Investments consist of the following as of March 31, 2021 and December 31, 2020 (dollars in thousands):

	March 31, 2021
			Gross Unrealized
	Cost		Gain		(Loss)			Fair Value
Short-term investments (available for sale):
Municipal bonds	$	139	$	1	$	-		$	140
Non-governmental debt securities		354,136		145		(208	)		354,073
Treasury and federal agencies		6,770		5		(2	)		6,773
Total short-term investments (available for sale)	$	361,045	$	151	$	(210	)	$	360,986

	December 31, 2020
			Gross Unrealized
	Cost		Gain		(Loss)			Fair Value
Short-term investments (available for sale):
Municipal bonds	$	139	$	1	$	-		$	140
Non-governmental debt securities		288,578		331		(176	)		288,733
Treasury and federal agencies		11,799		6		(2	)		11,803
Total short-term investments (available for sale)	$	300,516	$	338	$	(178	)	$	300,676

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 March 31, 2021, 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 March 31, 2021 and December 31, 2020. Additionally, money market funds of $20.9 million and $1.7 million included within cash and cash equivalents on our condensed consolidated balance sheets as of March 31, 2021 and December 31, 2020, respectively, were measured under Level 1 and certificates of deposit, commercial paper and treasury bills of $5.5 million and $5.1 million included within cash and cash equivalents on our condensed consolidated balance sheets as of March 31, 2021 and December 31, 2020, respectively, were measured under Level 2.

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 March 31, 2021, our investment in an equity affiliate equated to a 30.7%, or $3.2 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 the quarters ended March 31, 2021 and 2020, we recorded approximately $0.2 million of gain and $0.1 million of gain, respectively, related to our proportionate investment in CCKF within miscellaneous income (expense) on our unaudited condensed consolidated statements of income.

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 ended March 31, 2021 and 2020 were as follows (dollars in thousands):

(1)During the first quarter of 2020, the Company prepaid maintenance payments for the full year 2020, of which approximately $0.4 million was recognized as expense for the quarter ended March 31, 2020.

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. (“BMO Harris”), 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 March 31, 2021 and December 31, 2020, there were no outstanding borrowings under the revolving credit facility.