Allowance for Loan Losses and Credit Quality Indicators (Details) - USD ($)	3 Months Ended								12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2019	Mar. 31, 2018
Allowance for Loan Losses [Roll Forward]
Balance at beginning of period				$ 66,088,139				$ 60,644,365	$ 66,088,139	$ 60,644,365	$ 60,923,204
Provision for loan losses	$ 28,533,000	$ 48,944,000	$ 40,359,000	30,591,000	$ 16,631,000	$ 40,456,000	$ 32,824,000	27,710,000	148,426,578	117,620,140	119,095,712
Loan losses									(148,308,199)	(127,387,857)	(135,100,416)
Recoveries									15,313,106	15,211,491	15,725,865
Balance at end of period	81,519,624				66,088,139				81,519,624	66,088,139	60,644,365
Summary of loans individually and collectively evaluated for impairment [Abstract]
Bankruptcy, gross loans												$ 4,644,203	$ 4,627,599
91 days or more delinquent, excluding bankruptcy												59,633,541	50,019,567
Loans less than 91 days delinquent and not in bankruptcy												1,063,679,639	949,585,993
Unearned interest and fees													(258,991,492)
Net loans												837,143,631	745,241,667
Allowance for loan losses	(81,519,624)			(66,088,139)	(66,088,139)			$ (60,644,365)	(66,088,139)	(60,644,365)	$ (60,923,204)	(81,519,624)	(66,088,139)
Loans receivable, net												755,624,007	679,153,528
Loans individually evaluated for impairment (impaired loans) [Member]
Allowance for Loan Losses [Roll Forward]
Balance at beginning of period				38,782,574					38,782,574
Balance at end of period	45,511,124				38,782,574				45,511,124	38,782,574
Summary of loans individually and collectively evaluated for impairment [Abstract]
Bankruptcy, gross loans												4,644,203	4,627,599
91 days or more delinquent, excluding bankruptcy												59,633,541	50,019,567
Loans less than 91 days delinquent and not in bankruptcy												0	0
Unearned interest and fees												(14,319,795)	(11,433,666)
Net loans												49,957,949	43,213,500
Allowance for loan losses	(45,511,124)			(38,782,574)	(38,782,574)				(38,782,574)	(38,782,574)		(45,511,124)	(38,782,574)
Loans receivable, net												4,446,825	4,430,926
Loans collectively evaluated for impairment [Member]
Allowance for Loan Losses [Roll Forward]
Balance at beginning of period				27,305,565					27,305,565
Balance at end of period	36,008,500				27,305,565				36,008,500	27,305,565
Summary of loans individually and collectively evaluated for impairment [Abstract]
Bankruptcy, gross loans												0	0
91 days or more delinquent, excluding bankruptcy												0	0
Loans less than 91 days delinquent and not in bankruptcy												1,063,679,639	949,585,993
Unearned interest and fees												(276,493,957)	(247,557,826)
Net loans												787,185,682	702,028,167
Allowance for loan losses	$ (36,008,500)			$ (27,305,565)	$ (27,305,565)				$ (27,305,565)	$ (27,305,565)		(36,008,500)	(27,305,565)
Loans receivable, net												$ 751,177,182	$ 674,722,602