Description of Business and Basis of Presentation (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Schedule of computation of basic and diluted net income (loss) per share
Net income	$ 6,027	$ 5,228	$ 9,154	$ 4,307
Effect of assumed conversion of convertible debentures
Weighted-average common shares outstanding	28,884	28,736	28,857	28,511
Weighted-average common shares outstanding, assuming dilution	28,940	28,748	28,883	28,695
Net income per share
Basic	$ 0.21	$ 0.18	$ 0.32	$ 0.15
Diluted	$ 0.21	$ 0.18	$ 0.32	$ 0.15
Stock Options
Effect of assumed conversion of convertible debentures
Effect of potentially dilutive securities	35	8	17	153
Restricted Stock [Member]
Effect of assumed conversion of convertible debentures
Effect of potentially dilutive securities	1	3	4	11
Restricted Stock Unit
Effect of assumed conversion of convertible debentures
Effect of potentially dilutive securities	20	0	5	3
Employee Stock Purchase Plan
Effect of assumed conversion of convertible debentures
Effect of potentially dilutive securities	0	1	0	17