Condensed Consolidated Statements Of Comprehensive Income (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net income	$ 45,430,567	$ 46,344,584
Other comprehensive income (loss) before tax:
Foreign currency translation adjustments	(601,749)	344,785
Unrealized gains (losses) on available-for sales securities, net	9,194,861	13,514,130
Other comprehensive income (loss), before tax	8,593,112	13,858,915
Provision for income taxes related to components of other comprehensive income	3,218,201	4,729,945
Other comprehensive Income (loss), net of tax	5,374,911	9,128,970
Comprehensive Income	$ 50,805,478	$ 55,473,554