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Investments (Net Realized Gains (Losses) And Losses Included In Net Realized Gains (Losses) And Other Comprehensive Income) (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Gain (Loss) on Securities [Line Items] |  |  |  |
OTTI on fixed maturities, gross | $ 14 | $ 8 | $ 19 | $ 36
OTTI on fixed maturities recognized in OCI (pre-tax) | 3 | 0 | 3 | 1
Cost-method Investments, Realized Gain (Loss) | 19 | (10) | 35 | 84
Foreign exchange gains (losses) | 39 | 15 | 102 | 10
Gain (Loss) on Derivative | (17) | (22) | 91 | 68
Fair Value Adjustments On Insurance Derivative Gains Losses | 54 | 54 | 133 | 265
Investment and embedded derivative instruments |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Gain (Loss) on Derivative | 37 | (14) | 78 | (24)
S&P put options and futures |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Gain (Loss) on Derivative | (100) | (57) | (122) | (169)
Other derivative instruments |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Gain (Loss) on Derivative | (8) | (5) | 2 | (4)
Fixed Maturities [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
OTTI on fixed maturities, gross | (14) | (5) | (19) | (16)
OTTI on fixed maturities recognized in OCI (pre-tax) | 3 | 0 | 3 | 1
OTTI on fixed maturities, net | (11) | (5) | (16) | (15)
Gross realized gains excluding OTTI | 64 | 30 | 229 | 109
Gross realized losses excluding OTTI | (91) | (19) | (355) | (77)
Total fixed maturities | (38) | 6 | (142) | 17
Equity Securities [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Cost-method Investments, Other than Temporary Impairment | 0 | (1) | 0 | (9)
Equity Securities, Gross realized gains excluding OTTI | 48 | 6 | 63 | 21
Equity Securities, Gross realized losses excluding OTTI | (13) | (1) | (41) | (2)
Cost-method Investments, Realized Gain (Loss) | 35 | 4 | 22 | 10
Other Investments [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Cost-method Investments, Other than Temporary Impairment | 0 | (2) | 0 | (11)
Cost-method Investments, Realized Gain (Loss) | 5 | 0 | 23 | 0
Other | $ (5) | $ (11) | $ (61) | $ (10)

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