Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating activities
Net loss	$ (8,412,000)	$ (38,845,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Impairment of property and equipment	232,000	7,600,000
Depreciation and amortization	9,561,000	2,764,000
Accretion	224,000
Loss (gain) on disposal of fixed assets	230,000	(122,000)
Stock-based compensation	1,180,000	2,578,000
Non-cash interest expense	344,000	139,000
Amortization of premium and discount on investments	33,000	218,000
Changes in operating assets and liabilities:
Restricted cash	135,000	598,000
Accounts receivable	7,000	(674,000)
Tenant improvement allowance receivable		5,637,000
Prepaid expenses and other current assets	120,000	(270,000)
Other noncurrent assets	75,000	244,000
Accounts payable	(2,958,000)	(2,585,000)
Accrued expenses	(3,848,000)	(4,263,000)
Deferred revenue	573,000	(18,007,000)
Lease exit obligation	(5,205,000)	7,798,000
Deferred rent	(10,569,000)	(6,033,000)
Other liabilities	37,000
Net cash used in operating activities	(18,241,000)	(43,223,000)
Investing activities
Purchases of marketable securities	(11,581,000)	(38,056,000)
Proceeds from maturities and sales of marketable securities	9,050,000	102,107,000
Purchases of property and equipment	(14,000)	(12,875,000)
Proceeds from sale of property and equipment	1,241,000	183,000
Net cash (used in) provided by investing activities	(1,304,000)	51,359,000
Financing activities
Proceeds from issuance of common stock, net of issuance costs	10,217,000
Proceeds from exercise of stock options and issuance of common and restricted stock	278,000	191,000
Loan proceeds		10,000,000
Loan issuance cost		(1,388,000)
Principal payments on loans payable	(8,517,000)	(7,785,000)
Net cash provided by financing activities	1,978,000	1,018,000
Net decrease in cash and cash equivalents	(17,567,000)	9,154,000
Cash and cash equivalents at beginning of period	52,306,000	50,826,000
Cash and cash equivalents at end of period	34,739,000	59,980,000
Supplemental cash flow information
Cash paid for interest	$ 1,619,000	1,447,000
Non-cash financing activity
Fair value of warrants issued in connection with loan payable		$ 413,000