| **Stock-Based Compensation**                                                  | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
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| **Disclosure of Compensation Related Costs, Share-based Payments [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| Stock-Based Compensation [Text Block]                                         | Note K. Stock-Based Compensation The CNAF Incentive Compensation Plan (the Plan), as amended and restated on January 1, 2010, authorizes the grant of stock-based compensation to certain management personnel for up to 6 million shares of CNAF's common stock.  The Plan currently provides for awards of stock options, stock appreciation rights (SARs), restricted shares, performance-based restricted share units (RSUs) and performance share units.  The number of shares available for the granting of stock-based compensation under the Plan as of December 31, 2014 was approximately 1.5 million.The Company recorded stock-based compensation expense related to the Plan of $11 million, $10 million and $9 million for the years ended December 31, 2014, 2013 and 2012.  The related income tax benefit recognized was $4 million, $3 million and $3 million for the years ended December 31, 2014, 2013, and 2012. The compensation cost related to non-vested awards not yet recognized was $13 million, and the weighted average period over which it is expected to be recognized is 1.7 years at December 31, 2014.Equity based compensation that is not fully vested prior to termination is generally forfeited upon termination, except as otherwise provided by contractual obligations.  In addition, any such compensation that vested prior to termination is generally canceled immediately, except in cases of retirement, death or disability, and as otherwise provided by contractual obligations.Share AwardsThe fair value of share awards is based on the market value of the Company's common stock as of the date of grant. Share awards currently granted under the Plan include restricted shares, performance-based RSUs and performance share units.  Generally, restricted shares vest ratably over a four-year service period following the date of grant.  Performance-based RSUs generally become payable within a range of 0% to 100% of the number of shares initially granted based upon the attainment of specific annual performance goals and vest ratably over a four-year service period following the date of grant.  Performance share units become payable within a range of 0% to 200% of the number of shares initially granted based upon the attainment of specific performance goals achieved over a three year period. The following table presents activity for non-vested restricted shares, performance-based RSUs and performance share units under the Plan in 2014.Number of AwardsWeighted-Average Grant Date Fair ValueBalance at January 1, 2014847,674$29.61Awards granted261,27341.01Awards vested(156,332)28.42Awards forfeited, canceled or expired(91,002)32.09Performance-based adjustment52,56828.50Balance at December 31, 2014914,181$32.76Stock Options and SARsThe exercise price of all stock options and SARs granted is based on the market value of the Company's common stock as of the date of grant.  Stock options and SARs generally vest ratably over a four-year service period following date of grant and have a maximum term of ten years.The fair value of granted stock options and SARs was estimated at the grant date using the Black-Scholes option-pricing model.  The Black-Scholes model incorporates a risk free rate of return and various assumptions regarding the underlying common stock and the expected life of the securities granted.  Different interest rates and assumptions were used for each grant, as appropriate based on date of grant.There were no stock options or SARs granted for the years ended December 31, 2014 and 2013.  For the year ended December 31, 2012 there were 10 thousand awards granted.  As of December 31, 2014, there were approximately 1 million awards outstanding, fully vested and expected to vest and exercisable.  The fair value of awards vested was $1 million for the years ended December 31, 2014, 2013 and 2012. |

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| - Definition
The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.
+ References
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