Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current Assets:
Cash and cash equivalents	$ 256,965	$ 187,661
Accounts receivable	3,530	4,713
Restricted investments	7,250
Other current assets	3,061	1,534
Total Current Assets	270,806	193,908
Restricted investments, noncurrent	647
Property and equipment, net of accumulated depreciation and amortization of $17,328 and $16,708	15,049	3,397
Patent costs, net of accumulated amortization of $1,622 and $2,626	5,042	4,913
Other assets	25	2,775
Total Assets	291,569	204,993
Current Liabilities:
Accounts payable	17,634	7,532
Accrued employee compensation	5,047	2,741
Current portion of long-term debt	92	89
Warrant liability	9,006	65,193
Deferred revenue	3,299	3,304
Other current liabilities	888	27
Total Current Liabilities	35,966	78,886
Long-term debt	1,576	1,668
Deferred rent and other long-term liabilities	6,835	760
Total Liabilities	44,377	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; 37,751,920 and 31,703,817 issued and outstanding at December 31, 2013 and 2012, respectively	4	3
Additional paid-in capital	790,424	554,927
Deficit accumulated during the development stage	(543,236)	(431,251)
Total Stockholders' Equity	247,192	123,679
Total Liabilities and Stockholders' Equity	$ 291,569	$ 204,993