Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 2,656,879	$ 1,942,810	$ 3,898,519	$ 6,897,203
Other comprehensive income (loss) components:
Foreign currency translation	3,121	(8,066)	(1,932)	(3,442)
Unrealized (loss) gain on short term investments	(71,242)	(8,919)	(80,223)	95,888
Reclassification adjustment for gains included in net income	(16,997)		(16,997)
Comprehensive income	$ 2,571,761	$ 1,925,825	$ 3,799,367	$ 6,989,649