CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash Flows from Operating Activities:
Net Loss	$ (36,348)	$ (27,289)
Adjustments to Reconcile Net Loss to Net Cash Used in Operating Activities:
Depreciation and Amortization	943	1,073
Amortization of Intangible Assets	507	583
Amortization and Premium of Marketable Securities	(1,949)	(157)
Realized Gain on Sales and Maturities of Marketable Securities		(6)
Gain on Sale or Disposal of Assets	(21)	(12)
Stock-Based Compensation Expense	1,384	1,088
Non-Cash Interest Expense	97	111
Changes in Operating Assets and Liabilities:
Accounts and Other Receivables	32	109
Prepaid and Other Current Assets	(424)	(493)
Other Assets	250	(99)
Accounts Payable and Accrued Expenses	109	(993)
Other Liabilities	162	573
Net Cash Used in Operating Activities	(35,258)	(25,512)
Cash Flows from Investing Activities:
Sales and Maturities of Marketable Securities	20,582	20,919
Purchases of Marketable Securities	(88,845)	(39,383)
Acquisition of Property and Equipment	(917)	(122)
Proceeds from Sale or Disposal of Assets	21	156
Net Cash Used in Investing Activities	(69,159)	(18,430)
Cash Flows from Financing Activities:
Net Proceeds from Stock Issuances	114,187	51,957
Proceeds from Issuance of Stock from Employee Benefit Plans	2,294
Payments of Term Loan	(11,029)	(1,323)
Payments of Other Liabilities	(29)	(29)
Net Cash Provided by Financing Activities	105,423	50,605
Effect of Exchange Rate Changes on Cash and Cash Equivalents	(3)	1
Net Increase in Cash and Cash Equivalents	1,003	6,664
Cash and Cash Equivalents at Beginning of Period	24,897	11,899
Cash and Cash Equivalents at End of Period	$ 25,900	$ 18,563