Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Numerator, in thousands
Net income used for calculation of basic EPS	$ 4,222	$ 27,858	$ 7,145	$ 15,516
Interest expense on convertible debt	292	1,289	1,004	3,774
Change in fair value of derivative liabilities	(174)	(760)	(462)	(2,115)
Loss on extinguishment of outstanding debt, as if converted	32	(8,496)	(94)	(10,497)
Total adjustments	150	(7,967)	448	(8,838)
Net income used for calculation of diluted EPS	$ 4,372	$ 19,891	$ 7,593	$ 6,678
Denominator
Weighted average shares outstanding, basic	48,515,071	42,900,269	47,011,243	42,035,025
Effect of dilutive potential common shares
Shares underlying Convertible Senior Secured Notes	1,961,410	6,751,484	3,703,320	7,308,192
Shares issuable to settle interest make-whole derivatives	98,879	825,057		687,148
Warrants to purchase common stock		20,857		20,905
Stock options, stock appreciation rights, and non-vested stock options and ESPP awards	1,015,437	327,966	344,903	326,916
Total potential dilutive common shares	3,075,726	7,925,364	4,048,223	8,343,161
Weighted average shares outstanding, diluted	51,590,797	50,825,633	51,059,466	50,378,186
Net income per share, basic	$ 0.09	$ 0.65	$ 0.15	$ 0.37
Net income per share, diluted	$ 0.08	$ 0.39	$ 0.15	$ 0.13
Warrant to purchase common stock
Loss Per Share
Common stock equivalents excluded in the calculation of diluted loss per share	40,850		38,424
Stock options, stock appreciation rights, non-vested stock options and ESSP awards
Loss Per Share
Common stock equivalents excluded in the calculation of diluted loss per share	39,289		13,240