Investments (Net Investment Gains Losses - Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Gains (losses) from foreign currency transactions	$ 14	$ 65

Amount before tax of foreign currency transaction realized gain (loss) recognized in the income statement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 45
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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