Number of Units | Weighted Average Grant-Date Fair Value | |||||
Outstanding as of January 1, 2011 | 14.0 | $ | 96 | |||
Units granted | 5.4 | 193 | ||||
Units vested | (5.1 | ) | 73 | |||
Units forfeited | (1.2 | ) | 122 | |||
Outstanding as of December 31, 2011 | 13.1 | 143 | ||||
Units granted | 8.2 | 209 | ||||
Units vested | (4.2 | ) | 110 | |||
Units forfeited | (1.7 | ) | 168 | |||
Outstanding as of December 31, 2012 | 15.4 | 184 | ||||
Units granted | 7.2 | 283 | ||||
Units vested | (4.5 | ) | 160 | |||
Units forfeited | (1.8 | ) | 209 | |||
Outstanding as of December 31, 2013 | 16.3 | $ | 233 |