Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 156,185	$ 187,661
Accounts receivable	3,788	4,713
Restricted investments	7,250
Other current assets	5,683	1,534
Total current assets	172,906	193,908
Restricted investments, noncurrent	557
Property and equipment, net of accumulated depreciation and amortization of $17,173 and $16,708	3,359	3,397
Patent Costs, net of accumulated amortization of $1,439 and $2,626	5,186	4,913
Other assets	1,625	2,775
Total assets	183,633	204,993
Current liabilities:
Accounts payable	6,727	7,532
Accrued employee compensation	1,986	2,741
Long-term debt, current portion	90	89
Warrant liability	79,116	65,193
Deferred revenue	4,499	3,304
Other current liabilities	15	27
Total current liabilities	92,433	78,886
Long-term debt, non-current portion	1,622	1,668
Other long-term liabilities	757	760
Total liabilities	94,812	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; 32,433,083 and 31,703,817 issued and outstanding	3	3
Additional paid-in capital	581,204	554,927
Deficit accumulated during the development stage	(492,386)	(431,251)
Total stockholders' equity	88,821	123,679
Total liabilities and stockholders' equity	$ 183,633	$ 204,993