CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash Flows from Operating Activities:
Net Loss	$ (17,332)	$ (13,516)
Adjustments to Reconcile Net Loss to Net Cash Used in Operating Activities:
Depreciation and Amortization	468	544
Amortization of Intangible Assets	253	291
Amortization and Premium of Marketable Securities	(1,324)	(373)
Realized Gain on Sales and Maturities of Marketable Securities		(4)
Loss on Sales or Disposal of Assets		23
Stock-Based Compensation Expense	708	641
Non-Cash Interest Expense	56	57
Changes in Operating Assets and Liabilities:
Accounts and Other Receivables	(60)	30
Prepaid and Other Current Assets	(879)	(672)
Other Assets	188	(131)
Accounts Payable and Accrued Expenses	206	(1,049)
Other Liabilities	516	606
Net Cash Used in Operating Activities	(17,200)	(13,553)
Cash Flows from Investing Activities:
Sales and Maturities of Marketable Securities	7,394	5,912
Purchases of Marketable Securities	(53,809)	(33,388)
Acquisition of Property and Equipment	(162)	(42)
Proceeds from Sales or Disposal of Assets		11
Net Cash Used in Investing Activities	(46,577)	(27,507)
Cash Flows from Financing Activities:
Net Proceeds from Stock Issuances	114,187	51,929
Proceeds from Issuance of Stock from Employee Benefit Plans	1,660
Payments of Term Loan	(1,323)
Payments of Other Liabilities	(15)	(15)
Net Cash Provided by Financing Activities	114,509	51,914
Effect of Exchange Rate Changes on Cash and Cash Equivalents	(2)	2
Net Increase in Cash and Cash Equivalents	50,730	10,856
Cash and Cash Equivalents at Beginning of Period	24,897	11,899
Cash and Cash Equivalents at End of Period	$ 75,627	$ 22,755