Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Components of income tax expense
Current taxes - Federal	$ 240,000	$ (297,000)
Current taxes - State	10,000	6,000
Current taxes - Foreign	(13,000)	29,000
Deferred taxes - Federal	(167,000)	(107,000)
Deferred taxes - State	10,000	53,000
Deferred taxes - Foreign	(45,000)
Income tax expense (benefit)	35,000	(316,000)
Reconciliation of federal income taxes and reported income taxes
Statutory federal tax provision (benefit)	27,000	(302,000)
State income taxes	(32,000)	3,000
Effect of foreign operations	107,000	(5,000)
Uncertain tax positions	2,000	(3,000)
Income tax credits	(134,000)	(125,000)
Valuation allowance	49,000	86,000
Permanent differences	16,000	30,000
Income tax expense (benefit)	35,000	(316,000)
Income (loss) from operations before income taxes
Domestic	486,425	(968,793)
Foreign	(407,651)	81,371
Income (Loss) Before Income Taxes	78,774	(887,422)
Components of deferred tax assets (liabilities)
Allowance for uncollectable accounts	317,000	115,000
Inventories reserve	242,000	270,000
Accrued vacation	362,000	360,000
Non-compete amortization	56,000	191,000
Stock-based compensation and equity appreciation rights	29,000	111,000
Net operating loss carryforwards	134,000	113,000
Tax credit carryforwards	242,000	231,000
Other	188,000	180,000
Deferred tax assets before valuation allowance	1,570,000	1,571,000
Valuation allowance	(135,000)	(86,000)
Deferred tax assets	1,435,000	1,485,000
Prepaid expenses	(323,000)	(481,000)
Property and equipment	(569,000)	(663,000)
Deferred tax liabilities	(892,000)	(1,144,000)
Net deferred tax assets	543,000	341,000
Changes in total gross unrecognized tax benefit liabilities, excluding accrued interest
Balance at the beginning of the period	51,000	56,000
Additions based on tax positions related to the current year	15,000	12,000
Additions based on tax positions related to a prior year	5,000	2,000
Reductions based on tax positions related to a prior year	6,000	9,000
Statute of limitations	(13,000)	(10,000)
Balance at the end of the period	$ 52,000	$ 51,000