Cash and Investments

3 Months Ended

Mar. 31, 2013

Investments and Cash [Abstract]

Cash and Investments

Cash and Investments

The following table presents cash, cash equivalents and available-for-sale investments for the periods presented (in thousands):

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Market Value
March 31, 2013:
Cash	$	107,321	$	—	$	—		$	107,321
Cash equivalents:
Money market funds	126,125		—		—			126,125
Commercial paper	31,488		5		—			31,493
Short-term investments:
Commercial paper	67,218		31		(12		)	67,237
Certificates of deposit	2,000		7		—			2,007
U.S. treasury securities	31,695		17		—			31,712
U.S. agency securities	336,038		392		(43		)	336,387
Corporate debt securities	126,392		59		(40		)	126,411
Municipal securities	1,610		4		—			1,614
Total cash, cash equivalents, and short-term investments	$	829,887	$	515	$	(95	)	$	830,307
December 31, 2012:
Cash	$	103,536	$	—	$	—		$	103,536
Cash equivalents:
Money market funds	148,384		—		—			148,384
Commercial paper	18,487		1		—			18,488
Short-term investments:
Commercial paper	46,352		9		—			46,361
Certificates of deposit	2,000		5		—			2,005
U.S. treasury securities	18,184		13		—			18,197
U.S. agency securities	302,991		460		(1		)	303,450
Corporate debt securities	107,585		10		(78		)	107,517
Municipal securities	1,612		—		(1		)	1,611
Total cash, cash equivalents, and short-term investments	$	749,131	$	498	$	(80	)	$	749,549

The following table presents available-for-sale investments by contractual maturity date (in thousands) as of March 31, 2013:

	Amortized Cost		Estimated Fair Market Value
Due in one year or less	$	297,038	$	297,388
Due after one year through two years	267,915		267,980
Total	$	564,953	$	565,368