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Deferred Policy Acquisition Costs - Progression of deferred policy acquisition costs (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Movement Analysis of Deferred Policy Acquisition Costs and Present Value of Future Profits [Roll Forward] |  |  |  |
Deferred policy acquisition costs and present value of future profits, beginning balance |  | $ 1,239 | $ 1,184 | $ 821
Deferred policy acquisition costs and present value of future profits, additions |  | 817 | 774 | 754
Deferred policy acquisition costs and present value of future profits, periodic amortization |  | (744) | (722) | (710)
Deferred policy acquisition costs and present value of future profits, annuity unlocking |  | 41 | 29 | 35
Deferred policy acquisition costs and present value of future profits, change included in realized gains |  | 10 | 8 | 9
Deferred policy acquisition costs and present value of future profits, sale of subsidiaries |  |  |  | (19)
Deferred policy acquisition costs and present value of future profits, foreign currency translation |  | 0 | (3) | (3)
Deferred policy acquisition costs and present value of future profits, other |  | 10 |  |
Deferred policy acquisition costs and present value of future profits, change in unrealized |  | (157) | (31) | 297
Deferred policy acquisition costs and present value of future profits, ending balance |  | 1,216 | 1,239 | 1,184
Property and casualty insurance |  |  |  |
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward] |  |  |  |
Deferred policy acquisition costs, beginning balance |  | 238 | 226 | 221
Deferred policy acquisition costs, additions |  | 588 | 535 | 519
Deferred policy acquisition costs, periodic amortization |  | (556) | (520) | (511)
Deferred policy acquisition costs, foreign currency translation |  | 0 | (3) | (3)
Deferred policy acquisition costs, ending balance |  | 270 | 238 | 226
Annuity and Run-off Long-term Care and Life |  |  |  |
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward] |  |  |  |
Deferred policy acquisition costs, beginning balance |  | 1,110 | 1,018 | 925
Deferred policy acquisition costs, additions |  | 225 | 230 | 224
Deferred policy acquisition costs, periodic amortization |  | (161) | (169) | (162)
Deferred policy acquisition costs, annuity unlocking |  | 34 | 25 | 31
Deferred policy acquisition costs, change included in realized gains |  | 9 | 6 | 8
Deferred policy acquisition costs, sale of subsidiaries |  |  |  | (8)
Deferred policy acquisition costs, ending balance |  | 1,217 | 1,110 | 1,018
Movement in Deferred Sales Inducements [Roll Forward] |  |  |  |
Deferred sales inducements, beginning balance |  | 110 | 119 | 132
Deferred sales inducements, additions |  | 4 | 9 | 11
Deferred sales inducements, periodic amortization |  | (19) | (24) | (26)
Deferred sales inducements, annuity unlocking |  | 6 | 4 | 4
Deferred sales inducements, change included in realized gains |  | 1 | 2 | 1
Deferred sales inducements, sale of subsidiaries |  |  |  | (3)
Deferred sales inducements, ending balance |  | 102 | 110 | 119
Movement in Present Value of Future Insurance Profits [Roll Forward] |  |  |  |
Present value of future profits, beginning balance |  | 46 | 55 | 74
Present value of future profits, periodic amortization |  | (8) | (9) | (11)
Present value of future profits, annuity unlocking |  | 1 | 0 | 0
Present value of future profits, sale of subsidiaries |  |  |  | (8)
Present value of future profits, other |  | 10 |  |
Present value of future profits, ending balance |  | 49 | 46 | 55
Movement in Unrealized Gains (Losses) Related to Deferred Policy Acquisition Costs and Present Value of Future Profits [Roll Forward] |  |  |  |
Unrealized investment gains (losses), beginning balance | [1] | (265) | (234) | (531)
Unrealized investment gains (losses), change in unrealized | [1] | (157) | (31) | 297
Unrealized investment gains (losses), ending balance | [1] | (422) | (265) | (234)
Movement Analysis of Deferred Policy Acquisition Costs and Present Value of Future Profits [Roll Forward] |  |  |  |
Deferred policy acquisition costs and present value of future profits, beginning balance |  | 1,001 | 958 | 600
Deferred policy acquisition costs and present value of future profits, additions |  | 229 | 239 | 235
Deferred policy acquisition costs and present value of future profits, periodic amortization |  | (188) | (202) | (199)
Deferred policy acquisition costs and present value of future profits, annuity unlocking |  | 41 | 29 | 35
Deferred policy acquisition costs and present value of future profits, change included in realized gains |  | 10 | 8 | 9
Deferred policy acquisition costs and present value of future profits, sale of subsidiaries |  |  |  | (19)
Deferred policy acquisition costs and present value of future profits, other |  | 10 |  |
Deferred policy acquisition costs and present value of future profits, change in unrealized |  | (157) | (31) | 297
Deferred policy acquisition costs and present value of future profits, ending balance |  | 946 | 1,001 | 958
Excluding Unrealized Gains | Annuity and Run-off Long-term Care and Life |  |  |  |
Movement Analysis of Deferred Policy Acquisition Costs and Present Value of Future Profits [Roll Forward] |  |  |  |
Deferred policy acquisition costs and present value of future profits, beginning balance |  | 1,266 | 1,192 | 1,131
Deferred policy acquisition costs and present value of future profits, change in unrealized |  | 0 | 0 | 0
Deferred policy acquisition costs and present value of future profits, ending balance |  | $ 1,368 | $ 1,266 | $ 1,192
[1] | Unrealized adjustments to DPAC includes net unrealized gains/losses on securities and net unrealized gains/losses on cash flow hedges.

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