Cash equivalents, and investments, all of which are classified as available-for-sale securities, consisted of the following (in thousands):

	March 31, 2014									December 31, 2013
								Estimated									Estimated
			Unrealized		Unrealized			Fair				Unrealized		Unrealized			Fair
	Cost		Gain		(Loss)			Value		Cost		Gain		(Loss)			Value
Money market funds	$	25,344	$	—	$	—		$	25,344	$	57,296	$	—	$	—		$	57,296
Corporate notes and commercial paper		176,466		54		(42	)		176,478		182,426		62		(16	)		182,472
U.S. government agency securities		78,016		29		(14	)		78,031		75,278		23		(12	)		75,289
	$	279,826	$	83	$	(56	)	$	279,853	$	315,000	$	85	$	(28	)	$	315,057
Classified as:
Cash equivalents								$	37,151								$	113,794
Short-term investments									198,433									150,892
Long-term investments									44,269									50,371
Total cash equivalents and investments								$	279,853								$	315,057