|**Share-Based Associate Compensation Plans (Tables)**                              | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
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|**Share-based Compensation Arrangement by Share-based Payment Award [Line Items]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Stock Option Information                                                           | Below is a summary of option information for the year2017:(Dollars in millions, except exercise price. Shares in thousands)SharesWeighted-averageexercise priceAggregateintrinsicvalueWeighted-averageremaining contractuallifeOutstanding option shares at January 1, 20173,012$42.12Granted70670.70Exercised(527)38.33Forfeited or expired(125)47.07Outstanding option shares at December 31, 20173,06649.14$795.61 yearsOptions exercisable at end of period2,072$40.69$714.13 years
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|(Dollars in millions, except exercise price. Shares in thousands)                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Outstanding option shares at January 1, 2017                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Granted                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Exercised                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Forfeited or expired                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Outstanding option shares at December 31, 2017                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
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|Options exercisable at end of period                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
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|Restricted Stock Unit Information                                                  | Below is a summary of service-based and performance-based share information, assuming a target payout for performance-based shares, for the year2017:(Shares in thousands)Service-basedsharesWeighted-average grantdate fair valuePerformance-basedsharesWeighted-average grantdate fair valueNonvested at January 1, 2017888$48.59236$49.64Granted29265.165743.26Vested(311)43.05(87)36.73Forfeited or canceled(26)55.59——Nonvested at December 31, 201784356.1620653.35              
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|(Shares in thousands)                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Nonvested at January 1, 2017                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Granted                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Vested                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Forfeited or canceled                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Nonvested at December 31, 2017                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
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|Stock Options                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|**Share-based Compensation Arrangement by Share-based Payment Award [Line Items]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Assumptions Used In Option Grants Issued                                           | The following weighted average assumptions were used in determining fair value for option grants issued:201720162015Weighted-average expected term8 years8 years8-9 yearsExpected volatility16.95%24.88-25.75%25.04-26.15%Dividend yield2.83%2.58-3.12%3.52%Risk-free rates2.33%1.44-1.60%1.94-2.01%Weighted-average fair value of options granted during the period$10.79$13.21$11.15                                                                                                 
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|Weighted-average expected term                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Expected volatility                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Dividend yield                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Risk-free rates                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Weighted-average fair value of options granted during the period                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
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|Performance Based Shares                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|**Share-based Compensation Arrangement by Share-based Payment Award [Line Items]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Assumptions Used In Option Grants Issued                                           | The following assumptions were used in determining fair value for performance-based grants issued:201720162015Expected term2.89 years2.44-2.88 years2.88 yearsExpected volatility15.75-28.35%15.42-33.64%13.78-34.69%Dividend yield2.83%2.58-3.12%3.52%Risk-free rates1.44%0.77-0.87%0.99%                                                                                                                                                                                             
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|Expected term                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Expected volatility                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Dividend yield                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Risk-free rates                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
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X- DefinitionTabular disclosure of the number and weighted-average grant date fair value for restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock units that were granted, vested, or forfeited during the year.
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