CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash Flows From Operating Activities:
Net Loss	$ (81,550)	$ (59,123)	$ (44,799)
Adjustments to Reconcile Net Loss to Cash Used in Operating Activities:
Depreciation and Amortization	1,932	2,047	2,248
Amortization of Intangible Assets	1,013	1,090	1,913
Amortization and Premium of Marketable Securities	(1,366)	(660)	17
Realized (Gain) Loss on Sales and Maturities of Marketable Securities		(6)	5
Gain on Sale or Disposal of Assets	(21)	(74)	(58)
Stock-Based Compensation Expense	4,548	2,298	2,342
Non-Cash Interest Expense	97	226	307
Changes in Operating Assets and Liabilities:
Accounts and Other Receivables	(445)	126	154
Prepaid and Other Current Assets	(706)	33	241
Other Assets	276	(95)	34
Accounts Payable and Accrued Expenses	7,236	3,762	2,076
Other Liabilities	1,317	594	(138)
Net Cash Used in Operating Activities	(67,669)	(49,782)	(35,658)
Cash Flows From Investing Activities:
Sales and Maturities of Marketable Securities	38,894	52,360	51,003
Purchases of Marketable Securities	(112,118)	(69,255)	(52,717)
Acquisition of Property and Equipment	(4,219)	(303)	(509)
Proceeds from Sale or Disposal of Assets	21	218	68
Net Cash Used in Investing Activities	(77,422)	(16,980)	(2,155)
Cash Flows From Financing Activities:
Net Proceeds from Stock Issuances	295,697	83,784	36,023
Proceeds from Issuance of Stock from Employee Benefit Plans	5,403
(Payments) Issuance of Term Loan	(11,029)	(3,971)	5,000
Payment of Convertible Subordinated Debt			(12,503)
Payment of Other Liabilities	(472)	(55)	(86)
Net Cash Provided by Financing Activities	289,599	79,758	28,434
Effect of Exchange Rate Changes on Cash and Cash Equivalents	(3)	2	(9)
Net Increase (Decrease) in Cash and Cash Equivalents	144,505	12,998	(9,388)
Cash and Cash Equivalents at Beginning of Period	24,897	11,899	21,287
Cash and Cash Equivalents at End of Period	169,402	24,897	11,899
Supplemental Disclosure of Cash Flow Information
Cash Paid for Interest	$ 1,209	$ 1,384	$ 1,560