Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Summary of Investments

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

	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

	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

Schedule of Available-for-Sale Investments

A schedule of available-for-sale investments segregated by their original stated terms to maturity as of December 31, 2020 and 2019 are as follows (dollars in thousands): 

	Less than one year		One to five years		Six to ten years		Greater than ten years		Total
Original stated term to maturity of available-for-sale-    investments as of December 31, 2020	$	182,959	$	117,641	$	-	$	76	$	300,676
Original stated term to maturity of available-for-sale-    investments as of December 31, 2019	$	125,087	$	59,751	$	-	$	650	$	185,488

Schedule of Maintenance Fee Payment to CCKF

We make periodic operating maintenance payments related to proprietary rights that we use in our intellipath^® personalized learning technology. The total fees recorded for the years ended December 31, 2020, 2019 and 2018 were as follows (dollars in thousands):

	Maintenance Fee Payments
For the year ended December 31, 2020	$	1,596
For the year ended December 31, 2019	$	1,418
For the year ended December 31, 2018	$	1,462