SCHEDULE II - Valuation and Qualifying Accounts (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2011
Allowance for Uncollectible Accounts
Changes in valuation and qualifying accounts
Balance at Beginning of Year	$ 138,000		$ 157,000
Additions Charged to Costs and Expenses	52,000	41,000
Deductions	(53,000)	(60,000)
Balance at End of Year	137,000	138,000	157,000
Inventory Reserves
Changes in valuation and qualifying accounts
Balance at Beginning of Year	1,100,000		1,474,000
Additions Charged to Costs and Expenses	524,000	718,000
Deductions	(892,000)	(1,092,000)
Balance at End of Year	$ 732,000	$ 1,100,000	$ 1,474,000