Investments (Tables)

6 Months Ended

Jun. 30, 2011

Investments

Summary of contract maturity of available-for-sale securities

The following table summarizes the contract maturity of the available-for-sale securities we held as of June 30, 2011:

One year or less	76	%
After one year but within two years	20	%
After two years but within three years	4	%
Total	100	%

Summary of investments

	Amortized		Unrealized					Other-Than- Temporary Impairment			Estimated
June 30, 2011	Cost		Gains		Losses			Loss			Fair Value
Short-term investments:
Corporate debt securities	$	167,417	$	196	$	(51	)	$	—		$	167,562
Debt securities issued by U.S. government agencies	57,128		25		(8		)	—			57,145
Debt securities issued by the U.S. Treasury	6,513		10		—			—			6,523
Debt securities issued by states of the United States and political subdivisions of the states	7,401		—		—			—			7,401
Total securities with a maturity of one year or less	238,459		231		(59		)	—			238,631
Corporate debt securities	57,591		140		(57		)	—			57,674
Debt securities issued by U.S. government agencies	10,117		13		—			—			10,130
Debt securities issued by states of the United States and political subdivisions of the states	3,730		—		(3		)	—			3,727
Total securities with a maturity of more than one year	71,438		153		(60		)	—			71,531
Subtotal	$	309,897	$	384	$	(119	)	$	—		$	310,162
Equity securities:
Current portion (included in Other current assets)	$	1,538	$	939	$	—		$	(880	)	$	1,597
Long-term portion (included in Deposits and other assets)	625		—		—			—			625
Subtotal	$	2,163	$	939	$	—		$	(880	)	$	2,222
	$	312,060	$	1,323	$	(119	)	$	(880	)	$	312,384

	Amortized		Unrealized					Other-Than- Temporary Impairment			Estimated
December 31, 2010	Cost		Gains		Losses			Loss			Fair Value
Short-term investments:
Corporate debt securities	$	196,010	$	294	$	(41	)	$	—		$	196,263
Debt securities issued by U.S. government agencies	119,890		53		(34		)	—			119,909
Debt securities issued by the U.S. Treasury	24,030		10		—			—			24,040
Debt securities issued by states of the United States and political subdivisions of the states	6,989		3		—			—			6,992
Total securities with a maturity of one year or less	346,919		360		(75		)	—			347,204
Corporate debt securities	47,842		167		(44		)	—			47,965
Debt securities issued by U.S. government agencies	7,139		4		(11		)	—			7,132
Total securities with a maturity of more than one year	54,981		171		(55		)	—			55,097
Subtotal	$	401,900	$	531	$	(130	)	$	—		$	402,301
Equity securities:
Current portion (included in Other current assets)	$	1,538	$	1,353	$	—		$	(880	)	$	2,011
Long-term portion (included in Deposits and other assets)	625		—		—			—			625
Subtotal	$	2,163	$	1,353	$	—		$	(880	)	$	2,636
	$	404,063	$	1,884	$	(130	)	$	(880	)	$	404,937

Schedule of investments temporarily impaired

		Less than 12 months of temporary impairment
	Number of Investments	Estimated Fair Value		Unrealized Losses
Corporate debt securities	45	$	97,370	$	(108	)
Debt securities issued by U.S. government agencies	4	11,541		(8		)
Debt securities issued by states of the United States and political subdivisions of the states	3	3,733		(3		)
Total temporarily impaired securities	52	$	112,644	$	(119	)