8. FAIR VALUE MEASUREMENTS

In accordance with the provisions of fair value accounting, a fair value measurement assumes that a transaction to sell an asset or transfer a liability occurs in the principal market for the asset or liability or, in the absence of a principal market, the most advantageous market for the asset or liability and defines fair value based upon an exit price model.

The fair value measurement guidance establishes a fair value hierarchy which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The guidance describes three levels of inputs that may be used to measure fair value:


Level 1		Quoted prices in active markets for identical assets or liabilities as of the reporting date. Active markets are those in which transactions for the asset and liability occur in sufficient frequency and volume to provide pricing information on an ongoing basis. Level 1 assets and liabilities include money market funds, debt and equity securities and derivative contracts that are traded in an active exchange market.

Level 2		Observable inputs other than Level 1 prices, 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 2 assets and liabilities include debt securities with quoted prices that are traded less frequently than exchange‑traded instruments and derivative contracts whose value is determined using a pricing model with inputs that are observable in the market or can be derived principally from or corroborated by observable market data. This category generally includes corporate obligations and non‑exchange traded derivative contracts.

Level 3		Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments and intangible assets that have been impaired whose value is determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation.

Assets and liabilities of the Company measured at fair value on a recurring basis as of March 31, 2019 and December 31, 2018 are summarized as follows (in thousands):


			March 31, 2019
			Significant Other
	Quoted Prices in		Observable		Unobservable
	Active Markets		Inputs		Inputs
Description	(Level 1)		(Level 2)		(Level 3)		Total
Certificates of deposit	$	—	$	380	$	—	$	380
Money market funds		2,615		—		—		2,615
Short term investments		5,280		—		—		5,280
Other investments		—		—		10,000		10,000
Commercial paper		—		13,975		—		13,975
Interest rate swap		—		70		—		70
Total assets and liabilities measured at fair value	$	7,895	$	14,425	$	10,000	$	32,320


	December 31, 2018
			Significant Other
	Quoted Prices in		Observable
	Active Markets		Inputs
Description	(Level 1)		(Level 2)		Total
Certificates of deposit	$	—	$	380	$	380
Money market funds		2,266		—		2,266
Short term investments		393		—		393
Commercial paper		—		13,972		13,972
Interest rate swap		—		140		140
Total assets and liabilities measured at fair value	$	2,659	$	14,492	$	17,151

Certificate of Deposit

As of March 31, 2019 and December 31, 2018, this asset class consisted of a time deposit at a financial institution denominated in US dollars. The asset class is classified within Level 2 of the fair value hierarchy because the fair value was based on observable market data.

Money Market Funds

As of March 31, 2019 and December 31, 2018, this asset class consisted of a money market portfolio that comprises Federal government and US Treasury securities. The asset class is classified within Level 1 of the fair value hierarchy because its underlying investments are valued using quoted market prices in active markets for identical assets.

Short Term Investments and Commercial Paper

As of March 31, 2019 and December 31, 2018, these asset classes consisted of short term foreign and US corporate bonds, equity securities, and commercial paper. Corporate bonds and commercial paper are classified within Level 2 of the fair value hierarchy because the fair value is based on observable market data. Equity securities are classified within Level 1 because fair value is based on quoted market prices in active markets for identical assets. The Company held equity securities with a fair value of $0.3 million at March 31, 2019, unchanged from December 31, 2018.

Other Investments

In the first quarter of 2019, the Company made a significant investment in an early stage venture and acquired a convertible debt instrument for $10 million. The Company elected to fair value the investment upon acquisition.

Other Fair Value Disclosures

The carrying amounts of cash and cash equivalents, accounts receivable, and accounts payable and accrued expenses approximate their fair values because of the relatively short-term maturities of these financial instruments. The fair value of the interest rate swap is measured using Level 2 inputs.

At March 31, 2019, the Company holds $33.1 million of equity and convertible debt securities consisting of non-controlling investments in privately held companies. These investments, over which the Company does not have the ability to exercise significant influence, are without readily determinable fair values. The investments are measured at cost, less any impairment, adjusted for observable price changes of similar investments of the same issuer. Fair value is not estimated for these investments if there are no identified events or changes in circumstances that may have an effect on the fair value of the investment. The carrying value of the strategic investments was $23.1 million at December 31, 2018. As of March 31, 2019 no impairments or price adjustments were recorded on the investments. These investments are included with other assets on the consolidated balance sheets.

The fair value of long-term debt is estimated using Level 2 inputs. At March 31, 2019, the fair value of long-term debt, including the current portion, was $90.6 million and its book value was $90.1 million. At December 31, 2018, the fair value of long-term debt, including the current portion, was $91.6 million and its book value was $91.0 million.