Securities - Amortized Cost and Estimated Fair Value of Securities by Contractual Maturity (Detail) - USD ($)	Sep. 30, 2016	Dec. 31, 2015
Available-for-sale, Amortized Cost
Due in one year or less	$ 7,477,707	$ 3,008,448
Due after one year through five years	19,439,088	13,587,885
Due after five years through ten years	107,939,900	80,749,532
Due after ten years	318,859,282	169,962,891
Total Amortized Cost	453,715,977	267,308,756
Held-to-maturity, Amortized Cost
Due in one year or less	0	0
Due after five years through ten years		37,052,187
Due after ten years		123,991,217
Amortized Cost		161,043,404
Available-for-sale, Estimated Fair Value
Due in one year or less	7,546,148	3,028,887
Due after one year through five years	20,255,518	13,985,525
Due after five years through ten years	108,841,086	80,346,720
Due after ten years	320,008,565	169,903,271
Total Fair Value	456,651,317	267,264,403
Held-to-maturity, Estimated Fair Value
Due in one year or less	$ 0	0
Due after five years through ten years		38,528,059
Due after ten years		130,517,776
Total Fair Value		$ 169,045,835