Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2013

Summary of Significant Accounting Policies

Schedule of anti-dilutive shares

The following table presents anti-dilutive shares for the three and six months ended June 30, 2013 and 2012 (in thousands):

	Three Months Ended June 30,		Six Months Ended June 30,
	2013	2012	2013	2012
Weighted-average anti-dilutive shares related to:
Outstanding stock options	5,152	3,877	4,840	3,512
Restricted stock awards	979	1,033	938	983

Schedule of financial assets measured at fair value on a recurring basis

Financial assets measured at fair value on a recurring basis are summarized as follows (in thousands):

Description	Balance as of June 30, 2013		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	22,361	$	22,361	$	—	$	—
Marketable securities:
U.S. Government-sponsored enterprise obligations	53,793		—		53,793		—
Corporate debt securities	119,801		—		119,801		—
Commercial paper obligations	66,634		—		66,634		—
Foreign government bonds	33,418		—		33,418		—
Total	$	296,007	$	22,361	$	273,646	$	—

Description	Balance as of December 31, 2012		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	47,940	$	47,940	$	—	$	—
Marketable securities:
U.S. Government-sponsored enterprise obligations	51,225		—		51,225		—
Corporate debt securities	158,913		—		158,913		—
Commercial paper obligations	65,138		—		65,138		—
Foreign government bonds	12,337		—		12,337		—
Total	$	335,553	$	47,940	$	287,613	$	—

Schedule of reconciliation of cash, cash equivalents and marketable securities from amortized cost to fair value

The following tables summarize the Company’s cash, cash equivalents and marketable securities at June 30, 2013 and December 31, 2012 (in thousands):

As of June 30, 2013	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Cash and money market funds	$	26,514	$	—	$	—		$	26,514
U.S. Government-sponsored enterprise obligations
Due in one year or less	11,002		7		—			11,009
Due in two years or less	42,806		5		(27		)	42,784
Corporate debt securities
Due in one year or less	100,796		6		(47		)	100,755
Due in two years or less	19,070		1		(25		)	19,046
Commercial paper obligations due in one year or less	66,560		74		—			66,634
Foreign government bonds
Due in one year or less	31,788		29		(1		)	31,816
Due in two years or less	1,602		—		—			1,602
Total	$	300,138	$	122	$	(100	)	$	300,160
Reported as:
Cash and cash equivalents	$	26,514	$	—	$	—		$	26,514
Marketable securities	273,624		122		(100		)	273,646
Total	$	300,138	$	122	$	(100	)	$	300,160

As of December 31, 2012	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Cash and money market funds	$	52,990	$	—	$	—		$	52,990
U.S. Government-sponsored enterprise obligations
Due in one year or less	6,000		—		—			6,000
Due in two years or less	45,195		30		—			45,225
Corporate debt securities
Due in one year or less	76,500		19		(11		)	76,508
Due in two years or less	82,363		72		(30		)	82,405
Commercial paper obligations due in one year or less	65,104		34		—			65,138
Foreign government bonds
Due in one year or less	7,390		—		(1		)	7,389
Due in two years or less	4,950		—		(2		)	4,948
Total	$	340,492	$	155	$	(44	)	$	340,603
Reported as:
Cash and cash equivalents	$	52,990	$	—	$	—		$	52,990
Marketable securities	287,502		155		(44		)	287,613
Total	$	340,492	$	155	$	(44	)	$	340,603

Schedule of aggregate fair value and unrealized losses on marketable securities

The following table summarizes the aggregate fair value of these securities at June 30, 2013 and December 31, 2012 (in thousands):

	As of June 30, 2013					As of December 31, 2012
	Aggregate Fair Value		Unrealized Losses			Aggregate Fair Value		Unrealized Losses
U.S. Government-sponsored enterprise obligations	$	21,781	$	(27	)	$	—	$	—
Corporate debt securities	$	80,226	$	(72	)	$	83,529	$	(41	)
Foreign government bonds	$	8,282	$	(1	)	$	8,445	$	(3	)

Summary of changes in accumulated other comprehensive income (loss)

The following tables summarize the changes in accumulated other comprehensive income (loss) during the three and six months ended June 30, 2013 (in thousands):

	Unrealized Gains (Losses) on Securities Available for Sale
Balance as of March 31, 2013	$	46
Other comprehensive income (loss) before reclassifications	(24		)
Amounts reclassified from accumulated other comprehensive income (loss)	—
Net current period other comprehensive income (loss)	(24		)
Balance as of June 30, 2013	$	22

	Unrealized Gains (Losses) on Securities Available for Sale
Balance as of December 31, 2012	$	111
Other comprehensive income (loss) before reclassifications	(86		)
Amounts reclassified from accumulated other comprehensive income (loss)	(3		)
Net current period other comprehensive income (loss)	(89		)
Balance as of June 30, 2013	$	22