|**Stock-Based Compensation**                   | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
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|**Share-based Payment Arrangement [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|Stock-Based Compensation                       | Stock-Based Compensation The current CNAF Incentive Compensation Plan (the Plan) authorizes the grant of stock-based compensation to certain management personnel for up to 16 million shares of CNAF common stock.  The Plan currently provides for awards of stock options, stock appreciation rights (SARs), restricted shares, restricted stock units (RSUs), performance-based RSUs and performance share units.  These grants to employees are not designed to be spring-loaded.  The number of shares available for the granting of stock-based compensation under the Plan as of December 31, 2021 was approximately 5.6 million.Substantially all of the Company's stock-based compensation is awarded under the Annual Performance Share Plan (PSP).  The PSP provides officers with an opportunity to earn an award based upon attainment of specific performance goals achieved over a one-year performance period.  Awards are granted in the form of performance share units at the beginning of each performance year and are generally subject to a two-year cliff vesting period after the Company’s annual performance has been determined.  The performance share units become payable within a range of 0% to 200% of the number of performance share units initially granted.Additionally, the Company may grant RSUs under the Plan in certain circumstances.  These awards generally vest over a one to three-year service period following the grant date.Stock-based compensation that is not fully vested prior to termination is generally forfeited upon termination, except in cases of retirement, death or disability, and as otherwise provided by contractual obligations. The fair value of stock-based compensation awards is based on the market value of the Company's common stock as of the date of grant, except for awards made to foreign participants, which is based on the current market value of the Company’s common stock.  Payments made under the PSP are made entirely in shares of common stock granted under the Plan, except for awards made to foreign participants, which are paid in cash.The Company recorded stock-based compensation expense related to the Plan of $32 million,$37 million and $34 million for the years ended December 31, 2021, 2020 and 2019.  The related income tax benefit recognized was $6 million, $6 million and $8 million for the years ended December 31, 2021, 2020 and2019.  The compensation cost not yet recognized was $41 million, and the weighted average period over which it is expected to be recognized is 1.7 years as of December 31, 2021.The total fair value of RSUs and performance shares that vested during the years ended December 31, 2021, 2020 and 2019 was $36 million, $35 million and $31 million, respectively.The weighted average grant date fair value for RSUs and performance shares granted during the years ended December 31, 2021, 2020 and 2019 was $45.82, $34.36 and $43.86, respectively.The following table presents activity for non-vested RSUs and performance share units under the Plan in 2021.Number of AwardsWeighted Average Grant Date Fair ValueBalance as of January 1, 20212,439,141$40.56Awards granted1,044,77245.82Awards vested(789,495)46.13Awards forfeited, canceled or expired(355,881)40.19Performance-based adjustment37,06143.70Balance as of December 31, 20212,375,59841.21
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|                                               | Number of Awards                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Balance as of January 1, 2021                  | 2,439,141                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Awards granted                                 | 1,044,772                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Awards vested                                  | (789,495)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Awards forfeited, canceled or expired          | (355,881)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Performance-based adjustment                   | 37,061                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Balance as of December 31, 2021                | 2,375,598                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  

X- DefinitionThe entire disclosure for share-based payment arrangement.
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