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Investments - Narrative (Details) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2017 USD ($) | Sep. 30, 2016 USD ($) | Sep. 30, 2017 USD ($) security | Sep. 30, 2016 USD ($) | Dec. 31, 2016 USD ($)
Investment [Line Items] |  |  |  |  |
Percentage (based on amount of unrealized loss) of available for sale fixed maturities that are in an unrealized loss position and rated investment grade |  |  | 73.00% |  |
Percentage (based on fair value) of available for sale fixed maturities that are in an unrealized loss position and rated investment grade |  |  | 88.00% |  |
Other than temporary impairment charges | $ 38 | $ 16 | $ 53 | $ 107 |
Fixed maturities — all other |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Other than temporary impairment charges |  |  | 1 |  |
Residential MBS |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Non-credit related portion of other-than-temporary impairment charges taken for securities still owned | 165 |  | 165 |  | $ 189
Gross unrealized losses on fixed maturities | (7) |  | (7) |  | (13)
Other than temporary impairment charges |  |  | 1 |  |
Securities with non-credit other-than-temporary impairment charges |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Gross unrealized gains | 141 |  | 141 |  | 130
Gross unrealized losses | (4) |  | (4) |  | (3)
Fixed maturities |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Gross unrealized losses on fixed maturities | (85) |  | $ (85) |  | (245)
Number of available for sale securities in an unrealized loss position | security |  |  | 735 |  |
Other than temporary impairment charges | 15 | $ 2 | $ 16 | $ 37 |
Corporate bonds |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Other than temporary impairment charges |  |  | $ 15 |  |
Common stocks |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Number of available for sale securities in an unrealized loss position | security |  |  | 19 |  |
Other than temporary impairment charges |  |  | $ 42 |  |
Gross unrealized losses on equity securities | (27) |  | $ (27) |  | (23)
Preferred stocks |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Number of available for sale securities in an unrealized loss position | security |  |  | 5 |  |
Other than temporary impairment charges |  |  | $ 7 |  |
Gross unrealized losses on equity securities | $ (1) |  | $ (1) |  | $ (7)
Number of available for sale securities in an unrealized loss position for twelve months or longer | Common stocks |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Number of available for sale securities in an unrealized loss position | security |  |  | 0 |  |
Number of available for sale securities in an unrealized loss position for twelve months or longer | Preferred stocks |  |  |  |  |
Investment [Line Items] |  |  |  |  |
Number of available for sale securities in an unrealized loss position | security |  |  | 3 |  |

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- Definition Line items represent reporting 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 Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 12 -Sentence Column A + Details
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