Fair Value Measures

6 Months Ended

Jun. 30, 2011

Fair Value Measures [Abstract]

Fair Value Measures

2. Fair Value Measures

The Company measures its investments at fair value under GAAP. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value hierarchy of the Company's financial assets carried at fair value and measured on a recurring basis is as follows (amounts in thousands):

			Fair value measurements at the reporting date using
	June 30, 2011		Quoted prices in active markets using identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Cash equivalents
Money market	$	72	$	—	$	72	$	—
Commercial paper		51,967		—		51,967		—
Total		52,039		—		52,039		—
Available-for-sale securities
U.S. government securities		139,065		—		139,065		—
Commercial paper		46,573		—		46,573		—
Taxable municipal bonds		7,066		—		7,066		—
Total		192,704		—		192,704		—
Total	$	244,743	$	—	$	244,743	$	—
			Fair value measurements at the reporting date using
	December 31, 2010		Quoted prices in active markets using identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Cash equivalents
Money market funds	$	31	$	—	$	31	$	—
Commercial paper		87,902		—		87,902		—
Taxable municipal bonds		12,096		—		12,096		—
Total		100,029		—		100,029		—
Available-for-sale securities
U.S. government securities		90,850		—		90,850		—
Taxable municipal bonds		7,241		—		7,241		—
Total		98,091		—		98,091		—
Total	$	198,120	$	—	$	198,120	$	—

Maturity information was as follows for investments classified as available-for-sale at June 30, 2011 (in thousands):

	Amortized Cost		Gross unrealized gains		Gross unrealized losses			Fair value
Within one year	$	192,695	$	49	$	(40	)	$	192,704
Greater than one year		—		—		—			—
Total	$	192,695	$	49	$	(40	)	$	192,704

Maturity information was as follows for investments classified as available-for-sale at December 31, 2010 (in thousands):

	Amortized Cost		Gross unrealized gains		Gross unrealized losses			Fair value
Within one year	$	98,091	$	13	$	(13	)	$	98,091
Greater than one year		—		—		—			—
Total	$	98,091	$	13	$	(13	)	$	98,091

In the six months ended June 30, 2011 and at December 31, 2010, the Company did not measure the fair value of any of its assets or liabilities other than cash equivalents and available-for-sale investments. The Company's management considers the carrying values of accounts receivable, other receivables, prepaid expenses and other current assets, accounts payable, accrued expenses and other current liabilities to approximate fair values primarily due to their short-term nature.