Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 111,335,817	$ 90,230,335	$ 331,608,542	$ 276,323,023
Other comprehensive income (loss) before tax:
Foreign currency translation adjustments	(1,174,213)	1,182,152	(2,013,638)	2,865,952
Unrealized gains on derivatives	16,165	239,215	98,769	1,376,077
Unrealized (losses) gains on debt securities, net	(609,422)	2,287,103	(932,953)	5,409,722
Other comprehensive (loss) income, before tax	(1,767,470)	3,708,470	(2,847,822)	9,651,751
(Benefit) Expense for income taxes related to components of other comprehensive income (loss)	(124,584)	884,211	(175,177)	2,375,031
Other comprehensive (loss) income, net of tax	(1,642,886)	2,824,259	(2,672,645)	7,276,720
Comprehensive Income	$ 109,692,931	$ 93,054,594	$ 328,935,897	$ 283,599,743