Investments (Net realized investment gains (losses)) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fixed maturity securities:
Gross gains	$ 125	$ 168	$ 186
Gross losses	(131)	(164)	(64)
Net investment gains (losses) on fixed maturity securities	(6)	4	122
Equity securities	66	(74)	0
Derivatives	(11)	9	(4)
Short term investments and other	(20)	9	(25)
Net investment gains (losses)	$ 29	$ (52)	$ 93

Investments and Derivatives, Realized Gain (Loss)

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- Definition

Realized Gain (Loss) on Short Term Investments

+ References

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- References

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- Definition

Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27357-111563

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- Definition

Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27357-111563

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- Definition

Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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- Definition

Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714

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- Definition

The difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
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-Subparagraph (SX 210.9-04.13(h))
-URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260

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