CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income:	$ 173,979,487	$ 127,224,695	$ 95,509,402
Other comprehensive income (loss), net of tax:
Total other comprehensive income (loss), net of tax	9,990,675	(10,741,276)	(7,643,590)
Changes in fair value of cash flow hedges, net of tax	2,139,703	(800,188)	(1,725,136)
Changes in fair value on available-for-sale securities, net of tax	2,828,551	(9,700,933)	(5,582,965)
Net loss (gain) on sale of investment securities reclassified from other comprehensive income into net income, net of tax	5,022,421	(240,155)	(335,489)
Total comprehensive income	$ 183,970,162	$ 116,483,419	$ 87,865,812