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Investments (Net investment income) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2013 | Mar. 31, 2012
Gross investment income | $ 645 | $ 662
Investment expense | (12) | (14)
Net investment income | 633 | 648
Fixed maturity securities [Member] |  |
Gross investment income | 499 | 516
Short term investments [Member] |  |
Gross investment income | 1 | 1
Limited partnership investments [Member] |  |
Gross investment income | 131 | 130
Equity securities [Member] |  |
Gross investment income | 3 | 4
Mortgage loans [Member] |  |
Gross investment income | 5 | 3
Trading portfolio [Member] |  |
Gross investment income | 5 | 7
Other [Member] |  |
Gross investment income | $ 1 | $ 1

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- Definition Investment Income Including Realized Gains Losses on Trading Securities, Before Expenses + References No definition available. + Details
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- Definition The income earned from investments in securities and property, equipment and other capital assets. It includes rent from property and equipment, dividends from shares in corporations, and interest from bonds, loans, mortgages, derivatives, commercial paper, bank accounts, certificates of deposits, treasuries, and other financial securities. It also includes realized gains and losses on trading securities. + References No definition available. + Details
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- Definition Total expenses related to the generation of investment income in debt and equity 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 210.5-03.9) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 + Details
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