Reinsurance Level 4 Reinsurance Recoverable (Details) - USD ($)	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverable for Paid Claims and Claims Adjustments	$ 161,000,000	$ 170,000,000
Reinsurance Recoverables on Unpaid Losses, Gross	2,449,000,000	2,662,000,000
Premiums Receivable, Allowance for Doubtful Accounts	(165,000,000)	(266,000,000)
Reinsurance Recoverables, Including Reinsurance Premium Paid	23,311,000,000	23,189,000,000
Fair Value, Concentration of Risk, Investments	0	0
Asbestos and Environmental [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	1,655,000,000
Reinsurance Recoverables, Including Reinsurance Premium Paid	1,500,000,000
Property, Liability and Casualty Insurance Product Line [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	5,088,000,000
Gross reinsurance recoverable	2,538,000,000	2,781,000,000
Reinsurance Recoverables, Including Reinsurance Premium Paid	2,373,000,000	2,515,000,000
Life Insurance Product Line [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	20,938,000,000	20,674,000,000
Life Insurance Product Line [Member] \| Continuing Operations [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	1,209,000,000	1,305,000,000
P&C Runoff Subsidiaries [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverable for Paid and Unpaid Claims and Claims Adjustments	178,000,000
Retirement Plans and Individual Life Businesses [Member] \| Life Insurance Product Line [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	19,729,000,000	19,369,000,000
Retirement Plans [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	8,600,000,000	8,600,000,000
Individual Life [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverables, Including Reinsurance Premium Paid	11,100,000,000	10,800,000,000
Reinsurance Recoverable [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Fair Value, Concentration of Risk, Investments	0
Premium [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Payments for Reinsurance	650,000,000
Reinsurance Payable	650,000,000
Property and Casualty Insurance Subsidiaries [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Recoverables on Paid Losses, Gross	$ 89,000,000	$ 119,000,000

This item represents disclosure of all significant concentrations of credit risk or market risk arising from the subject financial instrument (as defined), whether from an individual counterparty or groups of counterparties.

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Cash payments made for reinsurance during the current period.

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The carrying value as of the balance sheet date of the estimated valuation allowance to reduce gross premiums receivable to net realizable value.

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Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

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Amount before valuation allowance of reinsurance recoverables for losses reported to the ceding insurer but not yet paid, and for amounts expected based upon statistical projections and other measures of incurred losses and loss settlement expenses which have not yet been reported to the ceding insurer.

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