Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current Assets:
Cash and cash equivalents	$ 73,551	$ 256,965
Short-term investments	136,793
Accounts receivable	2,416	3,530
Restricted investments		7,250
Other current assets	35,036	3,061
Total Current Assets	247,796	270,806
Restricted cash and investments	782	647
Property and equipment, net	38,501	15,049
Patent costs, net of accumulated amortization of $2,081 and $1,622 as of December 31, 2014 and 2013, respectively	5,891	5,042
Other assets	2,063	25
Total Assets	295,033	291,569
Current Liabilities:
Accounts payable	12,408	8,080
Accrued expenses	17,366	14,601
Current portion of long-term debt	98	92
Current portion of notes payable	2,492
Warrant liability		9,006
Deferred revenue	3,318	3,299
Other liabilities	1,185	888
Total Current Liabilities	36,867	35,966
Long-term debt	1,476	1,576
Notes payable	2,262
Deferred rent	6,775	6,835
Total Liabilities	47,380	44,377
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; 41,311,512 and 37,751,920 issued and outstanding as of December 31, 2014 and 2013, respectively	4	4
Additional paid-in capital	926,769	790,424
Accumulated other comprehensive loss	(95)
Accumulated deficit	(679,025)	(543,236)
Total Stockholders' Equity	247,653	247,192
Total Liabilities and Stockholders' Equity	$ 295,033	$ 291,569