The authoritative guidance on fair value measurements establishes a framework with respect to measuring assets and liabilities at fair value on a recurring basis and non-recurring basis. Under the framework, fair value is defined as the exit price, or the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants, as of the measurement date. The framework also establishes a three-tier hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs market participants would use in valuing the asset or liability and are developed based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the factors market participants would use in valuing the asset or liability and are developed based on the best information available in the circumstances. The hierarchy consists of the following three levels:

The following tables present information about the Company’s financial assets measured at fair value on a recurring basis, based on the three-tier fair value hierarchy:

	March 31, 2020
	Total		Level 1		Level 2		Level 3
	(in thousands)
Marketable securities and cash equivalents:
Corporate debt securities	$	60,319	$	—	$	60,319	$	—
U.S. government agency securities		1,003		—		1,003		—
Money market accounts		3,943		3,943		—		—
Total marketable securities	$	65,265	$	3,943	$	61,322	$	—

	December 31, 2019
	Total		Level 1		Level 2		Level 3
	(in thousands)
Marketable securities and cash equivalents:
Corporate debt securities	$	59,950	$	—	$	59,950	$	—
Money market accounts		4,700		4,700		—		—
Total marketable securities and cash equivalents	$	64,650	$	4,700	$	59,950	$	—

The Company’s Level 1 assets include money market instruments and are valued based upon observable market prices. Level 2 assets consist of U.S. government agency securities and corporate debt securities. Level 2 securities are valued based upon observable inputs that include reported trades, broker/dealer quotes, bids and offers. As of March 31, 2020, the Company had no investments that were measured using unobservable (Level 3) inputs.

There were no transfers between fair value measurement levels during the first quarter of 2020.

Gross unrealized gains or losses for cash equivalents and marketable securities as of March 31, 2020 were not material. As of March 31, 2020, there were no unrealized losses for securities in an unrealized loss position for more than 12 months. During the three months ended March 31, 2020, the Company did not recognize other-than-temporary impairment losses related to its marketable securities.