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Investments - Available for sale fixed maturities (Details) - USD ($) $ in Millions | Sep. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Fixed maturities, Available for sale, Amortized Cost | $ 40,053 | $ 37,038
Available for sale (AFS) fixed maturities | 40,244 | 38,379
Total fixed maturities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fixed maturities, Available for sale, Amortized Cost | 40,053 | 37,038
Fixed maturities, Available for sale, Gross Unrealized, Gains | 734 | 1,423
Fixed maturities, Available for sale, Gross Unrealized, Losses | (543) | (82)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses) | 191 | 1,341
Available for sale (AFS) fixed maturities | 40,244 | 38,379
U.S. Government and government agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fixed maturities, Available for sale, Amortized Cost | 238 | 244
Fixed maturities, Available for sale, Gross Unrealized, Gains | 0 | 1
Fixed maturities, Available for sale, Gross Unrealized, Losses | (4) | (3)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses) | (4) | (2)
Available for sale (AFS) fixed maturities | 234 | 242
States, municipalities and political subdivisions |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fixed maturities, Available for sale, Amortized Cost | 6,756 | 6,887
Fixed maturities, Available for sale, Gross Unrealized, Gains | 117 | 254
Fixed maturities, Available for sale, Gross Unrealized, Losses | (98) | (18)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses) | 19 | 236
Available for sale (AFS) fixed maturities | 6,775 | 7,123
Foreign government |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fixed maturities, Available for sale, Amortized Cost | 137 | 124
Fixed maturities, Available for sale, Gross Unrealized, Gains | 2 | 3
Fixed maturities, Available for sale, Gross Unrealized, Losses | 0 | 0
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses) | 2 | 3
Available for sale (AFS) fixed maturities | 139 | 127
Residential MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fixed maturities, Available for sale, Amortized Cost | 2,408 | 2,884
Fixed maturities, Available for sale, Gross Unrealized, Gains | 310 | 349
Fixed maturities, Available for sale, Gross Unrealized, Losses | (9) | (6)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses) | 301 | 343
Available for sale (AFS) fixed maturities | 2,709 | 3,227
Commercial MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fixed maturities, Available for sale, Amortized Cost | 913 | 927
Fixed maturities, Available for sale, Gross Unrealized, Gains | 14 | 36
Fixed maturities, Available for sale, Gross Unrealized, Losses | (4) | (1)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses) | 10 | 35
Available for sale (AFS) fixed maturities | 923 | 962
Asset-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fixed maturities, Available for sale, Amortized Cost | 9,249 | 7,836
Fixed maturities, Available for sale, Gross Unrealized, Gains | 122 | 142
Fixed maturities, Available for sale, Gross Unrealized, Losses | (64) | (16)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses) | 58 | 126
Available for sale (AFS) fixed maturities | 9,307 | 7,962
Corporate and other |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fixed maturities, Available for sale, Amortized Cost | 20,352 | 18,136
Fixed maturities, Available for sale, Gross Unrealized, Gains | 169 | 638
Fixed maturities, Available for sale, Gross Unrealized, Losses | (364) | (38)
Fixed maturities, Available for sale, Net Unrealized, Gains (Losses) | (195) | 600
Available for sale (AFS) fixed maturities | $ 20,157 | $ 18,736

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- Definition Amount before tax of net unrealized gain (loss) in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale. + References No definition available. + Details
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