Note 3 - Fair Value Measurements

12 Months Ended

Dec. 31, 2018

3.	Fair Value Measurements

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The FASB Accounting Standards Codification (“ASC”) Topic

820,

Fair Value Measurements & Disclosures

, establishes a fair value hierarchy which prioritizes the inputs used in measuring fair value as follows:

•

Level

— Observable inputs such as quoted prices in active markets for identical assets or liabilities.

•

Level

— Inputs other than Level

that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices 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

— Unobservable inputs that are supported by little or

market activity and that are significant to the fair value of the assets or liabilities.

We measure cash equivalents and short-term investments at fair value on a recurring basis. The fair values of these such assets were as follows (in thousands):

			Fair Value Measurements at Reporting Date Using
			Quoted Prices in		Significant
			Active Markets		Other		Significant
	Balance at		for Identical		Observable		Unobservable
	December 31,		Assets		Inputs		Inputs
	2018		(Level 1)		(Level 2)		(Level 3)
Money market funds	$	13,874	$	13,874	$	—	$	—
U.S. treasury bills and government agency obligations		59,741		59,741		—		—
U.S. corporate debt securities		59,087		—		59,087		—
Foreign corporate debt securities		5,046		—		5,046		—
U.S. commercial paper		61,885		—		61,885		—
Foreign commercial paper		123,861		—		123,861		—
Total	$	323,494	$	73,615	$	249,879	$	—

			Fair Value Measurements at Reporting Date Using
			Quoted Prices in		Significant
			Active Markets		Other		Significant
	Balance at		for Identical		Observable		Unobservable
	December 31 ,		Assets		Inputs		Inputs
	2017		(Level 1)		(Level 2)		(Level 3)
Money market funds	$	91,386	$	91,386	$	—	$	—
U.S. corporate debt securities		17,520		—		17,520		—
U.S. commercial paper		39,863		—		39,863		—
Foreign commercial paper		19,854		—		19,854		—
Total	$	168,623	$	91,386	$	77,237	$	—

We have

not

transferred any investment securities between the

three

levels of the fair value hierarchy.

As of

December 31, 2018,

cash equivalents included

$9.1

million of available-for-sale securities with contractual maturities of

three

months or less, and short-term investments included

$300.5

million of available-for-sale securities with contractual maturities of

three

months to

one

year. As of

December 31, 2017,

cash equivalents included

$49.4

million of available-for-sale securities with contractual maturities of

three

months or less, and short-term investments included

$27.8

million of available-for-sale securities with contractual maturities of

three

months to

one

year. The money market funds as of

December 31, 2018

and

2017

are included in cash and cash equivalents on the consolidated balance sheets.

Unrealized gains and losses associated with our investments are reported in accumulated other comprehensive loss. For the year ended

December 31, 2018,

we recorded

$77,000

in net unrealized losses associated with our short-term investments. For the years ended

December 31, 2017

and

2016,

we recorded

$7,000

and

$23,000,

respectively, in net unrealized gains associated with our short-term investments.

Realized gains and losses associated with our investments, if any, are reported in the statements of operations and comprehensive loss. We did

not

recognize any realized gains or losses during the years ended

December 31, 2018,

2017

and

2016.

- 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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