Investments consist of the following as of September 30, 2021 and December 31, 2020 (dollars in thousands):

	September 30, 2021
			Gross Unrealized
	Cost		Gain		(Loss)			Fair Value
Short-term investments (available for sale):
Municipal bonds	$	5,057	$	-	$	(3	)	$	5,054
Non-governmental debt securities		203,643		38		(65	)		203,616
Treasury and federal agencies		723		1		(3	)		721
Total short-term investments (available for sale)	$	209,423	$	39	$	(71	)	$	209,391

	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 for which little or no market data exists, therefore requiring an entity to develop its own assumptions.

As of September 30, 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 September 30, 2021 and December 31, 2020. Additionally, money market funds of $190.1 million and $1.7 million included within cash and cash equivalents on our condensed consolidated balance sheets as of September 30, 2021 and December 31, 2020, respectively, were measured under Level 1 and certificates of deposit, commercial paper and treasury bills of $5.1 million included within cash and cash equivalents on our condensed consolidated balance sheets as of December 31, 2020 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 September 30, 2021, our investment in an equity affiliate equated to a 30.7%, or $3.1 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 September 30, 2021 and 2020, we recorded less than $0.1 million of loss and approximately $0.1 million of gain, respectively, and during the years to date ended September 30, 2021 and 2020, we recorded approximately $0.1 million of gain and $0.2 million of gain, respectively, related to our proportionate investment in CCKF within miscellaneous (expense) income on our unaudited condensed consolidated statements of income.

We make periodic operating maintenance payments to CCKF 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 September 30, 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 and $1.2 million was recognized as expense for the quarter and year to date ended September 30, 2020, respectively.

On September 8, 2021, the Company and the subsidiary guarantors thereunder entered into a credit agreement with Wintrust Bank N.A. (“Wintrust”), in its capacities as the sole lead arranger, sole bookrunner, administrative agent and letter of credit issuer for the lenders from time to time parties thereto. The credit agreement provides the Company with the benefit of a $125.0 million senior secured revolving credit facility. The $125.0 million revolving credit facility under the credit agreement is scheduled to mature on September 8, 2024. So long as no default has occurred and other conditions have been met, the Company may request an increase in the aggregate commitment in an amount not to exceed $50.0 million. The loans and letter of credit obligations under the credit agreement are secured by substantially all assets of the Company and the subsidiary guarantors.

The credit agreement and the ancillary documents executed in connection therewith contain customary affirmative, negative and financial maintenance covenants. The Company is required to maintain unrestricted cash, cash equivalents and short-term investments in domestic accounts in an amount at least equal to the aggregate loan commitments then in effect. Acquisitions to be undertaken by the Company must meet certain criteria, and the Company’s ability to make restricted payments, including payments in connection with a repurchase of shares of our common stock, is subject to an aggregate maximum of $100.0 million per fiscal year. Upon the occurrence of certain regulatory events or if the Company’s unrestricted cash, cash equivalents and short term investments are less than 125% of the aggregate amount of the loan commitments then in effect, the Company is required to maintain cash in a segregated, restricted account in an amount not less than the aggregate loan commitments then in effect. The credit agreement also contains customary representations and warranties, events of default, and rights and remedies upon the occurrence of any event of default thereunder, including rights to accelerate the loans, terminate the commitments and realize upon the collateral securing the obligations under the credit agreement.

Under the credit agreement, outstanding principal amounts bear annual interest at a fluctuating rate equal to 1.0% less than the administrative agent’s prime commercial rate, subject to a 3.0% minimum rate. A higher rate may apply to late payments or if any event of default exists.

This credit agreement with Wintrust replaced the previous $50.0 million revolving credit facility set forth in the credit agreement dated as of December 27, 2018 with BMO Harris Bank N.A. As of September 30, 2021 and December 31, 2020, there were no outstanding borrowings under the current or prior revolving credit facility.