Reinsurance - Life Insurance Ceded Business (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Reinsurance for Insurance Companies, by Product Segment [Line Items]
Insurance losses and contract holders' benefits	$ 883	$ 854	$ 1,737	$ 1,707
Life Insurance Segment
Reinsurance for Insurance Companies, by Product Segment [Line Items]
Direct earned premiums	81	77	158	151
Ceded earned premiums	(17)	(17)	(34)	(34)
Earned premiums	64	60	124	117
Direct contract holders' benefits incurred	70	87	146	163
Ceded contract holders' benefits incurred	(8)	(27)	(21)	(38)
Insurance losses and contract holders' benefits	$ 62	$ 60	$ 125	$ 125

Amount of earned premiums ceded to other entities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.1)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount, before effect of policies assumed or ceded, of expense related to provision for policy benefits and costs incurred.

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Amount, after premiums ceded to other entities and premiums assumed by the entity, of life premiums earned.

+ References

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Amount of reduction of provision for policy benefits and costs incurred for policies ceded.

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