Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Held to maturity, fair value	$ 380,450,428	$ 344,647,138
Available for sale, amortized cost	538,414,337	511,629,644
Equity securities, available for sale, at cost	$ 44,219,097	$ 42,431,695
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued	0	0
Class A Common Stock [Member]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	25,564,481	24,483,377
Common stock, shares outstanding	22,561,893	21,480,789
Class B Common Stock [Member]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	10,000,000	10,000,000
Common stock, shares issued	5,649,240	5,649,240
Common stock, shares outstanding	5,576,775	5,576,775