Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement Of Income And Comprehensive Income [Abstract]
Income tax (benefit) expense on unrealized holding (loss) income arising during the period	$ 2,288,044	$ (11,419,131)	$ 4,546,126	$ (13,144,225)
Income tax expense on reclassification adjustment for gains	$ 691,619	$ 426,354	$ 661,518	$ 882,146