Fair Value Measurements

	Fair Value Measurement as of March 31, 2020
	Level 1		Level 2		Level 3		Total
Financial Assets:
Cash equivalents:
Money market funds	$	138,733	$	—	$	—	$	138,733
Commercial paper		—		27,478		—		27,478
U.S. government treasury securities		—		12,000		—		12,000
Certificates of deposit		—		3,202		—		3,202
Marketable Securities:
Corporate debt securities		—		319,499		—		319,499
U.S. government agencies		—		14,972		—		14,972
Certificates of deposit		—		39,919		—		39,919
U.S. government treasury securities		—		107,054		—		107,054
Commercial paper		—		118,940		—		118,940
Total financial assets	$	138,733	$	643,064	$	—	$	781,797

	Fair Value Measurement as of December 31, 2019
	Level 1		Level 2		Level 3		Total
Financial Assets:
Cash equivalents:
Money market funds	$	588,762	$	—	$	—	$	588,762
Marketable Securities:
Corporate debt securities		—		80,417		—		80,417
U.S. government treasury securities		—		72,473		—		72,473
Commercial paper		—		23,784		—		23,784
Total financial assets	$	588,762	$	176,674	$	—	$	765,436

The Company classifies its highly liquid money market funds within Level 1 of the fair value hierarchy because they are valued based on quoted market prices in active markets. The Company classifies its commercial paper, corporate debt securities, U.S. government agencies, certificates of deposit, and U.S. government treasury securities within Level 2 because they are valued using inputs other than quoted prices that are directly or indirectly observable in the market, including readily available pricing sources for the identical underlying security which may not be actively traded.

- 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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