Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net loss	$ (61,559)	$ (28,273)
Adjustments to reconcile net loss to net cash flows used in operating activities:
Depreciation and amortization	1,280	523
Amortization of premium on available-for-sale securities and other non-cash interest expense	315	519
Loss on abandonment of patents and disposal of property and equipment	131	6
Stock-based compensation	14,156	4,342
Increase in warrant valuation		3,251
Changes in operating assets and liabilities, net:
Net increase in accounts receivable		(4,319)
Net decrease (increase) in other assets	7,413	(6,018)
Net (decrease) increase in accounts payable, accrued expenses, deferred revenue and other liabilities	(5,084)	1,704
Net cash used in operating activities	(43,348)	(28,265)
Cash flows from investing activities:
Purchase of property and equipment	(532)	(5,326)
Patent costs	(391)	(294)
Purchase of available-for-sale securities		(176,669)
Sale of available-for-sale securities	44,750
Net cash provided by (used in) investing activities	43,827	(182,289)
Cash flows from financing activities:
Proceeds from exercise of options and warrants	431	2,713
Repayments of long-term debt	(25)	(23)
Net cash provided by financing activities	406	2,690
Increase (decrease) in cash and cash equivalents	885	(207,864)
Cash and cash equivalents:
Beginning of period	73,551	256,965
End of period	74,436	49,101
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest	18	20
Supplemental Schedule of Noncash Investing Activities and Financing Activities:
Issuance of common stock in satisfaction of warrants and other liabilities		3,044
Capitalized interest	99
Tenant improvements paid by landlord		593
Property and equipment included in accrued expenses	45	3,533
Patent costs included in accrued expenses	$ 100	$ 200