3.INVESTMENTS

The following table summarizes the Company’s investments at:

September 30, 2017	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value		Continuous Unrealized Loss Position less than 12 Months		Continuous Unrealized Loss Position greater than 12 Months
Available-for-sale
Short-term:
Commercial paper	$	66,344	$	-	$	-	$	66,344	$	-	$	-
Certificates of deposit	50,677		-		-		50,677		-		-
Municipal securities	402,062		41		126		401,977		126		-
U.S. government agency securities	53,342		1		28		53,315		28		-
U.S. Treasuries	11,982		-		1		11,981		1		-
Variable rate demand notes	46,054		-		-		46,054		-		-
Long-term:
Municipal securities	2,010		-		3		2,007		3		-
U.S. government agency securities	5,001		-		5		4,996		5		-

Total	$	637,472	$	42	$	163	$	637,351	$	163	$	-


December 31, 2016	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value		Continuous Unrealized Loss Position less than 12 Months		Continuous Unrealized Loss Position greater than 12 Months

Available-for-sale
Short-term:
Commercial paper	$	40,382	$	-	$	-	$	40,382	$	-	$	-
Municipal securities	140,379		-		181		140,198		181		-
U.S. government agency securities	26,057		-		6		26,051		6		-
Variable rate demand notes	13,923		-		-		13,923		-		-
Long-term:
Municipal securities	2,403		-		9		2,394		9		-

Total	$	223,144	$	-	$	196	$	222,948	$	196	$	-

During the three- and nine-months ended September 30, 2017 and 2016, realized gains or losses recognized on the sale of investments were not significant.

The Company’s investments at September 30, 2017 and December 31, 2016 in commercial paper, certificates of deposit, municipal securities, U.S. Treasuries, U.S. government agency securities and/or variable rate demand notes (“VRDNs”) carried investment grade credit ratings. VRDNs are floating rate municipal bonds with embedded put options that allow the bondholder to sell the security at par plus accrued interest. All of the put options are secured by a pledged liquidity source. While they are classified as marketable investment securities, the put option allows the VRDNs to be liquidated at par on a same day, or more generally, on a seven-day settlement basis.

The following table summarizes the underlying contractual maturities of the Company’s investments at:

	September 30, 2017				December 31, 2016

	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Less than 1 year:
Commercial paper	$	66,344	$	66,344	$	40,382	$	40,382
Certificates of deposit	50,677		50,677		-		-
Municipal securities	402,062		401,977		140,379		140,198
U. S. Treasuries	11,982		11,981		-		-
U.S. government agency securities	53,342		53,315		26,057		26,051
Due 1 -10 years:
Municipal securities	2,010		2,007		2,403		2,394
U.S. government agency securities	5,001		4,996		-		-
Variable rate demand notes	6,664		6,664		3,917		3,917
Due 11 - 20 years:
Variable rate demand notes	26,016		26,016		6,003		6,003
Due 21 - 30 years:
Variable rate demand notes	13,374		13,374		4,003		4,003

Total	$	637,472	$	637,351	$	223,144	$	222,948