Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 111,897,852	$ 111,335,817	$ 325,136,888	$ 331,608,542
Other comprehensive (loss) income before tax:
Foreign currency translation adjustments	(1,623,102)	(1,174,213)	(1,799,789)	(2,013,638)
Unrealized gains on derivatives	0	16,165	0	98,769
Unrealized gains (losses) on debt securities, net	457,438	(609,422)	3,338,762	(932,953)
Other comprehensive (loss) income, before tax	(1,165,664)	(1,767,470)	1,538,973	(2,847,822)
Income tax impact related to components of other comprehensive income	96,062	(124,584)	701,140	(175,177)
Other comprehensive (loss) income, net of tax	(1,261,726)	(1,642,886)	837,833	(2,672,645)
Comprehensive Income	$ 110,636,126	$ 109,692,931	$ 325,974,721	$ 328,935,897