Reinsurance - GMIB Reinsurers (Details) - Guaranteed Minimum Income Benefit [Member] $ in Millions	6 Months Ended
Jun. 30, 2018 USD ($) Reinsurers	Dec. 31, 2017 USD ($)
Ceded Credit Risk [Line Items]
Annuitization election period	30 days
Number of external reinsurers \| Reinsurers	3
GMIB Assets	$ 684	$ 777
Berkshire [Member]
Ceded Credit Risk [Line Items]
GMIB Assets	$ 320	359
Berkshire [Member] \| Ceded Credit Risk Secured [Member] \| GMIB Assets [Member]
Ceded Credit Risk [Line Items]
Concentration percentage	100.00%
Sun Life Assurance Company Of Canada [Member]
Ceded Credit Risk [Line Items]
GMIB Assets	$ 191	221
Liberty Re (Bermuda) Ltd. [Member]
Ceded Credit Risk [Line Items]
GMIB Assets	$ 173	$ 197
Liberty Re (Bermuda) Ltd. [Member] \| Ceded Credit Risk Secured [Member] \| GMIB Assets [Member]
Ceded Credit Risk [Line Items]
Concentration percentage	100.00%

The period of time prior to a policy anniversary when an annuitization election must occur.

No definition available.

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- Definition

The number of external reinsurers underwriting credit risk ceded by the Company.

+ References

No definition available.

+ Details

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- 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

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

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- Details

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- Details

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