SCHEDULE II - Valuation and Qualifying Accounts (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Allowance for Uncollectible Accounts
Changes in valuation and qualifying accounts
Balance at Beginning of Year	$ 320,000	$ 137,000
Additions Charged to Costs and Expenses	759,000	225,000
Deductions	(196,000)	(42,000)
Balance at End of Year	883,000	320,000
Inventory Reserves
Changes in valuation and qualifying accounts
Balance at Beginning of Year	750,000	732,000
Additions Charged to Costs and Expenses	595,000	457,000
Deductions	(672,000)	(439,000)
Balance at End of Year	$ 673,000	$ 750,000