Investments (Tables)

6 Months Ended

Jun. 30, 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 June 30, 2013:

One year or less	57	%
After one year but within two years	26	%
After two years but within three years	17	%
Total	100	%

Summary of investments

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

								Other-Than-
								Temporary
	Amortized		Unrealized					Impairment		Estimated
June 30, 2013	Cost		Gains		Losses			Loss		Fair Value
Available-for-sale securities:
Corporate debt securities (1)	$	134,045	$	60	$	(88	)	$	—	$	134,017
Debt securities issued by U.S. government agencies (1)	23,887		—		(85		)	—		23,802
Debt securities issued by the U.S. Treasury	5,023		4		—			—		5,027
Debt securities issued by states of the United States and political subdivisions of the states	11,989		35		—			—		12,024
Total securities with a maturity of one year or less	174,944		99		(173		)	—		174,870
Corporate debt securities	103,219		23		(546		)	—		102,696
Debt securities issued by U.S. government agencies	10,002		25		(3		)	—		10,024
Debt securities issued by the U.S. Treasury	8,340		14		—			—		8,354
Debt securities issued by states of the United States and political subdivisions of the states	8,771		5		(22		)	—		8,754
Total securities with a maturity of more than one year	130,332		67		(571		)	—		129,828
Total	$	305,276	$	166	$	(744	)	$	—	$	304,698

							Other-Than-
							Temporary
	Cost		Unrealized				Impairment			Estimated
June 30, 2013	Basis		Gains		Losses		Loss			Fair Value
Equity securities:
Regulus Therapeutics Inc.	$	15,525	$	46,665	$	—	$	—		$	62,190
Current portion (included in Other current assets)	1,538		776		—		(880		)	1,434
Long-term portion (included in Deposits and other assets)	625		—		—		—			625
Total	$	17,688	$	47,441	$	—	$	(880	)	$	64,249

								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
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
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 June 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	85	$	152,051	$	(634	)
Debt securities issued by U.S. government agencies	7	25,342		(88		)
Debt securities issued by states of the United States and political subdivisions of the states	6	7,823		(22		)
Total temporarily impaired securities	98	$	185,216	$	(744	)