Investments (Available-For-Sale Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Available-for-sale Securities, Debt Maturities, Amortized Cost
Amortized cost	$ 90,083	$ 87,240
Available-for-sale Securities, Debt Maturities, Fair Value
Fair Value	93,060	95,086
Fixed Maturity AFS Securities [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost
Amortized cost	90,083	86,993
Available-for-sale Securities, Debt Maturities, Fair Value
Fair Value	93,060	$ 94,840
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	3,607
Due after one year through five years	18,525
Due after five years through ten years	17,025
Due after ten years	44,765
Amortized cost	83,922
Available-for-sale Securities, Debt Maturities, Fair Value
Due in one year or less	3,649
Due after one year through five years	18,658
Due after five years through ten years	17,013
Due after ten years	47,482
Fair Value	86,802
Structured securities [Member] \| Fixed Maturity AFS Securities [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost
Amortized cost	6,161
Available-for-sale Securities, Debt Maturities, Fair Value
Fair Value	$ 6,258

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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