4.INVESTMENTS

The following table summarizes the Company’s investments at:

March 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
Held-to-Maturity
Short-term:
Commercial paper	$	7,969	$	-	$	-	$	7,969	$	-	$	-
Municipal securities	464,865		22		148		464,739		148		-
U.S. government agency securities	17,316		1		7		17,310		7		-
U.S. Treasuries	18,093		1		-		18,094		-		-
Long-term:
Municipal securities	7,419		-		8		7,411		8		-

Total	$	515,662	$	24	$	163	$	515,523	$	163	$	-


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-months ended March 31, 2016 and 2015, realized gains or losses recognized on the sale of investments were not significant.

The Company’s investments at March 31, 2016 and December 31, 2015 in commercial paper, U.S. Treasuries, municipal securities and U.S. government agency securities carried investment grade credit ratings.

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

	March 31, 2016				December 31, 2015
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Less than 1 year:
Commercial paper	$	7,969	$	7,969	$	3,978	$	3,978
Municipal securities	464,865		464,739		709,207		709,078
U.S. government agency securities	17,316		17,310		23,369		23,311
U.S. Treasuries	18,093		18,094		8,056		8,043
Due 1 -10 years:
Municipal securities	5,334		5,328		11,071		11,063
U.S. government agency securities	-		-		4,277		4,252
Due 11 - 20 years:
Municipal securities	2,085		2,083		-		-

Total	$	515,662	$	515,523	$	759,958	$	759,725