Investments (Tables)

9 Months Ended

Sep. 30, 2013

Investments

Summary of contract maturity of available-for-sale securities

One year or less	39	%
After one year but within two years	42	%
After two years but within three years	19	%
Total	100	%

Summary of investments

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

								Other-Than-
								Temporary
	Amortized		Unrealized					Impairment			Estimated
September 30, 2013	Cost		Gains		Losses			Loss			Fair Value
Available-for-sale securities:
Corporate debt securities (1)	$	119,472	$	65	$	(44	)	$	—		$	119,493
Debt securities issued by U.S. government agencies (1)	19,341		11		(27		)	—			19,325
Debt securities issued by the U.S. Treasury	7,257		10		—			—			7,267
Debt securities issued by states of the United States and political subdivisions of the states	16,110		19		(16		)	—			16,113
Total securities with a maturity of one year or less	162,180		105		(87		)	—			162,198
Corporate debt securities	220,494		87		(507		)	—			220,074
Debt securities issued by U.S. government agencies	17,479		22		(6		)	—			17,495
Debt securities issued by the U.S. Treasury	9,075		22		—			—			9,097
Debt securities issued by states of the United States and political subdivisions of the states	7,202		25		(1		)	—			7,226
Total securities with a maturity of more than one year	254,250		156		(514		)	—			253,892
Total	$	416,430	$	261	$	(601	)	$	—		$	416,090
								Other-Than-
								Temporary
	Cost		Unrealized					Impairment			Estimated
September 30, 2013	Basis		Gains		Losses			Loss			Fair Value
Equity securities:
Regulus Therapeutics Inc.	$	15,526	$	49,478	$	—		$	—		$	65,004
Securities included in other current assets	1,538		1,174		—			(880		)	1,832
Securities included in deposits and other assets	625		—		—			—			625
Total	$	17,689	$	50,652	$	—		$	(880	)	$	67,461

								Other-Than-
								Temporary
	Amortized		Unrealized					Impairment			Estimated
December 31, 2012	Cost		Gains		Losses			Loss			Fair Value
Available-for-sale securities:
Corporate debt securities (1)	$	115,249	$	81	$	(9	)	$	—		$	115,321
Debt securities issued by U.S. government agencies (1)	12,100		2		(66		)	—			12,036
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	144,909		102		(77		)	—			144,934
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
Total	$	253,839	$	310	$	(185	)	$	—		$	253,964
								Other-Than-
								Temporary
	Cost		Unrealized					Impairment			Estimated
December 31, 2012	Basis		Gains		Losses			Loss			Fair Value
Equity securities:
Regulus Therapeutics Inc.	$	15,526	$	18,096	$	—		$	—		$	33,622
Securities included in other current assets	1,579		4,175		—			(880		)	4,874
Securities included in deposits and other assets	625		—		—			—			625
Total	$	17,730	$	22,271	$	—		$	(880	)	$	39,121

(1) Includes investments classified as cash equivalents on our condensed consolidated balance sheet.

Schedule of investments temporarily impaired

Investments we considered to be temporarily impaired at September 30, 2013 were as follows (in thousands):

		Less than 12 months of temporary impairment
	Number of Investments	Estimated Fair Value		Unrealized Losses
Corporate debt securities	137	$	218,610	$	(551	)
Debt securities issued by U.S. government agencies	4	19,976		(33		)
Debt securities issued by states of the United States and political subdivisions of the states	4	5,104		(17		)
Total temporarily impaired securities	145	$	243,690	$	(601	)