Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 86,485,242	$ 74,558,437	$ 166,765,236	$ 151,741,878
Other comprehensive income (loss) before tax:
Foreign currency translation adjustments	(1,753,823)	300,766	(1,428,979)	(642,207)
Unrealized losses on derivatives	(120,474)	(36,229)	(1,472,031)	(1,867,920)
Unrealized gains (losses) on available-for sales securities, net	382,485	(2,986,559)	63,136	(3,564,244)
Other comprehensive loss, before tax	(1,491,812)	(2,722,022)	(2,837,874)	(6,074,371)
(Expense) Benefit for income taxes related to components of other comprehensive loss	91,704	(1,057,977)	(493,112)	(1,901,258)
Other comprehensive loss, net of tax	(1,583,516)	(1,664,045)	(2,344,762)	(4,173,113)
Comprehensive Income	$ 84,901,726	$ 72,894,392	$ 164,420,474	$ 147,568,765