Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net loss	$ (155,349)	$ (91,373)
Adjustments to reconcile net income to cash flows in operating activities:
Depreciation and amortization	3,883	2,532
Amortization of premium on available-for-sale securities and non-cash interest	805	1,848
Loss on abandonment of patents	180	52
Stock-based compensation	25,769	14,578
Increase in warrant valuation		2,779
Changes in operating assets and liabilities, net:
Net (increase) decrease in accounts receivable	(317)	168
Net decrease (increase) in other assets	9,963	(29,168)
Net decrease in accounts payable, accrued expenses, deferred revenue and other liabilities	(3,127)	(4,506)
Net cash used in operations	(118,193)	(103,090)
Cash flows from investing activities:
Release and maturity of restricted investments		3,250
Purchase of restricted investments	(10,695)
Purchase of property and equipment	(2,316)	(22,305)
Patent costs	(982)	(1,062)
Purchase of available-for-sale securities	(49,632)	(272,189)
Maturity of available-for-sale securities	141,854	86,599
Net cash from (used in) investing activities	78,229	(205,707)
Cash flows from financing activities:
Proceeds from borrowings, net of debt issuance costs	19,601
Repayments of long-term debt and notes payable	(2,573)	(70)
Proceeds from exercise of options and warrants and the sale of common stock, net of offering costs	5,204	104,201
Net cash from financing activities	22,232	104,131
Decrease in cash and cash equivalents	(17,732)	(204,666)
Cash and cash equivalents:
Beginning of period	73,551	256,965
End of period	55,819	52,299
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	359	60
Supplemental schedule of non-cash investing activities and financing activities:
Accrued debt issuance costs related to the senior secured term loan	400
Property and equipment included in accrued expenses	211	1,165
Patent costs included in accrued expenses	105	187
Accrued legal and other fees for the October 9, 2015 common stock offering (See Note 11, Subsequent Event)	135
Capitalized interest	$ 99	36
Issuance of common stock in satisfaction of warrants		11,785
Tenant improvement paid by Landlord		154
Issuance of note payable in relation to the purchase of certain real and personal property located in Andover, Massachusetts		$ 4,613