v3.8.0.1

Fair Value of Assets and Liabilities (Nonrecurring Fair Value Measurements) (Details) - Fair Value, Measurements, Nonrecurring - Level 3 - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Commercial mortgage loans |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Realized investment gains (losses) net | $ (2) | $ (5) | $ 0
Carrying value after measurement as of period end | 64 | 47 | 0
Mortgage servicing rights |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Realized investment gains (losses) net | 7 | (1) | (7)
Carrying value after measurement as of period end | 60 | 84 | 90
Cost method investments |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Realized investment gains (losses) net | (29) | (85) | (123)
Carrying value after measurement as of period end | $ 150 | $ 284 | $ 239

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- Definition Amount of addition (reduction) to the amount at which an asset could be incurred (settled) in a current transaction between willing parties. + References No definition available. + Details
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- Definition This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a nonrecurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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