Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 3,844,290	$ 2,581,142
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	200,677	187,035
Realized (gain) loss on sales of marketable securities	(33,297)	1,011
Bad debt expense	4,277	8,289
Deferred income taxes	(31,760)	59,712
(Decrease) increase in cash resulting from changes in operating assets and liabilities:
Accounts receivable	(311,695)	(671,532)
Inventories	(84,710)	37,829
Prepaid expenses and other current and non-current assets	(37,644)	25,213
Prepaid income taxes	82,401	13,035
Accounts payable	271,464	(13,995)
Income taxes payable	55,848
Accrued expenses	32,999	62,705
Dividends payable	(563)
Net cash provided by operating activities	3,992,287	2,290,444
Cash flows from investing activities:
Acquisitions of property, plant and equipment	(38,149)	(166,689)
Purchases of marketable securities	(1,922,513)	(2,309,935)
Proceeds from sales of marketable securities	4,776,044	2,966,859
Net cash provided by investing activities	2,815,382	490,235
Cash flows from financing activities:
Dividends paid	(6,507,249)	(3,436,867)
Net cash used in financing activities	(6,507,249)	(3,436,867)
Net increase(decrease) in cash and cash equivalents	300,420	(656,188)
Cash and cash equivalents, beginning of year	424,301	1,080,489
Cash and cash equivalents, end of year	$ 724,721	$ 424,301