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
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://www.xbrl.org/2003/role/presentationRef
-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=6879938&loc=d3e572229-122910

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- Definition

The amount of mortgage loans on real estate which were foreclosed on during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29.6)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

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- Definition

Total amount of new mortgage loans on real estate during the reporting period.

+ 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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