Annual report pursuant to Section 13 and 15(d)

Schedule II Valuation and Qualifying Accounts (Details)

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Schedule II Valuation and Qualifying Accounts (Details) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Allowance for Doubtful Accounts [Member]      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period $ 82,000 $ 247,000 $ 1,115,000
Charged to (Reduction of) Cost and Expenses 202,000 (45,000) 104,000
Deductions (249,000) (120,000) (972,000)
Balance at End of Period 35,000 82,000 247,000
Allowance for Doubtful Accounts [Member] | Notes Receivable [Member] | Palmer of Texas [Member]      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Charged to (Reduction of) Cost and Expenses     801,000
Increase (Decrease) in Accounts Receivable     299,000
Inventory Valuation Reserve [Member]      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period 966,000 682,000 725,000
Charged to (Reduction of) Cost and Expenses 1,237,000 984,000 767,000
Deductions (1,506,000) (700,000) (810,000)
Balance at End of Period $ 697,000 $ 966,000 $ 682,000