Condensed Consolidated Balance Sheets (Unaudited) (in thousands, except per share data) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 76,570	$ 27,357
Marketable securities, available-for-sale	87,919	44,146
Accounts receivable, net	10,956	9,097
Inventories	6,765	6,170
Prepaid expenses and other assets	8,704	8,425
Total current assets	190,914	95,195
Property and equipment, net	3,628	3,422
Prepaid expenses and other assets	2,645	2,676
Restricted cash	500	500
Total Assets	197,687	101,793
Current liabilities:
Accounts payable	8,658	3,135
Accrued expenses	12,272	14,369
Deferred revenue, current portion	13,026	7,398
Current portion of long-term debt, net	2,404	0
Total current liabilities	36,360	24,902
Deferred revenue, net of current portion	44,847	45,745
Long-term debt, net	47,389	49,772
Other long-term liabilities	2,343	1,364
Commitments and contingencies (Note 8)
Stockholders' equity (deficit):
Preferred stock - $0.001 par value; 20,000 shares authorized; no shares issued and outstanding	0	0
Common stock - $0.001 par value; 200,000 shares authorized; 124,483 and 114,533 shares issued and outstanding at March 31, 2014 and December 31, 2013, respectively	124	115
Additional paid-in capital	475,249	361,930
Accumulated other comprehensive (loss) income	(25)	17
Accumulated deficit	(408,600)	(382,052)
Total stockholders' equity (deficit)	66,748	(19,990)
Total Liabilities and Stockholders' Equity (Deficit)	$ 197,687	$ 101,793