 | 553,600,000 | 529,600,000 | 552,800,000 | 551,000,000 | 670,800,000 | 792,100,000 | 2,178,100,000 | 2,566,700,000 | 3,443,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (16,900,000) | (45,800,000) | (58,100,000) |  |  |  |  |  |  |  |  |  |  |  |  |
Change in fair value of variable annuity death benefit liabilities, included in other expenses |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (1,800,000) | (6,000,000) | 9,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Death benefit claims paid, included in other expenses |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (3,800,000) | (2,700,000) | (2,200,000) |  |  |  |  |  |  |  |  |  |  |  |  |
General and administrative expenses |  |  |  |  |  |  |  |  | (175,300,000) | (155,100,000) | (197,400,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (4,700,000) | (6,300,000) | (5,600,000) |  |  |  |  |  |  |  |  |  |  |  |  |
Pre-tax loss | 58,000,000 | 1,200,000 | 36,100,000 | (33,700,000) | 95,600,000 | 75,200,000 | 5,900,000 | (23,600,000) | 61,600,000 | 153,100,000 | 797,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (27,200,000) | (60,800,000) | (56,600,000) |  |  |  |  |  |  |  |  |  |  |  |  |
Changes in variable annuity liabilities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Balance of liabilities at the beginning of the period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (610,200,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Realized and unrealized gains (losses) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (158,300,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Balance of liabilities at the end of the period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (768,500,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Changes in derivative instruments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Balance of assets at the beginning of the period |  |  |  | 347,500,000 |  |  |  |  | 347,500,000 |  |  |  | 43,900,000 |  |  | 225,300,000 | 78,300,000 |  |  | 72,200,000 | 275,300,000 | 347,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchases |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5,000,000 | 5,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Realized and unrealized gains (losses) |  |  |  |  |  |  |  |  | 92,900,000 | 127,000,000 | (158,400,000) |  | 8,900,000 | 17,600,000 | 8,000,000 |  |  |  | 10,700,000 | 67,700,000 | 14,500,000 | 92,900,000 |  |  |  | 29,500,000 | 144,600,000 | (69,500,000) | 54,500,000 | (35,200,000) | (96,900,000) | 92,900,000 | 127,000,000 | (158,400,000) |  |  |  |  |  |  |  |  |  |  |  |  |
Sales/settlements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (6,600,000) | (100,700,000) | (47,700,000) | (155,000,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Balance of assets at the end of the period | 290,400,000 |  |  |  | 347,500,000 |  |  |  | 290,400,000 | 347,500,000 |  |  | 31,100,000 | 43,900,000 |  | 225,300,000 | 78,300,000 |  | 4,100,000 | 39,200,000 | 247,100,000 | 290,400,000 |  |  |  | 161,300,000 |  |  | 98,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Realized and unrealized derivative gains (losses) recognized in other revenues |  |  |  |  |  |  |  |  | 92,900,000 | 127,000,000 | (158,400,000) |  | 8,900,000 | 17,600,000 | 8,000,000 |  |  |  | 10,700,000 | 67,700,000 | 14,500,000 | 92,900,000 |  |  |  | 29,500,000 | 144,600,000 | (69,500,000) | 54,500,000 | (35,200,000) | (96,900,000) | 92,900,000 | 127,000,000 | (158,400,000) |  |  |  |  |  |  |  |  |  |  |  |  |
Carrying value | 290,400,000 |  |  |  | 347,500,000 |  |  |  | 290,400,000 | 347,500,000 |  |  | 31,100,000 | 43,900,000 |  | 225,300,000 | 78,300,000 |  | 4,100,000 | 39,200,000 | 247,100,000 | 290,400,000 |  |  |  | 161,300,000 |  |  | 98,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Credit risk on derivative instruments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
OTC derivative instruments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 295,400,000 | 351,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Collateral held |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 73,200,000 | 101,000,000 |  |  |  |  |  |  |  |  | (453,500,000) | (291,100,000) | (31,200,000) | (3,300,000) | (600,000) | (31,600,000)
Collateral provided |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 83,000,000 | 25,300,000 |  |  |  |  |  |  |  |  |  |  |  | (48,600,000) | (73,200,000) | (52,400,000)
Cash and short-term investments held and posted as collateral to its reinsurance counterparties |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 485,300,000 | 326,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net exposure to credit losses on fair value of OTC instruments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 305,200,000 | 275,800,000 |  | 67,700,000 | 82,500,000 | 54,200,000 | 34,200,000 | 31,900,000 | 25,100,000 | 9,600,000 |  |  |  |  |  |
Number of creditworthiness ratings |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 21 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Adjustments for counterparty credit risk |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (9,100,000) | (4,000,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |
Weather Derivatives |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net losses recognized on weather derivatives and weather contingent derivatives portfolio |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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- Definition An amount that an insurer adds to a policy's premium, or deducts from a policy's cash value or contract holder's account, as compensation for services rendered; may include fees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.4) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.13(c)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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- Definition Aggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 5 -Section 03 -Paragraph 1 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 + Details
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- Definition Represents cash and short-term investments held and posted as collateral to reinsurance counterparties. + References No definition available. + Details
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- Definition Represents the collective account values of underlying variable annuities as a percentage of the guarantee value of the associated variable annuity reinsurance liability. + References No definition available. + Details
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- Definition The amount of collateral that has been posted against amounts owed by counterparties to over the counter derivative instruments against net derivative instrument positions. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition The amount of collateral held against amounts due to counterparties for over the counter derivative instruments against net derivative instrument positions. + References No definition available. + Details
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- Definition Amount by which fair value of over the counter derivatives has been adjusted for counter party credit risk. + References No definition available. + Details
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- Details
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- Details
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- Definition Purchases that have taken place during the period in relation to derivative assets measured at fair value on a recurring basis. + References No definition available. + Details
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Period Type: | duration

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- Definition Sales and settlements that have taken place during the period in relation to derivative assets measured at fair value on a recurring basis. + References No definition available. + Details
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- Definition This item represents the change in fair value of derivatives due to changes in foreign currency exchange rates, which is included in other revenues. + References No definition available. + Details
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- Definition Net increase or decrease in the fair value of the variable annuity death benefit liabilities included in earnings. + References No definition available. + Details
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- Definition Net increase or decrease in the fair value of the variable annuity liabilities included in earnings. + References No definition available. + Details
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- Definition The net amount as of the balance sheet date of the fair value of derivative assets and derivative liabilities that were not covered by collateral. + References No definition available. + Details
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- Definition Represents the number of creditworthiness ratings used by the entity. + References No definition available. + Details
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- Definition This item represents other investment income and gains (losses) included in earnings for the period. + References No definition available. + Details
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- Definition Total nominal account value guaranteed with certain variable annuities. + References No definition available. + Details
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- Details
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- Details
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