Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 273,644	$ 187,661
Accounts receivable	6,721	4,713
Restricted investments	7,250
Other current assets	2,807	1,534
Total current assets	290,422	193,908
Restricted investments, noncurrent	557
Property and equipment, net of accumulated depreciation and amortization of $17,345 and $16,708	8,244	3,397
Patent Costs, net of accumulated amortization of $1,538 and $2,626	5,231	4,913
Other assets	25	2,775
Total assets	304,479	204,993
Current liabilities:
Accounts payable	8,129	7,532
Accrued employee compensation	2,909	2,741
Current portion of long-term debt	91	89
Warrant liability	35,994	65,193
Deferred revenue	3,963	3,304
Other current liabilities	15	27
Total current liabilities	51,101	78,886
Long-term debt	1,599	1,668
Other long-term liabilities	4,795	760
Total liabilities	57,495	81,314
Commitments and contingencies
Stockholders' equity:
Preferred stock, $.0001 par value, 3,333,333 shares authorized; none issued and outstanding
Common stock, $.0001 par value, 50,000,000 shares authorized; Issued and outstanding: 37,533,695 at September 30, 2013 and 31,703,817 at December 31, 2012	4	3
Additional paid-in capital	781,396	554,927
Deficit accumulated during the development stage	(534,416)	(431,251)
Total stockholders' equity	246,984	123,679
Total liabilities and stockholders' equity	$ 304,479	$ 204,993