Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 72,021	$ 41,228
Trade accounts receivable, net	6,665	5,643
Inventory	9,936	12,886
Prepaid expenses and other current assets	4,257	1,968
Total current assets	92,879	61,725
Property and equipment, net	13,011	13,561
Other assets	6,614	5,400
Total assets	112,504	80,686
Current liabilities:
Accounts payable	4,622	4,592
Accrued expenses	18,865	14,343
Common stock warrant liabilities	31,341	9,493
Accrued compensation	3,952	4,226
Total current liabilities	58,780	32,654
Long-term debt	28,802	28,481
Other long-term liabilities	6,496	5,078
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.001 par value; 200,000 shares authorized at December 31, 2013 and 2012; 138,927 and 100,809 shares issued and outstanding at December 31, 2013 and 2012, respectively.	139	101
Additional paid-in capital	428,534	343,763
Accumulated deficit	(410,247)	(329,391)
Total stockholders’ equity	18,426	14,473
Total liabilities and stockholders’ equity	$ 112,504	$ 80,686