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Incentive Plans (Fair Value of Option Award Estimated on Date of Grant using Black-Scholes Pricing Model) (Details) - Stock Options [Member] - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]      
Fair value per option grant   $ 12.84  
Assumptions      
Dividend yield   2.00%  
Expected volatility   29.00%  
Risk-free interest rate   1.62%  
Expected life 5 years 3 months 18 days 5 years 4 months 6 days  
Minimum [Member]      
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]      
Fair value per option grant $ 10.97   $ 15.81
Assumptions      
Dividend yield 2.40%   2.10%
Expected volatility 29.00%   34.00%
Risk-free interest rate 1.34%   0.96%
Expected life     5 years 3 months
Maximum [Member]      
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]      
Fair value per option grant $ 11.08   $ 20.62
Assumptions      
Dividend yield 2.50%   2.30%
Expected volatility 30.00%   36.00%
Risk-free interest rate 1.60%   2.00%
Expected life     6 years 6 months