(15) FAIR VALUE MEASUREMENTS

We account for certain assets and liabilities at fair value. The hierarchy below lists three levels of fair value based on the extent to which inputs used in measuring fair value are observable in the market. We categorize each of our fair value measurements in one of these three levels based on the lowest level input that is significant to the fair value measurement in its entirety. These levels are:

Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. We consider active markets as those in which transactions for the assets or liabilities occur in sufficient frequency and volume to provide pricing information on an ongoing basis. Our marketable securities are Level 1 instruments.

Level 2: Quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability. We have no Level 2 instruments.

Level 3: Measured based on prices or valuation models that require inputs that are both significant to the fair value measurement and less observable from objective sources (i.e., supported by little or no market activity). Our Level 3 instruments are comprised of interest rate swaps and impairment measurements. The fair values of our swaps were estimated using discounted cash flow calculations based upon forward interest-rate yield curves. Although we utilize third-party broker quotes to assess the reasonableness of our prices and valuation, we do not have sufficient corroborating market evidence to support classifying these assets and liabilities as Level 2. The Company also recorded impairments during Q4 of 2019 which incorporate Level 3 non-recurring fair value measures as further discussed in Note 2.

The following table summarizes our financial assets and liabilities measured on a recurring basis at fair value at December 31, 2019 and 2018 by respective level of the fair value hierarchy (in thousands):


	Level 1		Level 2		Level 3		Total
December 31, 2019
Assets:
Marketable securities - restricted (Note 4)	$	2,296	$	—	$	—	$	2,296
Liabilities:
Interest rate swaps	$	—	$	—	$	3,825	$	3,825
December 31, 2018
Assets:
Marketable securities	$	1,842	$	—	$	—	$	1,842
Marketable securities - restricted (Note 4)		1,909		—		—		1,909
	$	3,751	$	—	$	—	$	3,751
Liabilities:
Interest rate swaps	$	—	$	—	$	1,639	$	1,639

The table below highlights the change in fair value of the interest rate swaps which are based on a discounted future cash flow model (in thousands):


Ending balance, December 31, 2017	$	543
Change in estimated fair value		(2,182)
Ending balance, December 31, 2018		(1,639)
Change in estimated fair value		(2,186)
Ending balance, December 31, 2019*	$	(3,825)

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*Recorded in other liabilities in the Balance Sheet to these Consolidated Financial Statements.