Investments (Details 14) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Carrying value of non-impaired mortgage loans, summarized by debt service coverage ratio distribution
Total mortgage loans	$ 4,188	$ 4,721
Mortgage loans, non-impaired
Carrying value of non-impaired mortgage loans, summarized by debt service coverage ratio distribution
Fixed rate mortgage loans	4,151	4,561
Variable rate mortgage loans	21	79
Total mortgage loans	4,172	4,640
Net carrying value of impaired mortgage loans
Impaired mortgage loans with a valuation allowance	16	81
Total impaired mortgage loans	16	81
Valuation allowance on impaired mortgage loans	8	21	42
Rollforward of the valuation allowance on impaired mortgage loans
Valuation allowance on impaired mortgage loans, beginning balance	21	42	63
Net decrease in valuation allowance	(5)	(11)	(5)
Charge offs	(8)	(8)	(16)
Mortgage loans classified as held for sale		(2)
Valuation allowance on impaired mortgage loans, ending balance	8	21	42
Mortgage loans, non-impaired \| Below 1.0
Carrying value of non-impaired mortgage loans, summarized by debt service coverage ratio distribution
Fixed rate mortgage loans	110	153
Total mortgage loans	110	153
Mortgage loans, non-impaired \| 1.0 - 1.25
Carrying value of non-impaired mortgage loans, summarized by debt service coverage ratio distribution
Fixed rate mortgage loans	424	613
Total mortgage loans	424	613
Mortgage loans, non-impaired \| 1.26 - 1.50
Carrying value of non-impaired mortgage loans, summarized by debt service coverage ratio distribution
Fixed rate mortgage loans	1,167	1,233
Variable rate mortgage loans	1	2
Total mortgage loans	1,168	1,235
Mortgage loans, non-impaired \| Above 1.50
Carrying value of non-impaired mortgage loans, summarized by debt service coverage ratio distribution
Fixed rate mortgage loans	2,450	2,562
Variable rate mortgage loans	20	77
Total mortgage loans	2,470	2,639
Mortgage loans
Average carrying value and interest income recognized on impaired mortgage loans
Average impaired mortgage loans	$ 27	$ 88	$ 202

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

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

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The amount of financing receivables reclassified to held for sale during the reporting period.

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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 a related allowance for credit losses.

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Amount of loan with fixed 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 expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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