Fair value of financial instruments

9 Months Ended

Sep. 30, 2013

The Company measures certain financial instruments at fair value on a recurring basis. The Company uses a three-tier fair value hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value:

Level 1 valuations are based on quoted prices in active markets for identical assets or liabilities.

Level 2 valuations are based on inputs that are observable, either directly or indirectly, other than quoted prices included within Level 1. Such inputs used in determining fair value for Level 2 valuations include quoted prices in active markets for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3 valuations are based on information that is unobservable and significant to the overall fair value measurement.

All of the Company’s cash equivalents and short-term investments are classified within Level 1 or Level 2.

The following table presents information about the Company’s financial instruments that are measured at fair value as of September 30, 2013 and indicates the fair value hierarchy of the valuation (in thousands):



	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Description
Cash equivalents:
Money market mutual funds	$	142,968	$	142,968	$	—
Total cash equivalents	142,968		142,968		—
Short-term investments:
Corporate bonds	39,555		—		39,555
U.S. agency securities	32,274		—		32,274
Asset-backed securities	13,957		—		13,957
U.S. Treasury securities	17,818		—		17,818
Total short-term investments	103,604		—		103,604
Cash equivalents and short-term investments	$	246,572	$	142,968	$	103,604

The following table presents information about the Company’s financial instruments that are measured at fair value as of December 31, 2012 and indicates the fair value hierarchy of the valuation (in thousands):



	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Description
Cash equivalents:
Money market mutual funds	$	17,000	$	17,000	$	—
Total cash equivalents	17,000		17,000		—
Short-term investments:
Corporate bonds	13,377		—		13,377
U.S. agency securities	11,283		—		11,283
Asset-backed securities	4,666		—		4,666
U.S. Treasury securities	3,548		—		3,548
Total short-term investments	32,874		—		32,874
Cash equivalents and short-term investments	$	49,874	$	17,000	$	32,874

The convertible notes issued by the Company in August 2013 are shown in the accompanying consolidated balance sheets at their original issuance value, net of unamortized discount, and are not marked to market each period. The fair value of the convertible notes approximates the notes carrying value as of September 30, 2013. The fair value of the convertible notes was determined using quoted market prices for similar securities, which, due to limited trading activity, are considered Level 2 in the fair value hierarchy.

The Company did not have any financial liabilities measured at fair value as of December 31, 2012.

- 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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