| **Debt (Schedule of debt instruments) (Details) - USD ($)**           | Dec. 31, 2022   | Dec. 31, 2021 |
|-----------------------------------------------------------------------|-----------------|---------------|
| **Debt Instrument [Line Items]**                                      |            |          |
| Short term debt                                                       | $ 243,000,000   | $ 0           |
| Long term debt                                                        | 2,538,000,000   | 2,779,000,000 |
| Total debt                                                            | $ 2,781,000,000 | 2,779,000,000 |
| 3.950%, face amount of $550, due May 15, 2024                         |            |          |
| **Debt Instrument [Line Items]**                                      |            |          |
| Stated interest rate                                                  | 3.95%           |          |
| Face amount                                                           | $ 550,000,000   |          |
| Long term debt                                                        | $ 549,000,000   | 549,000,000   |
| 4.500%, face amount of $500, due March 1, 2026                        |            |          |
| **Debt Instrument [Line Items]**                                      |            |          |
| Stated interest rate                                                  | 4.50%           |          |
| Face amount                                                           | $ 500,000,000   |          |
| Long term debt                                                        | $ 499,000,000   | 499,000,000   |
| 3.450%, face amount of $500, due August 15, 2027                      |            |          |
| **Debt Instrument [Line Items]**                                      |            |          |
| Stated interest rate                                                  | 3.45%           |          |
| Face amount                                                           | $ 500,000,000   |          |
| Long term debt                                                        | $ 497,000,000   | 497,000,000   |
| 3.900%, face amount of $500, due May 1, 2029                          |            |          |
| **Debt Instrument [Line Items]**                                      |            |          |
| Stated interest rate                                                  | 3.90%           |          |
| Face amount                                                           | $ 500,000,000   |          |
| Long term debt                                                        | $ 497,000,000   | 496,000,000   |
| 2.050%, face amount of $500, due August 15, 2030                      |            |          |
| **Debt Instrument [Line Items]**                                      |            |          |
| Stated interest rate                                                  | 2.05%           |          |
| Face amount                                                           | $ 500,000,000   |          |
| Long term debt                                                        | 496,000,000     | 495,000,000   |
| Debenture of CNAF, 7.250%, face amount of $243, due November 15, 2023 |            |          |
| **Debt Instrument [Line Items]**                                      |            |          |
| Long term debt                                                        | $ 0             | 243,000,000   |
| Debenture of CNAF, 7.250%, face amount of $243, due November 15, 2023 |            |          |
| **Debt Instrument [Line Items]**                                      |            |          |
| Stated interest rate                                                  | 7.25%           |          |
| Face amount                                                           | $ 243,000,000   |          |
| Short term debt                                                       | $ 243,000,000   | $ 0           |

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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Face (par) amount of debt instrument at time of issuance.
+ References
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Contractual interest rate for funds borrowed, under the debt agreement.
+ References
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| - Definition
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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| - Definition
Represents the aggregate of total long-term debt, including current maturities and short-term debt.
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No definition available.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt classified as noncurrent. Excludes lease obligation.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.
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