Note 11 - Stock-Based Plans
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Jun. 30, 2012
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Stock-Based Plans Disclosure [Abstract] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Stock-Based Plans | Stock-Based Plans Stock Option Activity The following table summarizes stock option activity for the six-month period ended June 30, 2012:
The weighted average exercise price of stock options granted during the period was $36.34 per share and the related weighted average grant date fair value was $11.10 per share. Restricted Stock Unit Activity The following table summarizes restricted stock unit ("RSU") activity for the six-month period ended June 30, 2012:
The weighted average grant date fair value for RSUs awarded during the period was $36.60 per share. Stock-Based Compensation Expense The impact on our results of operations of recording stock-based compensation expense for the three and six months ended June 30, 2012 and 2011 was as follows:
Valuation Assumptions We calculated the fair value of each stock option award on the date of grant using the Black-Scholes option pricing model. The following weighted average assumptions were used for the three and six months ended June 30, 2012 and 2011:
Our computation of expected volatility is based on a combination of historical and market-based implied volatility from traded options on our common stock. Our computation of expected life is based on historical experience of similar awards, giving consideration to the contractual terms of the stock-based awards, vesting schedules and expectations of future employee behavior. The interest rate for periods within the contractual life of the award is based on the U.S. Treasury yield curve in effect at the time of grant. |