v3.8.0.1

Certain Long-Duration Contracts with Guarantees (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Annuity Contracts | Market Value Adjusted
Net Amount at Risk by Product and Guarantee [Line Items]
General Account Investment Option	$ 8,308	$ 8,566

X

- Definition

Value of the general accounts corresponding to the specified product, guarantee type and subset of the guarantee.

+ References

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

+ Details

Name:	us-gaap_NetAmountAtRiskByProductAndGuaranteeGeneralAccountValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_NetAmountAtRiskByProductAndGuaranteeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_ProductOrServiceAxis=us-gaap_VariableAnnuityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_MarketValueGuaranteeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: