Investments consist of the following as of June 30, 2020 and December 31, 2019 (dollars in thousands):

	June 30, 2020
			Gross Unrealized
	Cost		Gain		(Loss)			Fair Value
Short-term investments (available for sale):
Municipal bonds	$	1,538	$	2	$	-		$	1,540
Non-governmental debt securities		219,215		975		(37	)		220,153
Treasury and federal agencies		28,525		49		(2	)		28,572
Total short-term investments (available for sale)	$	249,278	$	1,026	$	(39	)	$	250,265

	December 31, 2019
			Gross Unrealized
	Cost		Gain		(Loss)			Fair Value
Short-term investments (available for sale):
Municipal bonds	$	1,361	$	3	$	-		$	1,364
Non-governmental debt securities		165,423		433		(37	)		165,819
Treasury and federal agencies		18,307		7		(9	)		18,305
Total short-term investments (available for sale)	$	185,091	$	443	$	(46	)	$	185,488

In the table above, unrealized holding gains (losses) relate to short-term investments that have been in a continuous unrealized gain (loss) position for less than one year.

Our non-governmental debt securities primarily consist of commercial paper and certificates of deposit. Our treasury and federal agencies primarily consist of U.S. Treasury bills and federal home loan debt securities. We do not intend to sell our investments in these securities prior to maturity and it is not likely that we will be required to sell these investments before recovery of the amortized cost basis.

FASB ASC Topic 820 – Fair Value Measurements establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions.

As of June 30, 2020, we held investments that are required to be measured at fair value on a recurring basis. These investments (available for sale) consist of municipal bonds, non-governmental debt securities and treasury and federal agencies securities. Available for sale securities included in Level 2 are estimated based on observable inputs other than quoted prices in active markets for identical assets and liabilities, such as quoted prices for identical or similar assets or liabilities in inactive markets or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

All of our available for sale investments were measured under Level 2 as of June 30, 2020 and December 31, 2019.

Our investment in an equity affiliate, which is recorded within other noncurrent assets on our condensed consolidated balance sheets, represents an international investment in a private company. As of June 30, 2020, our investment in an equity affiliate equated to a 30.7%, or $2.8 million, non-controlling interest in CCKF, a Dublin-based educational technology company providing intelligent systems to power the delivery of individualized and personalized learning.

During each of the quarters and years to date ended June 30, 2020 and 2019, we recorded approximately $0.1 million of gain for each respective period, related to our proportionate investment in CCKF within miscellaneous income on our unaudited condensed consolidated statements of income (loss).

We make periodic operating maintenance payments related to proprietary rights that we use in our intellipath^® personalized learning technology. The total fees paid during the quarters and years to date ended June 30, 2020 and 2019 were as follows (dollars in thousands):

(1)During the first quarter of 2020, the Company prepaid approximately $1.4 million of maintenance payments, of which approximately $0.4 million and $0.8 million was recognized as expense for the quarter and year to date ended June 30, 2020, respectively.

On December 27, 2018, the Company; its wholly-owned subsidiary, CEC Educational Services, LLC; and the subsidiary guarantors thereunder, entered into a credit agreement with BMO Harris Bank N.A., in its capacities as the sole lender, the letter of credit issuer thereunder and the administrative agent for the lenders which from time to time may be parties to the credit agreement. The credit agreement provides the Company with the benefit of a $50.0 million revolving credit facility and is scheduled to mature on January 20, 2022. The loans and letter of credit obligations under the credit agreement are required to be 100% secured with cash and marketable securities deposited with the bank. As of June 30, 2020 and December 31, 2019, there were no outstanding borrowings under the revolving credit facility.