Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net loss	$ (62,147)	$ (61,135)
Adjustments to reconcile net loss to net cash flows used in operating activities:
Depreciation and amortization	1,483	711
Amortization of premium on available-for-sale securities	1,127	0
Loss on abandonment of patents	52	334
Stock-based compensation	9,929	3,989
Loss on change in warrant valuation	7,035	28,851
Changes in operating assets and liabilities, net:
Net (increase) decrease in accounts receivable and other assets	(20,957)	549
Net decrease in accounts payable, accrued expenses and other liabilities	(4,291)	(294)
Net cash used in operating activities	(67,769)	(26,995)
Cash flows from investing activities:
Release and maturity of restricted investments	3,250	0
Purchase of restricted investments	0	(7,807)
Purchase of property and equipment	(9,841)	(435)
Patent costs	(628)	(931)
Purchase of available-for-sale securities	(226,616)	0
Maturity of available-for-sale securities	48,669	0
Net cash used in investing activities	(185,166)	(9,173)
Cash flows from financing activities:
Proceeds from exercise of options and warrants and the sale of common stock, net of offering costs	98,771	4,915
Repayments of long-term debt	(47)	(45)
Other financing activities, net	0	(178)
Net cash provided by financing activities	98,724	4,692
Decrease in cash and cash equivalents	(154,211)	(31,476)
Cash and cash equivalents:
Beginning of period	256,965	187,661
End of period	102,754	156,185
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	40	102
Supplemental schedule of non-cash investing activities and financing activities:
Issuance of common stock in satisfaction of warrants and other liabilities	6,215	14,928
Tenant improvements paid by landlord	65	0
Property and equipment included in accrued expenses	422	0
Receivable for warrants exercised	$ 0	$ 2,624