Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 63,692	$ 74,297
Available-for-sale securities	152,173	174,037
Accounts receivable	862	10
Related party accounts receivable, net	32,987	25,829
Inventory	4,950	4,954
Prepaid expenses and other current assets	9,212	10,603
Total current assets	263,876	289,730
Restricted cash	8,147	8,147
Property and equipment, net	27,477	29,826
Other assets	6,028	5,810
Total assets	305,528	333,513
Current liabilities:
Accounts payable and related party accounts payable, net	5,227	9,762
Accrued research and development costs	9,270	3,574
Accrued expenses	18,735	22,612
Current portion of capital lease obligations	1,177	1,152
Current portion of deferred rent	5,006	4,992
Current portion of deferred revenue	7,191	7,191
Current portion of notes payable	13,207	11,258
Total current liabilities	59,813	60,541
Capital lease obligations, net of current portion	2,268	2,571
Deferred rent, net of current portion	9,935	10,522
Deferred revenue, net of current portion	7,191	8,989
Notes payable, net of current portion	158,159	162,338
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.001 par value, 75,000,000 shares authorized, no shares issued and outstanding
Additional paid-in capital	1,068,685	1,055,876
Accumulated deficit	(1,000,668)	(967,446)
Accumulated other comprehensive income (loss)	3	(19)
Total stockholders' equity	68,162	88,552
Total liabilities and stockholders' equity	305,528	333,513
Class A common stock
Stockholders' equity:
Common stock	126	125
Class B common stock
Stockholders' equity:
Common stock	$ 16	$ 16