Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 80,279,994	$ 77,183,441
Other comprehensive income (loss) before tax:
Foreign currency translation adjustments	324,844	(942,974)
Unrealized losses on derivatives	(1,351,557)	(1,831,690)
Unrealized losses on available-for sales securities, net	(319,349)	(577,685)
Other comprehensive loss, before tax	(1,346,062)	(3,352,349)
Benefit for income taxes related to components of other comprehensive loss	(584,816)	(843,281)
Other comprehensive loss, net of tax	(761,246)	(2,509,068)
Comprehensive Income	$ 79,518,748	$ 74,674,373