Investments (Tables)

9 Months Ended

Sep. 30, 2011

Investments

Summary of contract maturity of available-for-sale securities

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
September 30, 2011	Cost		Gains		Losses			Loss			Fair Value
Short-term investments:
Corporate debt securities	$	149,296	$	28	$	(380	)	$	—		$	148,944
Debt securities issued by U.S. government agencies	65,707		22		(9		)	—			65,720
Debt securities issued by the U.S. Treasury	4,506		6		—			—			4,512
Debt securities issued by states of the United States and political subdivisions of the states	15,451		3		—			—			15,454
Total securities with a maturity of one year or less	234,960		59		(389		)	—			234,630
Corporate debt securities	59,430		35		(412		)	—			59,053
Debt securities issued by U.S. government agencies	12,263		6		(157		)	—			12,112
Debt securities issued by states of the United States and political subdivisions of the states	3,706		1		(2		)	—			3,705
Total securities with a maturity of more than one year	75,399		42		(571		)	—			74,870
Subtotal	$	310,359	$	101	$	(960	)	$	—		$	309,500
Equity securities:
Current portion (included in Other current assets)	$	1,538	$	511	$	—		$	(880	)	$	1,169
Long-term portion (included in Deposits and other assets)	625		—		—			—			625
Subtotal	$	2,163	$	511	$	—		$	(880	)	$	1,794
	$	312,522	$	612	$	(960	)	$	(880	)	$	311,294

	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	66	$	137,205	$	(792	)
Debt securities issued by U.S. government agencies	9	28,565		(166		)
Debt securities issued by states of the United States and political subdivisions of the states	2	2,405		(2		)
Total temporarily impaired securities	77	$	168,175	$	(960	)