Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 104,280,411	$ 111,248,743
Other comprehensive income (loss) before tax:
Foreign currency translation adjustments	298,999	1,626,178
Unrealized gains on derivatives	0	67,047
Unrealized gains (losses) on debt securities, net	1,298,236	(21,280)
Other comprehensive income, before tax	1,597,235	1,671,945
Expense for income taxes related to components of other comprehensive income	272,631	9,611
Other comprehensive income, net of tax	1,324,604	1,662,334
Comprehensive Income	$ 105,605,015	$ 112,911,077