Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation (Schedule of Weighted Average Assumptions) (Details)

v2.4.0.6
Stock-Based Compensation (Schedule of Weighted Average Assumptions) (Details) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock options granted 358,169 340,973 385,924
Stock Options [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected term, years 4 years 9 months 11 days 5 years 1 month 13 days [1] 4 years 6 months 11 days
Expected stock price volatility 32.20% 30.76% [1] 28.79%
Risk-free interest rate 0.88% 1.84% [1] 1.91%
Expected dividend yield 1.80% 1.31% [1] 1.64%
Weighted average grant date fair value 11.57 16.09 [1] 10.08
Simplified Method [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock options granted   53,720  
Vesting period   5 years  
[1] During the year ended December 31, 2011, the Company granted two stock option awards totaling 53,720 shares that vest 100% on the fifth anniversary of the grant date. Because the Company did not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term for these grants, the Company utilized the simplified method in developing an estimate of the expected term of these options.