Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Recently Adopted Accounting Pronouncements [Abstract]
Net gain on sale of investment securities reclassified out of comprehensive income into net income, net of tax	$ 875,838		$ 30,254	$ 891,177	$ (98,893)
Cash Transactions [Abstract]
Interest paid				12,434,753	18,317,526
Income taxes paid, net				20,850,009	5,699,106
Noncash Transactions:
Loans charged-off to the allowance for loan losses				14,088,656	11,265,378	19,657,000
Loans foreclosed upon and transferred to other real estate owned				3,491,421	8,489,792
Available-for-sale securities transferred to held-to-maturity portfolio		39,959,647		39,959,647	0
Income Per Common Share [Abstract]
Number of incentive stocks outstanding (in shares)	323,668		583,828	267,214	594,709
Basic earnings per share calculation [Abstract]
Numerator - Net income available to common stockholders	14,646,950		11,349,125	42,405,607	26,339,683
Denominator - Average common shares outstanding (in shares)	34,282,899		33,939,248	34,148,562	33,879,186
Basic net income per share available to common stockholders (in dollars per share)	$ 0.43		$ 0.33	$ 1.24	$ 0.78
Diluted earnings per share calculation [Abstract]
Numerator - Net income available to common stockholders	$ 14,646,950		$ 11,349,125	$ 42,405,607	$ 26,339,683
Denominator - Average common shares outstanding (in shares)	34,282,899		33,939,248	34,148,562	33,879,186
Dilutive shares contingently issuable (in shares)	323,668		583,828	267,214	594,709
Average diluted common shares outstanding (in shares)	34,606,567		34,523,076	34,415,776	34,473,895
Diluted net income per share available to common stockholders (in dollars per share)	$ 0.42		$ 0.33	$ 1.23	$ 0.76