Valuation and Qualifying Accounts (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts
Balance at the beginning of year	$ 149,000	$ 134,000	$ 216,000
Additions charged to costs and expense	48,000	23,000	31,000
Deductions	(35,000)	(8,000)	(113,000)
Balance at end of year	162,000	149,000	134,000
Reserve for Inventory Valuation [Member]
Valuation and Qualifying Accounts
Balance at the beginning of year	693,000	753,000	916,000
Additions charged to costs and expense	58,000	45,000
Deductions	(343,000)	(105,000)	(163,000)
Balance at end of year	408,000	693,000	753,000
Deferred income tax valuation allowance [Member]
Valuation and Qualifying Accounts
Balance at the beginning of year	699,000	758,000	713,000
Additions charged to costs and expense	443,000		45,000
Deductions		(59,000)
Balance at end of year	$ 1,142,000	$ 699,000	$ 758,000