Investments (Tables)

12 Months Ended

Dec. 31, 2012

Investments

Summary of contract maturity of available-for-sale securities

One year or less	56	%
After one year but within two years	32	%
After two years but within three years	12	%
Total	100	%

Summary of investments

The following is a summary of our investments (in thousands):

								Other-Than-
								Temporary
	Amortized		Unrealized					Impairment		Estimated
December 31, 2012	Cost		Gains		Losses			Loss		Fair Value
Short-term investments:
Corporate debt securities	$	113,249	$	81	$	(9	)	$	—	$	113,321
Debt securities issued by U.S. government agencies	10,100		2		(66		)	—		10,036
Debt securities issued by the U.S. Treasury	1,000		1		—			—		1,001
Debt securities issued by states of the United States and political subdivisions of the states	16,560		18		(2		)	—		16,576
Total securities with a maturity of one year or less	140,909		102		(77		)	—		140,934
Corporate debt securities	80,166		112		(92		)	—		80,186
Debt securities issued by U.S. government agencies	8,034		38		—			—		8,072
Debt securities issued by the U.S. Treasury	12,424		27		—			—		12,451
Debt securities issued by states of the United States and political subdivisions of the states	8,306		31		(16		)	—		8,321
Total securities with a maturity of more than one year	108,930		208		(108		)	—		109,030
Subtotal	$	249,839	$	310	$	(185	)	$	—	$	249,964

								Other-Than-
								Temporary
	Cost		Unrealized					Impairment			Estimated
December 31, 2012	Basis		Gains		Losses			Loss			Fair Value
Equity securities:
Current portion (Regulus Therapeutics Inc.)	$	15,526	$	18,096	$	—		$	—		$	33,622
Current portion (included in Other current assets)		1,579		4,175		—			(880	)		4,874
Long-term portion (included in Deposits and other assets)	625		—		—			—			625
Subtotal	$	17,730	$	22,271	$	—		$	(880	)	$	39,121
	$	267,569	$	22,581	$	(185	)	$	(880	)	$	289,085

	Amortized		Unrealized					Impairment		Estimated
December 31, 2011	Cost		Gains		Losses			Loss		Fair Value
Short-term investments:
Corporate debt securities	$	109,842	$	13	$	(255	)	$	—	$	109,600
Debt securities issued by U.S. government agencies	53,723		35		(5		)	—		53,753
Debt securities issued by the U.S. Treasury	2,353		3		—			—		2,356
Debt securities issued by states of the United States and political subdivisions of the states	16,141		4		(3		)	—		16,142
Total securities with a maturity of one year or less	182,059		55		(263		)	—		181,851
Corporate debt securities	57,632		21		(331		)	—		57,322
Debt securities issued by U.S. government agencies	26,754		—		(67		)	—		26,687
Debt securities issued by states of the United States and political subdivisions of the states	12,331		19		(23		)	—		12,327
Total securities with a maturity of more than one year	96,717		40		(421		)	—		96,336
Subtotal	$	278,776	$	95	$	(684	)	$	—	$	278,187

								Other-Than-
								Temporary
	Cost		Unrealized					Impairment			Estimated
December 31, 2011	Basis		Gains		Losses			Loss			Fair Value
Equity securities:
Current portion (included in Other current assets)	$	1,538	$	624	$	—		$	(880	)	$	1,282
Long-term portion (included in Deposits and other assets)	625		—		—			—			625
Subtotal	$	2,163	$	624	$	—		$	(880	)	$	1,907
	$	280,939	$	719	$	(684	)	$	(880	)	$	280,094

Schedule of investments temporarily impaired

Investments we consider to be temporarily impaired at December 31, 2012 are as follows (in thousands):

		Less than 12 months of temporary impairment
	Number of Investments	Estimated Fair Value		Unrealized Losses
Corporate debt securities	39	$	57,997	$	(101	)
Debt securities issued by U.S. government agencies	1	5,029		(66		)
Debt securities issued by states of the United States and political subdivisions of the states	4	9,716		(18		)
Total temporarily impaired securities	44	$	72,742	$	(185	)