Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 136,700	$ 87,282
Available-for-sale securities	31,528	76,734
Accounts receivable	457	74
Related party accounts receivable, net	1,030	578
Inventory	6,699
Prepaid expenses and other current assets	8,026	2,899
Total current assets	184,440	167,567
Restricted cash	7,647	7,647
Property and equipment, net	37,537	33,625
Other assets	283	138
Total assets	229,907	208,977
Current liabilities:
Accounts payable	14,217	6,436
Related party accounts payable, net	7,509
Accrued research and development costs	5,664	7,010
Accrued expenses	21,171	11,122
Current portion of capital lease obligations	261	233
Current portion of deferred rent	2,735	4,042
Current portion of deferred revenue	3,381	36,291
Total current liabilities	54,938	65,134
Capital lease obligations, net of current portion	308	422
Deferred rent, net of current portion	11,593	12,435
Deferred revenue, net of current portion	18,024	21,130
Other liabilities	992
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock, $0.001 par value, 75,000,000 shares authorized, no shares issued and outstanding at December 31, 2012 and December 31, 2011
Additional paid-in capital	648,955	542,141
Accumulated deficit	(505,016)	(432,392)
Accumulated other comprehensive income	5	6
Total stockholders' equity	144,052	109,856
Total liabilities and stockholders' equity	229,907	208,977
Class A common stock
Stockholders' equity:
Common stock	78	62
Class B common stock
Stockholders' equity:
Common stock	$ 30	$ 39