XML 97 R81.htm IDEA: XBRL DOCUMENT v3.3.1.900
Incentive Plans (Assumptions used in Valuation Performance Awards Granted) (Details) - Performance Based Restricted Stock [Member]
12 Months Ended
Dec. 31, 2015
item
$ / shares
Dec. 31, 2014
item
$ / shares
Dec. 31, 2013
item
$ / shares
Assumptions      
Expected volatility 26.00% 29.00%  
Risk-free interest rate 0.85% 0.65%  
Stock beta 0.813 0.843  
Expected life 3 years 3 years 3 years
Minimum [Member]      
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]      
Granted restricted stock, fair value | $ / shares $ 44.03 $ 33.90 $ 39.50
Assumptions      
Expected volatility     31.00%
Risk-free interest rate     0.41%
Stock beta     0.907
Maximum [Member]      
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]      
Granted restricted stock, fair value | $ / shares $ 48.12 $ 51.30 $ 68.01
Assumptions      
Expected volatility     32.00%
Risk-free interest rate     0.62%
Stock beta     0.908