Guaranteed Benefit Features (Summary Of Guaranteed Death Benefit Liabilities) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Guaranteed Benefit Features [Abstract]
Balance as of beginning-of-year	$ 100	$ 110
Changes in reserves	18	4
Benefits paid	(11)	(14)
Balance as of end-of-period	$ 107	$ 100

Amount of cash outflow to policyholders and contract holders for guaranteed minimum benefit payments.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 17
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3367-108585

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=6588021&loc=d3e7104-158389

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 80
-Section 50
-Paragraph 1
-Subparagraph (d)(4)
-URI http://asc.fasb.org/extlink&oid=6484115&loc=d3e19393-158473

Name:	us-gaap_LiabilitiesForGuaranteesOnLongDurationContractsPaymentForBenefits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration