Investments (Tables)

3 Months Ended

Mar. 31, 2013

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 March 31, 2013:

One year or less	47	%
After one year but within two years	41	%
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
March 31, 2013	Cost		Gains		Losses			Loss		Fair Value
Short-term investments:
Corporate debt securities	$	97,983	$	59	$	(29	)	$	—	$	98,013
Debt securities issued by U.S. government agencies	9,932		1		(46		)	—		9,887
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	15,549		55		(11		)	—		15,593
Total securities with a maturity of one year or less	124,464		116		(86		)	—		124,494
Corporate debt securities	107,131		110		(156		)	—		107,085
Debt securities issued by U.S. government agencies	15,020		35		(3		)	—		15,052
Debt securities issued by the U.S. Treasury	12,393		30		—			—		12,423
Debt securities issued by states of the United States and political subdivisions of the states	5,203		7		(3		)	—		5,207
Total securities with a maturity of more than one year	139,747		182		(162		)	—		139,767
Subtotal	$	264,211	$	298	$	(248	)	$	—	$	264,261

								Other-Than-
								Temporary
	Cost		Unrealized					Impairment			Estimated
March  31, 2013	Basis		Gains		Losses			Loss			Fair Value
Equity securities:
Current portion (Regulus Therapeutics Inc.)	$	15,525	$	29,338	$	—		$	—		$	44,863
Current portion (included in Other current assets)	1,538		1,961		—			(880		)	2,619
Long-term portion (included in Deposits and other assets)	625		—		—			—			625
Subtotal	$	17,688	$	31,299	$	—		$	(880	)	$	48,107
	$	281,899	$	31,597	$	(248	)	$	(880	)	$	312,368

								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

Schedule of investments temporarily impaired

Investments we considered to be temporarily impaired at March 31, 2013 were as follows (in thousands):

		Less than 12 months of temporary impairment
	Number of Investments	Estimated Fair Value		Unrealized Losses
Corporate debt securities	70	$	95,606	$	(185	)
Debt securities issued by U.S. government agencies	4	13,885		(49		)
Debt securities issued by states of the United States and political subdivisions of the states	3	4,537		(14		)
Total temporarily impaired securities	77	$	114,028	$	(248	)