Investments - Mortgage Loans (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($)
Scheduled Mortgage Loan Principal Repayments [Abstract]
Mortgage loans	$ 1,361
Commercial Real Estate
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
New mortgage loans	4
Mortgage loans fully repaid	27
Mortgage loans foreclosed	0
Scheduled Mortgage Loan Principal Repayments [Abstract]
2019	145
2020	109
2021	269
2022	228
2023	83
Thereafter	527
Mortgage loans	1,361
Commercial Real Estate \| Category 1
Scheduled Mortgage Loan Principal Repayments [Abstract]
Mortgage loans	42
Commercial Real Estate \| Category 2 to 4
Scheduled Mortgage Loan Principal Repayments [Abstract]
Mortgage loans	1,301
Commercial Real Estate \| Categories 5 and 6
Scheduled Mortgage Loan Principal Repayments [Abstract]
Mortgage loans	18
Commercial Real Estate \| Category 7
Scheduled Mortgage Loan Principal Repayments [Abstract]
Mortgage loans	$ 0

Mortgage Loans On Real Estate Collections Of Principal After Year Five

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- Definition

Mortgage Loans On Real Estate Collections Of Principal In Next Twelve Months

+ References

No definition available.

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- Definition

Mortgage Loans On Real Estate Collections Of Principal In Year Five

+ References

No definition available.

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- Definition

Mortgage Loans On Real Estate Collections Of Principal In Year Four

+ References

No definition available.

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- Definition

Mortgage Loans On Real Estate Collections Of Principal In Year Three

+ References

No definition available.

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- Definition

Mortgage Loans On Real Estate Collections Of Principal In Year Two

+ References

No definition available.

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- Definition

Pertains to amount of mortgage loans fully repaid.

+ References

No definition available.

+ Details

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- Definition

The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(c))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

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- Definition

Amount of decrease in investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, from foreclosure.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Footnote 6))
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

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- Definition

Amount of increase in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, from new investment.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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