Notes Payable (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Notes Payable	$ 3,533,000	$ 3,933,000
Less current maturities	637,000	587,000
Notes payable - less current maturities	2,896,000	3,346,000
Limit on annual capital expenditures	1,500,000
Limit on annual capital expenditures, increase	3,500,000
Note payable to a Bank | Note payable due June 2021
Debt Instrument [Line Items]
Monthly payments	$ 26,000
Interest rate	3.99%
Note payable to a Bank	$ 1,071,000	1,329,000
Note payable to a Bank | Note Payable Due July 2031
Debt Instrument [Line Items]
Monthly payments	$ 11,000
Interest rate	5.29%
Note payable to a Bank	$ 1,234,000	1,293,000
Note payable to a Bank | Note payable due April 2021
Debt Instrument [Line Items]
Monthly payments	$ 6,200
Interest rate	5.29%
Note payable to a Bank	$ 227,000	288,000
Installment notes
Debt Instrument [Line Items]
Interest rate	4.20%
Installment notes, collateralized by certain machinery and equipment maturing at various dates, primarily through 2016, with interest at 1.0% through 6.7%.	$ 1,001,000	1,023,000
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Interest rate	4.49%
Notes Payable	$ 0	$ 0
Line of credit facility, maximum borrowing capacity	2,000,000
Summit Community Bank | Installment notes
Debt Instrument [Line Items]
Installment notes, collateralized by certain machinery and equipment maturing at various dates, primarily through 2016, with interest at 1.0% through 6.7%.	1,071,000
Minimum | Installment notes
Debt Instrument [Line Items]
Monthly payments	300
Maximum | Installment notes
Debt Instrument [Line Items]
Monthly payments	$ 4,100