| The following table summarizes performance share activity for the years ended December 31: | ||||||||||||||||||
| 2013 | 2012 | 2011 | ||||||||||||||||
| Weighted Average | Weighted Average | Weighted Average | ||||||||||||||||
| Number of | Grant Date | Number of | Grant Date | Number of | Grant Date | |||||||||||||
| Awards | Fair Value | Awards | Fair Value | Awards | Fair Value | |||||||||||||
| Undistributed balance — | ||||||||||||||||||
| As of January 1 | 1,089,084 | $ | 79.27 | 878,872 | $ | 78.55 | 760,645 | $ | 73.99 | |||||||||
| Granted | 353,734 | 96.87 | 467,531 | 81.55 | 415,024 | 84.58 | ||||||||||||
| Distributed | (507,083) | 75.16 | ― | ― | (206,410) | 72.77 | ||||||||||||
| Performance change | (6,949) | 77.01 | (178,838) | 81.27 | (39,323) | 82.10 | ||||||||||||
| Forfeited | (33,151) | 91.34 | (78,481) | 80.21 | (51,064) | 80.20 | ||||||||||||
| As of December 31 | 895,635 | $ | 88.12 | 1,089,084 | $ | 79.27 | 878,872 | $ | 78.55 | |||||||||