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Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Segment Reporting Information [Line Items] |  |  |  |  |
Earnings before realized gains (losses) and income taxes |  | $ 229 | $ 197 | $ 496 | $ 417
Realized gains (losses) on securities |  | 31 | 8 | (62) | 11
Earnings before income taxes |  | 260 | 205 | 434 | 428
Property and Casualty Insurance |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Property and casualty insurance underwriting |  | 72 | 72 | 163 | 150
Investment and other income, net | [1] | 106 | 91 | 199 | 184
Earnings before realized gains (losses) and income taxes |  | 178 | 163 | 362 | 334
Annuity |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Earnings before realized gains (losses) and income taxes |  | 99 | 85 | 224 | 181
Other |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Earnings before realized gains (losses) and income taxes | [2] | (48) | (51) | (90) | (98)
Specialty Property and transportation | Property and Casualty Insurance |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Property and casualty insurance underwriting |  | 23 | 21 | 56 | 64
Specialty casualty | Property and Casualty Insurance |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Property and casualty insurance underwriting |  | 29 | 29 | 70 | 44
Specialty financial | Property and Casualty Insurance |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Property and casualty insurance underwriting |  | 22 | 23 | 37 | 45
Other specialty | Property and Casualty Insurance |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Property and casualty insurance underwriting |  | (1) | 0 | 2 | (1)
Other lines | Property and Casualty Insurance |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |
Property and casualty insurance underwriting |  | $ (1) | $ (1) | $ (2) | $ (2)
[1] | Includes income of $13 million (before noncontrolling interest) from the sale of a hotel in the first quarter of 2017.
[2] | Includes holding company interest and expenses, including a $7 million loss on retirement of debt in the second quarter of 2017.

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