Marketable Securities (Tables)

3 Months Ended

Jun. 30, 2013

Cash and Cash Equivalents [Abstract]

Summary of cash, cash equivalents and marketable securities

A summary of the Company’s cash, cash equivalents and marketable securities is shown below:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(in thousands)
As of June 30, 2013
Cash and cash equivalents:
Cash and money market funds	$	530,567	$	—	$	—		$	530,567
U.S. Treasury securities	680		—		—			680
Total cash and cash equivalents	$	531,247	$	—	$	—		$	531,247
Marketable securities:
U.S. Treasury securities (due within 1 year)	$	3,050	$	—	$	—		$	3,050
Government-sponsored enterprise securities (due within 1 year)	598,440		17		(46		)	598,411
Commercial paper (due within 1 year)	192,702		176		—			192,878
Corporate debt securities (due within 1 year)	105,220		—		(110		)	105,110
Total marketable securities	$	899,412	$	193	$	(156	)	$	899,449
Total cash, cash equivalents and marketable securities	$	1,430,659	$	193	$	(156	)	$	1,430,696
As of December 31, 2012
Cash and cash equivalents:
Cash and money market funds	$	489,407	$	—	$	—		$	489,407
Total cash and cash equivalents	$	489,407	$	—	$	—		$	489,407
Marketable securities:
U.S. Treasury securities (due within 1 year)	$	111,350	$	2	$	(2	)	$	111,350
Government-sponsored enterprise securities (due within 1 year)	440,181		49		(5		)	440,225
Commercial paper (due within 1 year)	225,294		155		—			225,449
Corporate debt securities (due within 1 year)	15,429		1		(1		)	15,429
Corporate debt securities (due after 1 year through 5 years)	39,358		10		(13		)	39,355
Total marketable securities	$	831,612	$	217	$	(21	)	$	831,808
Total cash, cash equivalents and marketable securities	$	1,321,019	$	217	$	(21	)	$	1,321,215