FAIR VALUE MEASUREMENTS

3 Months Ended

Mar. 31, 2019

6. FAIR VALUE MEASUREMENTS

The following tables present information about our assets that are measured at fair value on a recurring basis at March 31, 2019 and December 31, 2018, and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value, in thousands:

Description	At March 31, 2019		Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents:
U.S. treasury securities	$	530,231	$	—	$	530,231	$	—
Money market funds		98,236		98,236		—		—
Marketable debt securities:
Certificates of deposit		3,000		—		3,000		—
Commercial paper		34,394		—		34,394		—
Corporate notes		113,253		—		113,253		—
U.S. government-sponsored enterprise securities		2,496		—		2,496		—
U.S. treasury securities		366,435		—		366,435		—
Restricted cash (money market funds)		1,478		1,478		—		—
Total	$	1,149,523	$	99,714	$	1,049,809	$	—

Description	At December 31, 2018		Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents:
U.S. treasury securities	$	221,281	$	—	$	221,281	$	—
Money market funds		102,445		102,445		—		—
Marketable debt securities:
Certificates of deposit		8,951		—		8,951		—
Commercial paper		57,197		—		57,197		—
Corporate notes		232,410		—		232,410		—
U.S. government-sponsored enterprise securities		39,018		—		39,018		—
U.S. treasury securities		325,227		—		325,227		—
Marketable equity securities		1,206		1,206		—		—
Restricted cash (money market funds)		1,477		1,477		—		—
Total	$	989,212	$	105,128	$	884,084	$	—

During the three months ended March 31, 2019 and 2018, there were no transfers between Level 1 and Level 2 financial assets. The carrying amounts reflected in our condensed consolidated balance sheets for cash, accounts receivable, net, other current assets, accounts payable and accrued expenses approximate fair value due to their short-term maturities. The fair value of our long-term debt at March 31, 2019 and December 31, 2018, computed pursuant to a discounted cash flow technique using a market interest rate, was $30.1 million and is considered a Level 3 fair value measurement. The effective interest rate reflects the current market rate.

- 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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