Investments - Carrying Value of Non-impaired Fixed Rate and Variable Rate Mortgage Loans (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Carrying value of non-impaired fixed rate and variable rate mortgage loans by debt service coverage ratio distribution
Total	$ 4,034	$ 3,995
Net carrying value of impaired mortgage loans
Impaired mortgage loans with a valuation allowance	4	4
Impaired mortgage loans without a valuation allowance	0	0
Total impaired mortgage loans	4	4
Valuation allowance on impaired mortgage loans	3	3
Non-impaired mortgage loans
Carrying value of non-impaired fixed rate and variable rate mortgage loans by debt service coverage ratio distribution
Fixed rate mortgage loans	3,972	3,934
Variable rate mortgage loans	58	57
Total	4,030	3,991
Non-impaired mortgage loans \| Below 1.0
Carrying value of non-impaired fixed rate and variable rate mortgage loans by debt service coverage ratio distribution
Fixed rate mortgage loans	22	6
Variable rate mortgage loans	16	15
Total	38	21
Non-impaired mortgage loans \| 1.0 - 1.25
Carrying value of non-impaired fixed rate and variable rate mortgage loans by debt service coverage ratio distribution
Fixed rate mortgage loans	203	221
Variable rate mortgage loans	0	0
Total	203	221
Non-impaired mortgage loans \| 1.26 - 1.50
Carrying value of non-impaired fixed rate and variable rate mortgage loans by debt service coverage ratio distribution
Fixed rate mortgage loans	1,042	1,048
Variable rate mortgage loans	0	0
Total	1,042	1,048
Non-impaired mortgage loans \| Above 1.50
Carrying value of non-impaired fixed rate and variable rate mortgage loans by debt service coverage ratio distribution
Fixed rate mortgage loans	2,705	2,659
Variable rate mortgage loans	42	42
Total	$ 2,747	$ 2,701

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A valuation allowance for financing receivables that are expected to be uncollectible.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
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Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

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Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

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Amount of loan with fixed rate of interest.

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-Publisher FASB
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Amount of loan with variable or adjustable rate of interest.

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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.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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