Statements of Comprehensive Income - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Net income	$ 3,844,290	$ 2,581,142
Other comprehensive income:
Unrealized gain on marketable securities	323,793	156,474
Income tax expense related to other comprehensive income	(67,997)	(53,201)
Total other comprehensive income, net of tax	255,796	103,273
Total comprehensive income	$ 4,100,086	$ 2,684,415