Loans and the Allowance for Loan Losses (Details 6) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Loan portfolio by risk-rating grades
Total	$ 2,054,712	$ 1,530,101
Commercial, financial, agricultural [Member]
Loan portfolio by risk-rating grades
Total	360,062	231,697
Real estate - construction [Member]
Loan portfolio by risk-rating grades
Total	106,962	72,284
Real estate - 1-4 family mortgage [Member]
Loan portfolio by risk-rating grades
Total	172,322	152,874
Real estate - commercial mortgage [Member]
Loan portfolio by risk-rating grades
Total	1,415,362	1,073,239
Installment loans to individuals [Member]
Loan portfolio by risk-rating grades
Total	4	7
Pass [Member]
Loan portfolio by risk-rating grades
Total	1,913,561	1,383,422
Pass [Member] | Commercial, financial, agricultural [Member]
Loan portfolio by risk-rating grades
Total	330,739	226,540
Pass [Member] | Real estate - construction [Member]
Loan portfolio by risk-rating grades
Total	106,040	71,633
Pass [Member] | Real estate - 1-4 family mortgage [Member]
Loan portfolio by risk-rating grades
Total	129,710	96,147
Pass [Member] | Real estate - commercial mortgage [Member]
Loan portfolio by risk-rating grades
Total	1,347,068	989,095
Pass [Member] | Installment loans to individuals [Member]
Loan portfolio by risk-rating grades
Total	4	7
Watch [Member]
Loan portfolio by risk-rating grades
Total	74,254	72,876
Watch [Member] | Commercial, financial, agricultural [Member]
Loan portfolio by risk-rating grades
Total	27,455	1,939
Watch [Member] | Real estate - construction [Member]
Loan portfolio by risk-rating grades
Total	922	651
Watch [Member] | Real estate - 1-4 family mortgage [Member]
Loan portfolio by risk-rating grades
Total	13,960	24,138
Watch [Member] | Real estate - commercial mortgage [Member]
Loan portfolio by risk-rating grades
Total	31,917	46,148
Watch [Member] | Installment loans to individuals [Member]
Loan portfolio by risk-rating grades
Total	0	0
Substandard [Member]
Loan portfolio by risk-rating grades
Total	66,897	73,803
Substandard [Member] | Commercial, financial, agricultural [Member]
Loan portfolio by risk-rating grades
Total	1,868	3,218
Substandard [Member] | Real estate - construction [Member]
Loan portfolio by risk-rating grades
Total	0	0
Substandard [Member] | Real estate - 1-4 family mortgage [Member]
Loan portfolio by risk-rating grades
Total	28,652	32,589
Substandard [Member] | Real estate - commercial mortgage [Member]
Loan portfolio by risk-rating grades
Total	36,377	37,996
Substandard [Member] | Installment loans to individuals [Member]
Loan portfolio by risk-rating grades
Total	$ 0	$ 0