Investments (Available-For-Sale Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Debt Maturities, Amortized Cost
Amortized cost	$ 87,240	$ 84,747
Available-for-sale Securities, Debt Maturities, Fair Value
Fair Value	95,086	89,488
Fixed maturity AFS securities [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost
Amortized cost	86,993	84,487
Available-for-sale Securities, Debt Maturities, Fair Value
Fair Value	94,840	$ 89,213
Fixed maturity AFS securities other than structured securities [Member] \| Fixed maturity AFS securities [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost
Due in one year or less	3,214
Due after one year through five years	18,154
Due after five years through ten years	17,044
Due after ten years	42,958
Amortized cost	81,370
Available-for-sale Securities, Debt Maturities, Fair Value
Due in one year or less	3,252
Due after one year through five years	18,801
Due after five years through ten years	17,717
Due after ten years	49,223
Fair Value	88,993
Structured securities [Member] \| Fixed maturity AFS securities [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost
Amortized cost	5,623
Available-for-sale Securities, Debt Maturities, Fair Value
Fair Value	$ 5,847

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing after the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing after the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the next fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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