Cash, Cash Equivalents and Short-term Investments (Tables)

9 Months Ended

Sep. 30, 2012

Cash, Cash Equivalents and Short-term Investments [Abstract]

Summary of cash and cash equivalents and short-term investments

Cash and cash equivalents and short-term investments consisted of the following as of September 30, 2012 and December 31, 2011 (in thousands):

September 30, 2012

	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Cash	$	59,845	$	—	$	—	$	59,845
Cash equivalents:
Money market mutual funds		50,432		—		—		50,432
Total cash and cash equivalents	$	110,277		—		—	$	110,277

December 31, 2011

	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
Cash	$	59,033	$	—	$	—		$	59,033
Cash equivalents:
Money market mutual funds		4,201		—		—			4,201
Commercial paper		2,749		—		—			2,749
Total cash equivalents		6,950		—		—			6,950
Total cash and cash equivalents		65,983		—		—			65,983
Short-term investments:
Certificate of deposit		750		—		(4	)		746
Municipal securities		33,568		30		(6	)		33,592
Commercial paper		3,645		1		(1	)		3,645
Corporate bonds		4,910		3		(14	)		4,899
Total short-term investments		42,873		34		(25	)		42,882
Cash, cash equivalents and short-term investments	$	108,856	$	34	$	(25	)	$	108,865