Fair Value Measurements

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

3. Fair Value Measurements

We invest in various short term, highly liquid financial instruments, which may include municipal debt securities, corporate bonds, U.S. agency securities and commercial paper. We value these instruments at fair value. The accounting guidance for fair value, among other things, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The framework for measuring fair value consists of a three-level valuation hierarchy that prioritizes the inputs to valuation techniques used to measure fair value based upon whether such inputs are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect market assumptions made by the reporting entity. The three-level hierarchy for the inputs to valuation techniques is briefly summarized as follows:  

Level 1—Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; 

Level 2—Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted 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 related assets or liabilities; and 

Level 3—Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data. 

An asset’s or liability’s fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Valuation techniques used need to maximize the use of observable inputs and minimize the use of unobservable inputs. 

Assets and liabilities measured at fair value are based on one or more of the following three valuation techniques: 

A. Market approach: Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.

B. Cost approach: Amount that would be required to replace the service capacity of an asset (replacement cost).

C. Income approach: Techniques to convert future amounts to a single present amount based upon market expectations, including present value techniques, option-pricing and excess earnings models.

The Company’s cash equivalents, which include money market funds, are classified as Level 1 because they are valued using quoted market prices. The Company’s marketable securities consist of securities and are generally classified as Level 2 because their value is based on valuations using significant inputs derived from or corroborated by observable market data. 

In certain cases where there is limited activity or less transparency around the inputs to valuation, securities are classified as Level 3. Level 3 liabilities consist of common stock warrant liability. 

Items Measured at Fair Value on a Recurring Basis 

The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): 

	December 31, 2018
	Level 1		Level 2		Level 3		Total
Financial Assets:
Money market funds	$	—	$	—	$	—	$	3
Corporate fixed income debt securities		—		—		—		—
Total	$	—	$	—	$	—	$	—
Financial Liabilities:
Common stock warrant liability (1)	$	—	$	—	$	—	$	—
Total	$	—	$	—	$	—	$	—

	December 31, 2017
	Level 1		Level 2		Level 3		Total
Financial Assets:
Money market funds	$	3	$	—	$	—	$	3
Corporate fixed income debt securities		—		5,023		—		5,023
Total	$	3	$	5,023	$	—	$	5,026
Financial Liabilities:
Common stock warrant liability (1)	$	—	$	—	$	—	$	—
Total	$	—	$	—	$	—	$	—

(1) The change in the fair value of the common stock warrant and convertible notes payable for the twelve months ended December 31, 2018 and 2017 was recorded as a decrease to other income (expense) and interest expense of $1 and $1, respectively, in the statements of operations and comprehensive loss.

Financial Instruments Not Carried at Fair Value 

The carrying amounts of the Company’s financial instruments, including accounts payable and accrued liabilities, approximate fair value due to their short maturities. The estimated fair value of the convertible notes and other notes, not recorded at fair value, are recorded at cost or amortized cost which was deemed to estimate fair value.