Description of Business and Basis of Presentation (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Schedule of computation of basic and diluted net income (loss) per share
Net income (loss)	$ 2,658	$ (1,217)	$ 3,162	$ (1,021)
Effect of assumed conversion of convertible debentures
Weighted-average common shares outstanding	28,672	27,669	28,397	27,478
Weighted-average common shares outstanding, assuming dilution	28,780	27,669	28,680	27,478
Basic	$ 0.09	$ (0.04)	$ 0.11	$ (0.04)
Diluted	$ 0.09	$ (0.04)	$ 0.11	$ (0.04)
Outstanding options to purchase common stock [Member]
Effect of assumed conversion of convertible debentures
Effect of potentially dilutive securities	85		223
Restricted Stock Awards [Member]
Effect of assumed conversion of convertible debentures
Effect of potentially dilutive securities	5		23
Restricted Stock Unit Awards [Member]
Effect of assumed conversion of convertible debentures
Effect of potentially dilutive securities			4
Employee stock purchase plan [Member]
Effect of assumed conversion of convertible debentures
Effect of potentially dilutive securities	18		33