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Claim and Claim Adjustment Expense Reserves (Reconciliation of claim and claim adjustment expense reserves) (Details) - USD ($) $ in Millions | 9 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020 | Dec. 31, 2019
Reserves, beginning of year: |  |  |  |
Gross | $ 22,706 | $ 21,720 |  |
Ceded | 4,005 | 3,835 |  |
Net reserves, beginning of year | 18,701 | 17,885 |  |
Reduction of net reserves due to Excess Workers' Compensation Loss Portfolio Transfer |  |  | $ (632) | $ 0
Net incurred claim and claim adjustment expenses: |  |  |  |
Provision for insured events of current year | 4,474 | 4,425 |  |
Increase (decrease) in provision for insured events of prior years | (130) | (68) |  |
Amortization of discount | 137 | 143 |  |
Total net incurred | 4,481 | 4,500 |  |
Net payments attributable to: |  |  |  |
Current year events | (629) | (556) |  |
Prior year events | (2,874) | (3,285) |  |
Total net payments | (3,503) | (3,841) |  |
Foreign currency translation adjustment and other | (51) | 39 |  |
Net reserves, end of period | 18,996 | 18,583 |  |
Ceded reserves, end of period | 4,836 | 3,951 |  |
Gross reserves, end of period | $ 23,832 | $ 22,534 |  |

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- Definition Liability for Unpaid Claims and Claims Adjustment Expense Foreign CTA and other + References No definition available. + Details
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- Definition Liability for Unpaid Claims and Claims Adjustment Expense Incurred Claims Amortization of Discount + References No definition available. + Details
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- Definition Amount, after effects of reinsurance, of payments to settle claims incurred in the current period and related claims settlement costs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437 + Details
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- Definition Amount, after effects of reinsurance, of payments to settle claims incurred in prior periods and related claims settlement costs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437 + Details
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- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(13)(a)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (cc) -URI http://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437 + Details
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- Definition Sum of adjustments to the estimated reserve for unpaid claims and claims adjustment expense. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437 + Details
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