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Summary of significant accounting policies (Narrative) (Detail) - USD ($) $ in Millions | 6 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Jul. 01, 2022 | Jan. 01, 2021
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Deferred Marketing Costs, Amortization Period |  | 10 years |  |  |  |
Deferred Advertising Costs | $ 243 | $ 243 | $ 189 |  |  |
Deferred Policy Acquisition Costs, Amortization Expense |  | $ 7,392 | 6,918 | $ 6,547 |  |
Recoverable from unrated reinsurers, ceded reserve, default factor (percent) |  | 34.00% |  |  |  |
Percentage of fair value of loaned securities |  | 102.00% |  |  |  |
Quality assessment threshold used in goodwill impairment testing |  | 50.00% |  |  |  |
Property, Plant and Equipment, Net | 2,400 | $ 2,400 | 2,000 |  |  |
Net operating results of ESIS included within Administrative expenses |  | 12 | 25 | 18 |  |
Cigna integration expenses |  | 48 | 0 | 0 |  |
Net income |  | 5,313 | 8,539 | 3,533 |  |
Comprehensive Income (Loss), Net of Tax, Attributable to Parent |  | (5,230) | 6,020 | 5,783 |  |
Deposit liabilities included in Deposit liabilities | 70 | 70 | 74 |  |  |
Retained earnings | 48,334 | 48,334 | 47,365 |  |  |
Accumulated other comprehensive income | (10,193) | (10,193) | 350 |  |  |
Stockholders' Equity | (50,540) | (50,540) | (59,714) | (59,441) |  |
Deposit Assets | 96 | 96 | 101 |  |  |
Accounting Standards Update 2018-12 | Cumulative Effect, Period of Adoption, Adjustment [Member] |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Stockholders' Equity |  |  |  |  |  | $ 1,800
Cigna's Life Insurance Business in Asian Markets |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Net income | $ 148 |  |  |  |  |
Stockholders' Equity |  |  |  |  | $ (5,359) |
Cigna's Life Insurance Business in Asian Markets | Debt Securities [Member] |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Assets, Fair Value Adjustment |  | $ 211 |  |  |  |
Minimum |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Reinsurance Premiums, Amortization Period |  | 1 year |  |  |  |
Debt Securities, Held-to-Maturity, Accrued Interest, Threshold Period, Writeoff | 30 days | 30 days |  |  |  |
Liability for Future Policy Benefits, Interest Rate | 1.00% | 1.00% |  |  |  |
Maximum |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Reinsurance Premiums, Amortization Period |  | 3 years |  |  |  |
Affiliated notional cash pooling program | $ 300 | $ 300 |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 25 years |  |  |  |
Debt Securities, Held-to-Maturity, Accrued Interest, Threshold Period, Writeoff | 45 days | 45 days |  |  |  |
Liability for Future Policy Benefits, Interest Rate | 9.00% | 9.00% |  |  |  |
Selling and Marketing Expense [Member] |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Deferred Policy Acquisition Costs, Amortization Expense |  | $ 121 | 85 | $ 99 |  |
Fair Value Adjustment to Acquired Loss Reserves [Member] | The Chubb Corporation [Member] |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Balance of FV adjustment on Unpaid Losses and Loss Expenses | $ 74 | 74 | $ 90 |  |  |
Software Development [Member] |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Property, Plant and Equipment, Net | 1,600 | $ 1,600 |  |  |  |
Property, Plant and Equipment, Useful Life |  | 15 years |  |  |  |
Software Development [Member] | Minimum |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  | 3 years |  |  |  |
Software Development [Member] | Maximum |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  | 5 years |  |  |  |
Building [Member] |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Property, Plant and Equipment, Net | $ 253 | $ 253 |  |  |  |
Building [Member] | Maximum |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  | 40 years |  |  |  |

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