Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2012

Fair Value of Financial Instruments

Financial assets subject to fair value measurements (excluding Alios' cash equivalents (Alios))

	Fair Value Measurements as of September 30, 2012
			Fair Value Hierarchy
	Total		Level 1		Level 2		Level 3
	(in thousands)
Financial assets carried at fair value:
Cash equivalents:
Money market funds	$	220,697	$	220,697	$	—	$	—
Government-sponsored enterprise securities		17,568		17,568		—		—
Marketable securities:
U.S. Treasury securities		222,483		222,483		—		—
Government-sponsored enterprise securities		342,718		342,718		—		—
Commercial paper		251,660		—		251,660		—
Corporate debt securities		44,795		—		44,795		—
Restricted cash		32,166		32,166		—		—
Total	$	1,132,087	$	835,632	$	296,455	$	—