Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 88,535,947	$ 86,485,242	$ 186,092,688	$ 166,765,236
Other comprehensive income (loss) before tax:
Foreign currency translation adjustments	1,495,210	(1,753,823)	1,683,800	(1,428,979)
Unrealized gains (losses) on derivatives	494,885	(120,474)	1,136,860	(1,472,031)
Unrealized gains on available-for sales securities, net	952,365	382,485	3,122,619	63,136
Other comprehensive income (loss), before tax	2,942,460	(1,491,812)	5,943,279	(2,837,874)
Expense (Benefit) for income taxes related to components of other comprehensive income (loss)	506,538	91,704	1,490,818	(493,112)
Other comprehensive income (loss), net of tax	2,435,922	(1,583,516)	4,452,461	(2,344,762)
Comprehensive Income	$ 90,971,869	$ 84,901,726	$ 190,545,149	$ 164,420,474