Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Recently Adopted Accounting Pronouncements [Abstract]
Reclassification adjustment related to gains on sale of securities	$ 0	$ 75,431
Cash Transactions [Abstract]
Interest paid	4,540,692	6,659,856
Income taxes paid, net	7,100,000	7,825,894
Noncash Transactions:
Loans charged-off to the allowance for loan losses	3,557,313	4,925,559	19,657,000
Loans foreclosed upon and transferred to other real estate owned	550,000	4,574,792
Available-for-sale securities transferred to held-to-maturity portfolio	39,959,647	0
Income Per Common Share [Abstract]
Number of incentive stocks outstanding (in shares)	219,000	612,000
Basic earnings per share calculation [Abstract]
Numerator - Net income available to common stockholders	13,448,125	7,205,788
Denominator - Average common shares outstanding (in shares)	33,987,265	33,811,871
Basic net income per share available to common stockholders (in dollars per share)	$ 0.40	$ 0.21
Diluted earnings per share calculation [Abstract]
Numerator - Net income available to common stockholders	$ 13,448,125	$ 7,205,788
Denominator - Average common shares outstanding (in shares)	33,987,265	33,811,871
Dilutive shares contingently issuable (in shares)	218,937	612,027
Average diluted common shares outstanding (in shares)	34,206,202	34,423,898
Diluted net income per share available to common stockholders (in dollars per share)	$ 0.39	$ 0.21