Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 28,833	$ 35,688
Available-for-sale securities	62,938	88,340
Restricted cash	101	101
Accounts receivable	4,248	3,313
Prepaid expenses and other current assets	3,178	4,654
Total current assets	99,298	132,096
Restricted cash	584	584
Property and equipment, net	15,749	14,502
Other assets	139	144
Intangible assets, net	1,445	1,525
In-process research and development	6,200	6,200
Goodwill	3,605	3,605
Total assets	127,020	158,656
Current liabilities:
Accounts payable, accrued expenses and other	42,979	37,236
Deferred revenues	59,506	59,275
Deferred rent	1,224	1,285
Long-term debt, current portion		13,346
Total current liabilities	103,709	111,142
Deferred revenues, net of current portion	23,229	35,682
Deferred rent, net of current portion	5,156	5,401
Deferred tax incentives, net of current portion	468	496
Long-term debt, net of current portion	122,080	106,806
Accrued interest	1,200	1,200
Total liabilities	255,842	260,727
Commitments and contingencies (Note 10)
Non-controlling interest	396	69
Stockholders' deficit:
Preferred stock, $0.01 par value: 10,000 shares authorized at March 31, 2015 and December 31, 2014; no shares issued or outstanding at March 31, 2015 or December 31, 2014
Common stock, $0.01 par value: 200,000 shares authorized at March 31, 2015 and December 31, 2014; 109,386 and 106,697 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	1,094	1,067
Additional paid-in capital	559,175	552,037
Accumulated other comprehensive loss	(27)	(74)
Accumulated deficit	(689,460)	(655,170)
Total stockholders' deficit	(129,218)	(102,140)
Total liabilities, non-controlling interest and stockholders' deficit	$ 127,020	$ 158,656