Employee Stock Purchase Plan

12 Months Ended

Dec. 31, 2011

Employee Stock Purchase Plan [Abstract]

Employee Stock Purchase Plan

(13) Employee Stock Purchase Plan

On May 12, 2011, the Company adopted, based on approval by the Board of Directors and stockholders, an employee stock purchase plan (the “2011 ESPP”). The 2011 ESPP was designed to replace the Company’s previous employee stock purchase plan which was adopted on February 15, 2001 (the “2001 ESPP”) and expired pursuant to its ten-year term. The terms and conditions of the 2011 ESPP are unchanged from the terms and conditions of the 2001 ESPP. All of the Company’s employees who have at least 90 days of service, customarily work at least 20 hours per week and customarily work more than five months per year are eligible to participate, except for employees who own shares possessing five percent or more of the total combined voting power or value of the Company or its subsidiaries. Eligible employees may join the plan every six months. Purchases of common stock are priced at the lower of the stock price less 15% on the first day or the last day of the six-month period. The Company has reserved for issuance 1,200,000 shares of common stock under the 2011 ESPP. During the year ended December 31, 2011, no shares were issued under the 2001 ESPP and 73,717 shares were issued under the 2011 ESPP. During the years ended December 31, 2010 and 2009, the Company had issued 88,343 and 97,332 shares, respectively, under the 2001 ESPP. As of December 31, 2011 a total of 1,126,283 shares were available for issuance under the 2011 ESPP.

The fair value of the employees’ purchase rights granted in each of the six month offering periods during 2011, 2010 and 2009 was estimated on the date of grant using the Black-Scholes-Merton option-pricing model with the following weighted average assumptions:

	Six Month Offering Periods Ending
	December  31, 2011			June  30, 2011			December  31, 2010			June  30, 2010			December  31, 2009			June  30, 2009
Expected volatility		45.86	%		46.58	%		47.44	%		48.10	%		48.83	%		47.32	%
Expected term		6 months			6 months			6 months			6 months			6 months			6 months
Risk-free interest rate		0.10	%		0.19	%		0.22	%		0.20	%		0.35	%		0.27	%
Divided yield		None			None			None			None			None			None

The per share fair value of those purchase rights granted in each of the six month offering periods during 2011, 2010 and 2009 were as follows:

	Six Month Offering Periods Ending
	December  31, 2011		June  30, 2011		December  31, 2010		June  30, 2010		December  31, 2009		June  30, 2009
Grant-date fair value	$	19.65	$	12.34	$	9.20	$	7.69	$	7.71	$	8.36