(10) Stock-Based Compensation
The following tables summarize information related to the company’s stock-based compensation:
| | | Restricted Stock Units | | Stock Options | | | | | | Weighted Average | | | | | | Weighted Average | | | | Number of | | Measurement | | Number of | | | | Exercise | | | | Units | | Date Fair Value | | Options | | | | Price | Outstanding at December 31, 2010 | | | 684,674 | | | $ | 16.38 | | | | 1,226,582 | | | | $ | 6.46 | | Granted (1) | | | 438,110 | | | | 17.41 | | | | — | | | | | — | | Exercised | | | — | | | | — | | | | (197,492 | ) | | | | 4.49 | | Vested | | | (326,271 | ) | | | 18.48 | | | | — | | | | | — | | Forfeited | | | (12,450 | ) | | | 16.67 | | | | — | | | | | — | | Expired | | | — | | | | — | | | | (5,648 | ) | | | | 4.14 | | Outstanding at September 30, 2011 | | | 784,063 | | | $ | 16.08 | | | | 1,023,442 | (2) | | | $ | 6.85 | |
(1) | The fair value of restricted stock unit grants is determined based on the closing market price of Orbital’s common stock on the date of grant. Such value is recognized as expense over the service period, net of estimated forfeitures. |
(2) | The weighted average remaining contractual term is 1.66 years. |
| | | Quarters Ended September 30, | (in millions) | | 2011 | | 2010 | Stock-based compensation expense | | $ | 1.8 | | | $ | 1.7 | | Income tax benefit related to stock-based compensation expense | | | 0.6 | | | | 0.7 | | Intrinsic value of options exercised computed as the market | | | | | | | | | price on the exercise date less the price paid to exercise the options | | | 0.7 | | | | 1.2 | | Cash received from exercise of options | | | 0.3 | | | | 2.2 | | Tax benefit recorded as credits to additional paid-in capital related | | | | | | | | | to stock-based compensation transactions | | | 0.3 | | | | 0.4 | | | | | | | | | | | | | | | Nine Months Ended September 30, | (in millions) | | 2011 | | 2010 | Stock-based compensation expense | | $ | 4.7 | | | $ | 3.5 | | Income tax benefit related to stock-based compensation expense | | | 1.5 | | | | 1.4 | | Intrinsic value of options exercised computed as the market | | | | | | | | | price on the exercise date less the price paid to exercise the options | | | 2.5 | | | | 5.4 | | Cash received from exercise of options | | | 0.9 | | | | 9.7 | | Tax benefit recorded as credits to additional paid-in capital related | | | | | | | | | to stock-based compensation transactions | | | 1.0 | | | | 2.0 | |
| | | As of | | (in millions) | | September 30, 2011 | | Shares of common stock available for grant under stock-based incentive plans | | | 0.8 | | Aggregate intrinsic value of restricted stock units that are expected to vest | | $ | 10.0 | | Unrecognized compensation expense related to non-vested restricted stock units, expected to | | | | | be recognized over a weighted-average period of 2.38 years | | | 11.4 | | Aggregate intrinsic value of stock options outstanding, all fully vested | | | 6.1 | |
|