Summary Of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2016

Summary Of Significant Accounting Policies [Abstract]

Summary Of The Amortized Costs And Fair Values Of Marketable Securities

	(In thousands)
	MARKETABLE SECURITIES
	Amortized Cost		Fair Value		Gross Unrealized Gains		Gross Unrealized Losses
December 31, 2016
Tax-exempt Municipal Bonds	$	38,223	$	38,151	$	1	$	73
Variable Rate Demand Notes		46,306		46,306		-		-
Total Marketable Securities	$	84,529	$	84,457	$	1	$	73
December 31, 2015
Tax-exempt Municipal Bonds	$	20,129	$	20,115	$	4	$	18
Variable Rate Demand Notes		12,144		12,144		-		-
Total Marketable Securities	$	32,273	$	32,259	$	4	$	18

Schedule Of Estimated Future Amortization Expense

Years ending December 31:	(In thousands)
2017	$	3,024
2018		1,778
2019		21
2020		21
2021		21

Schedule Of Changes In Product Warranty

	(In thousands)
	Year Ended December 31
	2016		2015
Beginning balance January 1	$	487	$	377
Accruals during the period		549		677
Charges / payments made under the warranties		(493)		(567)
Balance December 31	$	543	$	487