Deferred Policy Acquisition Costs, Value of Business Acquired and Other Policy-Related Intangibles (Estimated Future Amortization) (Details) $ in Millions	Dec. 31, 2017 USD ($)
Estimated future amortization expense allocated to other expenses for VOBA [Abstract]
VOBA 2018	$ 98
VOBA 2019	84
VOBA 2020	62
VOBA 2021	53
VOBA 2022	46
Distribution Rights [Member]
Value of Distribution Agreements and Customer Relationships Acquired [Abstract]
VODA 2018	14
VODA 2019	13
VODA 2020	12
VODA 2021	10
VODA 2022	$ 9

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during 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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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during 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 of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fourth 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 of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the third 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 of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the second 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 of amortization expense expected to be recognized during fifth fiscal year following latest fiscal year for present value of future profits of insurance contract acquired in business combination.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Publisher FASB
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-Section 50
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Amount of amortization expense expected to be recognized during fourth fiscal year following latest fiscal year for present value of future profits of insurance contract acquired in business combination.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of amortization expense expected to be recognized during next fiscal year following latest fiscal year for present value of future profits of insurance contract acquired in business combination.

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Amount of amortization expense expected to be recognized during third fiscal year following latest fiscal year for present value of future profits of insurance contract acquired in business combination.

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Amount of amortization expense expected to be recognized during second fiscal year following latest fiscal year for present value of future profits of insurance contract acquired in business combination.

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