Investments (Allowance For Credit Loss Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Fixed Maturity Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Additions for securities for which no previous expected credit losses were recognized	$ 1	$ 62
Allowance for credit loss, securities sold	(5)	(13)
Increase (decrease) to the allowance for credit losses on securities	(8)	(37)
Fixed Maturity Securities, Available-for-sale, Allowance for Credit Loss	12	12	$ 24	$ 0
Corporate Securities [Member]
Fixed Maturity Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Additions for securities for which no previous expected credit losses were recognized	1	61
Allowance for credit loss, securities sold	(5)	(13)
Increase (decrease) to the allowance for credit losses on securities	(8)	(37)
Fixed Maturity Securities, Available-for-sale, Allowance for Credit Loss	11	11	23	0
Foreign Government Securities [Member]
Fixed Maturity Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Additions for securities for which no previous expected credit losses were recognized	0	1
Allowance for credit loss, securities sold	0	0
Increase (decrease) to the allowance for credit losses on securities	0	0
Fixed Maturity Securities, Available-for-sale, Allowance for Credit Loss	$ 1	$ 1	$ 1	$ 0

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922900-210455

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922900-210455

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

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Amount of expense for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), for which no credit loss was previously recorded.

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Amount of increase (decrease) in allowance for credit loss of 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 326
-SubTopic 30
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922900-210455

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

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