FAIR VALUE MEASUREMENTS

12 Months Ended

Dec. 31, 2014

4.	FAIR VALUE MEASUREMENTS

The following tables present information about our assets that are measured at fair value on a recurring basis at December 31, 2014 and 2013, and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value, in thousands:


Description	At December 31, 2014		Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents	$	56,203	$	56,203	$	—	$	—
Marketable securities (fixed income):
Certificates of deposit		24,300		—		24,300		—
Commercial paper		40,796		—		40,796		—
Corporate notes		662,545		—		662,545		—
Municipal debt securities		9,005		—		9,005		—
U.S. government-sponsored enterprise securities		64,856		—		64,856		—
U.S. treasury securities		5,248		—		5,248		—
Marketable securities (Regulus equity holdings)		94,583		94,583		—		—

Total	$	957,536	$	150,786	$	806,750	$	—


Description	At December 31, 2013		Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents	$	32,571	$	32,571	$	—	$	—
Marketable securities (fixed income):
Corporate notes		228,462		—		228,462		—
U.S. government-sponsored enterprise securities		56,863		—		56,863		—
Commercial paper		11,978		—		11,978		—
Marketable securities (Regulus equity holdings)		45,452		45,452		—		—

Total	$	375,326	$	78,023	$	297,303	$	—

For the year ended December 31, 2014, there were no transfers between Level 1 and Level 2 financial assets. For the year ended December 31, 2013, we transferred $45.5 million of marketable securities (equity holdings in Regulus) from Level 2 to Level 1 due to the increased volume in average daily trading on the NASDAQ stock market for these instruments. The carrying amounts reflected in our consolidated balance sheets for cash, billed and unbilled collaboration receivables, other current assets, accounts payable and accrued expenses approximate fair value due to their short-term maturities.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

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