| **Stock-based Compensation - (Tables)**                                                            | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
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| **Disclosure of Compensation Related Costs, Share-based Payments [Abstract]**                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| Summary of stock-based compensation costs                                                          | Stock-based compensation costs are as follows for the years ended December 31: 2015 2014 2013Stock-based compensation cost$120 $122 $115Tax benefit(28) (26) (24)Stock-based compensation cost, net of tax$92 $96 $91                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| Weighted average assumptions used in the option pricing model for options granted                  | The fair value of each stock option granted is estimated using the Black-Scholes option pricing model.  The following table presents the weighted average assumptions used in the option pricing model for options granted.  The expected life of the options represents the period of time the options are expected to be outstanding.  The expected life is based on our historical exercise trends and post-vest termination data incorporated into a forward-looking stock price model.  The expected volatility is based on our implied volatility, which is the volatility forecast that is implied by the prices of actively traded options to purchase our stock observed in the market.  The risk-free interest rate is based on the observed U.S. Treasury yield curve in effect at the time the options were granted.  The dividend yield is based on our history of dividend payouts.  2014 2013Expected life (years) 4.6 5.2Risk-free interest rate 1.5% 1.3%Volatility 31.9% 36.0%Dividend yield 1.0% 1.3%Weighted average fair value per share at grant date $16.81 $13.79 |
| Summary of stock options outstanding and related information                                       | The following table presents the changes in stock options outstanding and related information (in thousands, except per option prices): Number ofOptions Weighted AverageExercise PricePer OptionOutstanding at December 31, 2014 9,737   $53.80 Granted —   — Exercised (873)   44.25 Forfeited (124)   53.90 Expired (138)   67.85 Outstanding at December 31, 2015 8,602   $54.56 Exercisable at December 31, 2015 7,363   $54.46                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Summary of restricted stock awards                                                                 | The following table presents the combined changes of RSAs and RSUs and related information (in thousands, except per award/unit prices): Number ofAwards and Units Weighted AverageGrant Date FairValue Per Award/UnitUnvested balance at December 31, 20142,732 $57.88Granted2,314 57.37Vested(1,299) 55.09Forfeited(391) 54.62Unvested balance at December 31, 20153,356 $58.99                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Assumptions used in estimating fair value of shares granted under the employee stock purchase plan | Compensation cost for the years ended December 31, was calculated using the Black-Scholes option pricing model with the following assumptions: 2015 2014 2013Expected life (years)0.5 0.5 0.5Risk-free interest rate0.1% 0.03% 0.1%Volatility30.9% 24.7% 30.3%Dividend yield1.2% 1.0% 1.4%Fair value per share of the 15% cash discount$8.79 $9.72 $6.45Fair value per share of the look-back provision4.97 4.39 3.58Total weighted average fair value per share at grant date$13.76 $14.11 $10.03                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |

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| - Definition
Tabular disclosure of the allocation of equity-based compensation costs to a given line item on the balance sheet and income statement for the period. This may include the reporting line for the costs and the amount capitalized and expensed.
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| - Definition
Tabular disclosure of the number and weighted-average exercise prices (or conversion ratios) for share options (or share units) that were outstanding at the beginning and end of the year, vested and expected to vest, exercisable or convertible at the end of the year, and the number of share options or share units that were granted, exercised or converted, forfeited, and expired during the year.
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| - Definition
Tabular disclosure of the significant assumptions used during the year to estimate the fair value of employee stock purchase plans, including, but not limited to: (a) expected term, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions.
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| - Definition
Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions.
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| - Definition
Disclosure of the number and weighted-average grant date fair value for restricted stock and restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock and restricted stock units that were granted, vested, or forfeited during the year.
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No definition available.
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