4. INVESTMENTS

The following table summarizes the Company’s investments at:

September 30, 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
Held-to-Maturity
Short-term:
Commercial paper	$	28,318	$	-	$	-	$	28,318	$	-	$	-
Municipal securities	181,843		-		222		181,621		222		-
U.S. government agency securities	26,080		1		3		26,078		3		-
Long-term:
Municipal securities	9,519		-		19		9,500		19		-

Available-for-Sale:
Short-term:
Variable rate demand notes	21,412		-		-		21,412		-		-
Total	$	267,172	$	1	$	244	$	266,929	$	244	$	-

December 31, 2015	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
Held-to-Maturity
Short-term:
Commercial paper	$	3,978	$	-	$	-	$	3,978	$	-	$	-
Municipal securities	709,207		63		192		709,078		192		-
U.S. government agency securities	23,369		-		58		23,311		58		-
U.S. Treasuries	8,056		-		13		8,043		13		-
Long-term:
Municipal securities	11,071		-		8		11,063		8		-
U.S. government agency securities	4,277		-		25		4,252		25		-
Total	$	759,958	$	63	$	296	$	759,725	$	296	$	-

During the three- and nine-months ended September 30, 2016 and 2015, realized gains or losses recognized on the sale of investments were not significant.

The Company’s investments at September 30, 2016 and December 31, 2015 in commercial paper, municipal securities, U.S. government agency securities, variable rate demand notes (“VRDNs”) and/or U.S. Treasuries 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, 2016				December 31, 2015
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Less than 1 year:
Commercial paper	$	28,318	$	28,318	$	3,978	$	3,978
Municipal securities	181,843		181,621		709,207		709,078
U.S. government agency securities	26,080		26,078		23,369		23,311
U.S. Treasuries	-		-		8,056		8,043
Due 1 -10 years:
Municipal securities	9,519		9,500		11,071		11,063
U.S. government agency securities	-		-		4,277		4,252
Variable rate demand notes	6,003		6,003		-		-
Due 11 - 20 years:
Variable rate demand notes	8,005		8,005		-		-
Due 21 - 30 years:
Variable rate demand notes	4,002		4,002		-		-
Due 31 - 40 years:
Variable rate demand notes	3,402		3,402		-		-
Total	$	267,172	$	266,929	$	759,958	$	759,725