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

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

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Amount of direct write-downs of financing receivables charged against the allowance.

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Average 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 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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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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Amount of increase (decrease) in valuation and qualifying accounts and reserves.

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Investments - Mortgage loans other (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017
Carrying value of non-impaired fixed rate and variable rate mortgage loans by debt service coverage ratio distribution
Total				$ 3,995	$ 3,876
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	$ 3	3	3
Rollforward of the valuation allowance on impaired mortgage loans
Beginning balance	3	3	3
Net increase in valuation allowance	0	1	0
Charge offs	0	(1)	0
Ending balance	3	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				3,934	3,844
Variable rate mortgage loans				57	28
Total				3,991	3,872
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				6	3
Variable rate mortgage loans				15	0
Total				21	3
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				221	326
Variable rate mortgage loans				0	0
Total				221	326
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				1,048	1,033
Variable rate mortgage loans				0	15
Total				1,048	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				2,659	2,482
Variable rate mortgage loans				42	13
Total				$ 2,701	$ 2,495
Mortgage loans
Average carrying value and interest income recognized on impaired mortgage loans
Average balance impaired mortgage loans	$ 4	$ 7	$ 6