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Investments - Gross unrealized losses and fair value by the type and length of time held in continuous unrealized loss position (Details) $ in Millions | Sep. 30, 2018 USD ($) contract | Dec. 31, 2017 USD ($) contract
--- | --- | ---
U.S. government and agencies |  |
Less than 12 months |  |
Number of issues | contract | 65 | 66
Fair value | $ 2,517 | $ 2,829
Unrealized losses | $ (23) | $ (18)
12 months or more |  |
Number of issues | contract | 26 | 18
Fair value | $ 175 | $ 182
Unrealized losses | (4) | (2)
Total unrealized losses |  |
Total unrealized losses | $ (27) | $ (20)
Municipal |  |
Less than 12 months |  |
Number of issues | contract | 3,192 | 1,756
Fair value | $ 5,600 | $ 3,143
Unrealized losses | $ (75) | $ (24)
12 months or more |  |
Number of issues | contract | 480 | 165
Fair value | $ 667 | $ 349
Unrealized losses | (30) | (12)
Total unrealized losses |  |
Total unrealized losses | $ (105) | $ (36)
Corporate |  |
Less than 12 months |  |
Number of issues | contract | 1,823 | 781
Fair value | $ 24,061 | $ 11,616
Unrealized losses | $ (500) | $ (102)
12 months or more |  |
Number of issues | contract | 329 | 208
Fair value | $ 4,274 | $ 3,289
Unrealized losses | (223) | (102)
Total unrealized losses |  |
Total unrealized losses | $ (723) | $ (204)
Foreign government |  |
Less than 12 months |  |
Number of issues | contract | 26 | 45
Fair value | $ 166 | $ 580
Unrealized losses | $ (2) | $ (10)
12 months or more |  |
Number of issues | contract | 25 | 5
Fair value | $ 432 | $ 44
Unrealized losses | (10) | (1)
Total unrealized losses |  |
Total unrealized losses | $ (12) | $ (11)
Asset-backed securities (“ABS”) |  |
Less than 12 months |  |
Number of issues | contract | 68 | 57
Fair value | $ 442 | $ 476
Unrealized losses | $ (3) | $ (3)
12 months or more |  |
Number of issues | contract | 19 | 9
Fair value | $ 107 | $ 34
Unrealized losses | (5) | (4)
Total unrealized losses |  |
Total unrealized losses | $ (8) | $ (7)
Residential mortgage-backed securities (“RMBS”) |  |
Less than 12 months |  |
Number of issues | contract | 97 | 118
Fair value | $ 21 | $ 35
Unrealized losses | $ 0 | $ (1)
12 months or more |  |
Number of issues | contract | 182 | 181
Fair value | $ 53 | $ 50
Unrealized losses | (2) | (2)
Total unrealized losses |  |
Total unrealized losses | $ (2) | $ (3)
Commercial mortgage-backed securities (“CMBS”) |  |
Less than 12 months |  |
Number of issues | contract | 5 | 2
Fair value | $ 18 | $ 1
Unrealized losses | $ 0 | $ 0
12 months or more |  |
Number of issues | contract | 3 | 6
Fair value | $ 1 | $ 23
Unrealized losses | (1) | (2)
Total unrealized losses |  |
Total unrealized losses | $ (1) | $ (2)
Redeemable preferred stock |  |
Less than 12 months |  |
Number of issues | contract |  | 1
Fair value |  | $ 0
Unrealized losses |  | $ 0
12 months or more |  |
Number of issues | contract |  | 0
Fair value |  | $ 0
Unrealized losses |  | 0
Total unrealized losses |  |
Total unrealized losses |  | $ 0
Fixed income securities |  |
Less than 12 months |  |
Number of issues | contract | 5,276 | 2,826
Fair value | $ 32,825 | $ 18,680
Unrealized losses | $ (603) | $ (158)
12 months or more |  |
Number of issues | contract | 1,064 | 592
Fair value | $ 5,709 | $ 3,971
Unrealized losses | (275) | (125)
Total unrealized losses |  |
Total unrealized losses | (878) | $ (283)
Equity securities |  |
Less than 12 months |  |
Number of issues | contract |  | 127
Fair value |  | $ 369
Unrealized losses |  | $ (12)
12 months or more |  |
Number of issues | contract |  | 2
Fair value |  | $ 0
Unrealized losses |  | 0
Total unrealized losses |  |
Total unrealized losses |  | $ (12)
Fixed income and equity securities |  |
Less than 12 months |  |
Number of issues | contract |  | 2,953
Fair value |  | $ 19,049
Unrealized losses |  | $ (170)
12 months or more |  |
Number of issues | contract |  | 594
Fair value |  | $ 3,971
Unrealized losses |  | (125)
Total unrealized losses |  |
Total unrealized losses | $ (878) | $ (295)
Investment grade fixed income securities |  |
Less than 12 months |  |
Number of issues | contract | 4,939 | 2,706
Fair value | $ 30,338 | $ 17,668
Unrealized losses | $ (529) | $ (134)
12 months or more |  |
Number of issues | contract | 1,015 | 535
Fair value | $ 5,461 | $ 3,751
Unrealized losses | (253) | (98)
Total unrealized losses |  |
Total unrealized losses | $ (782) | $ (232)
Below investment grade fixed income securities |  |
Less than 12 months |  |
Number of issues | contract | 337 | 120
Fair value | $ 2,487 | $ 1,012
Unrealized losses | $ (74) | $ (24)
12 months or more |  |
Number of issues | contract | 49 | 57
Fair value | $ 248 | $ 220
Unrealized losses | (22) | (27)
Total unrealized losses |  |
Total unrealized losses | $ (96) | $ (51)

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