Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2011

Fair Value of Financial Instruments

Financial assets and liabilities subject to fair value measurements (excluding restricted cash and cash equivalents (Alios))

			Fair Value Measurements as of June 30, 2011
					Fair Value Hierarchy
			Total		Level 1		Level 2		Level 3
			(in thousands)
Financial assets carried at fair value:
	Cash equivalents:
		Money market funds	$	373,003	$	373,003	$	—	$	—
		Government-sponsored enterprise securities		35,906		35,906		—		—
	Marketable securities:
		U.S. Treasury securities		9,547		9,547		—		—
		Government-sponsored enterprise securities		125,749		125,749		—		—
	Restricted cash			34,114		34,114		—		—
		Total	$	578,319	$	578,319	$	—	$	—
Financial liabilities carried at fair value:
	Embedded derivative related to 2012 Notes		$	4,973	$	—	$	—	$	4,973
	Liability related to sale of potential future milestone payments			87,131		—		—		87,131
		Total	$	92,104	$	—	$	—	$	92,104

Reconciliation of financial liabilities measured at fair value using significant unobservable inputs

		Six Months Ended June 30, 2011
		(in thousands)
Balance, December 31, 2010		$	89,888
	Change in fair value of derivative instruments		7,818
	Redemption of a portion of the 2012 Notes		(5,602	)
Balance, June 30, 2011		$	92,104