CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash Flows from Operating Activities:
Net Loss	$ (59,488)	$ (42,316)
Adjustments to Reconcile Net Loss to Net Cash Used in Operating Activities:
Depreciation and Amortization	1,422	1,576
Amortization of Intangible Assets	760	836
Amortization and Premium of Marketable Securities	(1,232)	(420)
Realized Gain on Sales and Maturities of Marketable Securities		(6)
Gain on Sale or Disposal of Assets	(21)	(74)
Stock-Based Compensation Expense	3,400	1,614
Non-Cash Interest Expense	97	169
Changes in Operating Assets and Liabilities:
Accounts and Other Receivables	(846)	138
Prepaid and Other Current Assets	(1,457)	(8)
Other Assets	267	(80)
Accounts Payable and Accrued Expenses	2,954	1,495
Other Liabilities	1,432	620
Net Cash Used in Operating Activities	(52,712)	(36,456)
Cash Flows from Investing Activities:
Sales and Maturities of Marketable Securities	30,679	45,432
Purchases of Marketable Securities	(92,400)	(57,900)
Acquisition of Property and Equipment	(1,901)	(193)
Proceeds from Sale or Disposal of Assets	21	218
Net Cash Used in Investing Activities	(63,601)	(12,443)
Cash Flows from Financing Activities:
Net Proceeds from Stock Issuances	114,187	62,872
Proceeds from Issuance of Stock from Employee Benefit Plans	2,931
Payments of Term Loan	(11,029)	(2,646)
Payments of Other Liabilities	(44)	(41)
Net Cash Provided by Financing Activities	106,045	60,185
Effect of Exchange Rate Changes on Cash and Cash Equivalents	(3)	2
Net (Decrease) Increase in Cash and Cash Equivalents	(10,271)	11,288
Cash and Cash Equivalents at Beginning of Period	24,897	11,899
Cash and Cash Equivalents at End of Period	$ 14,626	$ 23,187