Contingencies And Commitments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Proceeds from sales leaseback transaction	$ 62	$ 85	$ 47
Total rental expense on operating leases	43	44	$ 42
Total accumulated amortization related to sales leaseback transaction	101	92
Loss contingency accrual, insurance-related assessment, premium tax offset	(16)	$ (9)
Football Stadium Naming Rights Commitment [Member]
Loss Contingencies [Line Items]
Amount of commitment, total	$ 140
Time period of commitment	20 years
Approximate Amount Of Commitment Per Year	$ 7
Variable Annuity Product Concentration Risk [Member] \| Variable Annuity Deposits Total [Member]
Loss Contingencies [Line Items]
Concentration risk, percentage	14.00%	21.00%	18.00%
Variable Annuity Product Concentration Risk [Member] \| Variable Annuity Account Values Total [Member]
Loss Contingencies [Line Items]
Concentration risk, percentage	40.00%	41.00%	42.00%
Fund Choice Concentration Risk [Member] \| Variable Annuity Deposits Total [Member]
Loss Contingencies [Line Items]
Concentration risk, percentage	20.00%	23.00%	20.00%
Fund Choice Concentration Risk [Member] \| Variable Annuity Account Values Total [Member]
Loss Contingencies [Line Items]
Concentration risk, percentage	47.00%	47.00%	48.00%
Maximum [Member] \| Pending Litigation [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate	$ 50

The approximate amount the entity expects to spend per year under the long-term purchase commitment.

No definition available.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

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Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

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The minimum amount the entity agreed to spend under the long-term purchase commitment.

+ References

No definition available.

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Period covered by the long-term purchase commitment, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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The amount of insurance-related assessment liability that is expected to be recovered through a premium tax offset based on current laws applied to in-force policies.

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Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

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The accumulated depreciation and amortization related to the asset(s) sold in connection with the property sold to another party and leased back to the seller.

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Amount of cash inflow before closing and debt issuance costs received by a seller-lessee in a sale-leaseback recognized in financing activities.

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