Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2013

Summary of Significant Accounting Policies

Schedule of anti-dilutive shares

The following table presents anti-dilutive shares for the three months ended March 31, 2013 and March 31, 2012 (in thousands):

	March 31, 2013	March 31, 2012
Weighted-average anti-dilutive shares related to:
Outstanding stock options	4,526	3,148
Restricted stock awards	895	933

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 March 31, 2013		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	38,848	$	38,848	$	—	$	—
Marketable securities:
U.S. Government-sponsored enterprise obligations	67,788		—		67,788		—
Corporate debt securities	145,526		—		145,526		—
Commercial paper obligations	57,633		—		57,633		—
Foreign government bonds	9,969		—		9,969		—
Total	$	319,764	$	38,848	$	280,916	$	—

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 March 31, 2013 and December 31, 2012 (in thousands):

As of March 31, 2013	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Cash and money market funds	$	43,288	$	—	$	—		$	43,288
U.S. Government-sponsored enterprise obligations
Due in one year or less	4,253		3		—			4,256
Due in two years or less	63,526		18		(12		)	63,532
Corporate debt securities
Due in one year or less	108,993		33		(39		)	108,987
Due in two years or less	36,541		27		(29		)	36,539
Commercial paper obligations due in one year or less	57,588		45		—			57,633
Foreign government bonds
Due in one year or less	8,366		1		(1		)	8,366
Due in two years or less	1,603		—		—			1,603
Total	$	324,158	$	127	$	(81	)	$	324,204
Reported as:
Cash and cash equivalents	$	43,288	$	—	$	—		$	43,288
Marketable securities	280,870		127		(81		)	280,916
Total	$	324,158	$	127	$	(81	)	$	324,204

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 March 31, 2013 and December 31, 2012 (in thousands):

	As of March 31, 2013					As of December 31, 2012
	Aggregate Fair Value		Unrealized Losses			Aggregate Fair Value		Unrealized Losses
U.S. Government-sponsored enterprise obligations	$	39,822	$	(12	)	$	—	$	—
Corporate debt securities	$	84,402	$	(68	)	$	83,529	$	(41	)
Foreign government bonds	$	6,657	$	(1	)	$	8,445	$	(3	)

Summary of changes in accumulated other comprehensive income (loss)

The following table summarizes the changes in accumulated other comprehensive income (loss) (in thousands):

	Unrealized Gains (Losses) on Securities Available for Sale
Balance as of December 31, 2012	$	111
Other comprehensive income (loss) before reclassifications	(62		)
Amounts reclassified from accumulated other comprehensive income (loss)	(3		)
Net current period other comprehensive income (loss)	(65		)
Balance as of March 31, 2013	$	46