Investments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Net Investment Income [Line Items]
Reduction of net unrealized gains on investments included in AOCI due to shadow adjustments	$ 1,186	$ 1,186	$ 1,411
Derivative, notional amount	161	161	167
Derivative fair value	4	4
Derivative fair value			$ (3)
Future capital call commitments for limited partnership investments	551	551
Mortgage loan commitments	15	15
Commitments to purchase or fund privately placed debt securities	272	272
Commitments to sell various privately placed debt securities	111	111
Common Stock
Net Investment Income [Line Items]
Net investment income (losses)	2	1
Preferred stock
Net Investment Income [Line Items]
Net investment income (losses)	$ (10)	$ (25)

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Commitments To Sell Various Privately Placed Debt Securities

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Future capital call commitments to limited partnerships for which we would receive an ownership interest.

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Mortgage loan commitments, representing signed loan applications received and accepted.

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Reduction of net unrealized gains on investments included in AOCI due to shadow adjustments

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Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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