The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date.

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Liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims. This includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims.

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Amount, after valuation allowance, recoverable under reinsurance contracts for losses reported to the ceding insurer but not yet paid and amounts expected for incurred losses and settlement expenses, which have not yet been reported to the ceding insurer.

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Amount, after reinsurance, of paid claims and allocated claim adjustment expense used in claims development for short-duration insurance contracts. Excludes unallocated claim adjustment expense.

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Undiscounted amount, after reinsurance, of incurred claims and allocated claim adjustment expense used in claims development for short-duration insurance contracts. Excludes unallocated claim adjustment expense.

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Amount of reconciling item for the reconciliation of the liability in the disclosure of claims development (in excess of) less than the liability for unpaid claims and claims adjustment expense for short-duration insurance contracts, classified as other.

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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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Medical Claims Payable (Reconciliation Of The Claims Development To The Claims Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 239,548
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	228,459
Net medical claims payable, end of year	11,089
Ceded medical claims payable, end of year	46	$ 33	$ 34	$ 105
Insurance lines other than short duration	224
Total gross medical claims payable, end of year	11,359	8,842
Commercial and Specialty Business Segment [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	77,213
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	73,932
Net medical claims payable, end of year	3,281
Ceded medical claims payable, end of year	13	14	10	78
Total gross medical claims payable, end of year	3,294
Government Business Segment [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	160,849
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	153,236
Net medical claims payable, end of year	7,613
Ceded medical claims payable, end of year	33	19	$ 24	$ 27
Insurance lines other than short duration	224
Total gross medical claims payable, end of year	7,870
Other Segment [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	1,486
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	1,291
Net medical claims payable, end of year	195
Ceded medical claims payable, end of year	0	$ 0
Insurance lines other than short duration	0
Total gross medical claims payable, end of year	$ 195