Earnings Per Share - Basic and Diluted Earnings Per Common Share (Details) - USD ($)	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share
Net income	$ 27,545,000	$ 28,904,000	$ 20,929,000
Weighted-average shares outstanding	9,189,876	9,193,235	8,734,334
Effect of dilutive securities stock options or awards	$ 9,293	$ 10,674	$ 11,188
Denominator for diluted earnings per share	$ 9,199,169	$ 9,203,909	$ 8,745,522
Basic earnings per share available to common stockholders	$ 3.00	$ 3.14	$ 2.40
Diluted earnings per share available to common stockholders	$ 2.99	$ 3.14	$ 2.39