Statements of Comprehensive Income (Unaudited) - USD ($)	3 Months Ended						9 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Net income	$ 3,730,664	$ 3,822,062	$ 3,607,419	$ 3,421,405	$ 4,282,610	$ 3,945,049	$ 11,160,145	$ 11,649,064
Unrealized gain from marketable securities, net of tax	31,237	178,716	570,063	101,891	51,237	(107,027)	780,016	46,101
Comprehensive income	$ 3,761,901	$ 4,000,778	$ 4,177,482	$ 3,523,296	$ 4,333,847	$ 3,838,022	$ 11,940,161	$ 11,695,165