Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended			401 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (111,985)	$ (121,287)	$ (2,318)	$ (543,236)
Adjustments to reconcile net loss to net cash flows used in operating activities:
Depreciation and amortization	1,277	1,525	1,300	23,247
Loss on abandonment of patents and disposal of property and equipment	590	357	190	3,226
Realized gain on sale of short-term securities-available-for-sale				(3,863)
Write-down of short-term securities-available-for-sale				17,001
Impairment charge on real estate owned			109	1,445
Stock-based compensation	11,127	3,078	3,129	43,200
Acquired in-process research and development				29,461
Increase (decrease) on warrant valuation	22,027	91,938	(33,022)	88,995
Net increase (decrease) in accounts receivable, other current assets and other assets	2,801	(3,587)	(1,063)	(5,960)
Net increase (decrease) in accounts payable, accrued employee compensation, and other liabilities	9,468	(1,718)	7,996	21,881
Net cash used in operating activities	(64,695)	(29,694)	(23,679)	(324,603)
Cash flows from investing activities:
Purchase of restricted investments	(7,897)			(7,897)
Purchase of property and equipment	(2,370)	(108)	(1,178)	(22,357)
Patent costs	(1,405)	(1,037)	(1,127)	(11,934)
Purchase of marketable securities				(112,993)
Sale of marketable securities				117,724
Acquisition costs				(2,389)
Net cash used in investing activities	(11,672)	(1,145)	(2,305)	(39,846)
Cash flows from financing activities:
Proceeds from exercise of options and warrants, and the sale of common stock, warrants, and partnership units, net of offering costs	145,986	178,681	32,380	622,545
Repayments of long-term debt	(89)	(85)	(81)	(519)
Other financing activities, net	(226)			(612)
Net cash provided by financing activities	145,671	178,596	32,299	621,414
Increase in cash and cash equivalents	69,304	147,757	6,315	256,965
Cash and cash equivalents:
Beginning of period	187,661	39,904	33,589
End of period	256,965	187,661	39,904	256,965
Supplemental disclosure of cash flow information:
Cash paid during the year for interest	144	86	90	719
Supplemental schedule of noncash investing activities and financing activities:
Short-term securities-available-for-sale received in connection with the private offering				17,897
Issuance of common stock in satisfaction of warrants and other liabilities	78,214	32,191	643	111,048
Tenant improvements paid by landlord	6,214			6,214
Property and equipment included in accounts payable and other liabilities	3,964			3,964
Building
Supplemental schedule of noncash investing activities and financing activities:
Issuance of common stock				750
Assumption of long-term debt				2,200
Other Assets
Supplemental schedule of noncash investing activities and financing activities:
Issuance of common stock				8,075
Assumption of long-term debt				$ 2,124