Fair Value Measurements

6 Months Ended

Jun. 30, 2013

Fair Value Measurements

Fair Value Measurements

4. Fair Value Measurements

We use a three-tier fair value hierarchy to prioritize the inputs used in our fair value measurements.  These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets for identical assets, which includes our money market funds and treasury securities classified as available-for-sale securities and an investment in equity securities in a publicly-held biotechnology company; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable, which includes our fixed income securities and commercial paper classified as available-for-sale securities; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. Our Level 3 investments include investments in the equity securities of publicly-held biotechnology companies for which we calculated a lack of marketability discount because there are restrictions on when we can trade the securities. The majority of our securities have been classified as Level 2. We obtain the fair value of our Level 2 investments from our custodian banks or from a professional pricing service.  We validate the fair value of our Level 2 investments by understanding the pricing model used by the custodian bank or professional pricing service provider and comparing that fair value to the fair value based on observable market prices.  During the three and six months ended June 30, 2013 and 2012 there were no transfers between our Level 1 and Level 2 investments. We use the end of reporting period method for determining transfers between levels.

We measure the following major security types at fair value on a recurring basis. We break down the inputs used to measure fair value for these assets at June 30, 2013 and December 31, 2012 as follows (in thousands):

	At June 30, 2013		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents (1)	$	287,759	$	277,272	$	10,487	$	—
Corporate debt securities (2)	231,216		—		231,216		—
Debt securities issued by U.S. government agencies (2)	28,837		—		28,837		—
Debt securities issued by the U.S. Treasury (2)	13,381		13,381		—		—
Debt securities issued by states of the United States and political subdivisions of the states (2)	20,778		—		20,778		—
Investment in Regulus Therapeutics Inc.	62,190		—		—		62,190
Equity securities (3)	1,434		1,434		—		—
Total	$	645,595	$	292,087	$	291,318	$	62,190

	At December 31, 2012		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents (1)	$	105,496	$	101,496	$	4,000	$	—
Corporate debt securities (2)	193,507		—		193,507		—
Debt securities issued by U.S. government agencies (2)	18,108		—		18,108		—
Debt securities issued by the U.S. Treasury (2)	13,452		13,452		—		—
Debt securities issued by states of the United States and political subdivisions of the states (2)	24,897		—		24,897		—
Investment in Regulus Therapeutics Inc.	33,622		—		—		33,622
Equity securities (3)	4,874		4,146		—		728
Total	$	393,956	$	119,094	$	240,512	$	34,350

(1) Included in cash and cash equivalents on our condensed consolidated balance sheet.

(2) Included in short-term investments on our condensed consolidated balance sheet.

(3) Included in other current assets on our condensed consolidated balance sheet.

We classified the fair value measurements of our investments in the equity securities of Regulus and Sarepta Therapeutics, Inc., or Sarepta, as Level 3.  We calculated a lack of marketability discount on the fair value of these investments because of trading restrictions on the securities. We consider the inputs we used to calculate the lack of marketability discount Level 3 inputs and, as a result, we categorized these investments as Level 3.  We determined the lack of marketability discount by using a Black-Scholes model to value a hypothetical put option to approximate the cost of hedging the stock until the restriction ends. In the first quarter of 2013, we sold all of the common stock of Sarepta that we owned resulting in a realized gain of $1.1 million. As of June 30, 2013, our Level 3 investments consisted of our investment in Regulus, with a gross fair value of $69.2 million less a lack of marketability discount of $7.0 million for a net carrying value of $62.2 million.  As of December 31, 2012, our Level 3 investments consisted of our investment in Regulus and Sarepta with a gross fair value of $44.4 million and $1.0 million, respectively, less a lack of marketability discount of $10.8 million and $296,000, respectively, for a net carrying value of $33.6 million and $728,000, respectively.

The following is a summary of our investments measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the six months ended June 30, 2013 (in thousands):

	InvestmentsValued UsingLevel 3 Inputs
Balance at December 31, 2012	$	34,350
Total gains and losses:
Included in gain on investments	(1,163		)
Included in accumulated other comprehensive income (loss)	29,043
Cost basis of shares sold	(40		)
Balance at June 30, 2013	$	62,190

Other Fair Value Disclosures

Our 2¾ percent convertible notes had a fair value of $357.2 million at June 30, 2013.  We determine the fair value of our 2¾ percent convertible notes based on quoted market prices for these notes, which is a Level 2 measurement.