Credit Quality of Loans and Allowance for Loan Losses - Troubled Debt Restructurings (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) contract	Sep. 30, 2015 USD ($) contract	Sep. 30, 2016 USD ($) contract	Sep. 30, 2015 USD ($) contract	Dec. 31, 2015 USD ($)
Financing Receivable, Modifications [Line Items]
Current	$ 13,000		$ 13,000		$ 16,000
Past Due Greater Than 30 Days	140,000		140,000		148,000
Nonaccrual TDRs	26,141,000		26,141,000		20,865,000
Total TDRs	$ 26,294,000		$ 26,294,000		21,029,000
Pre-modified contracts identified as TDRs (contracts) | contract	0	0	1	1
Number of TDR defaulted (contracts) | contract	0	1	1	1
TDRs defaulted, amount		$ 21,100,000	$ 5,500,000	$ 21,100,000
Pre-modification balance identified as TDR			5,500,000	$ 21,400,000
Commitments to lend additional funds	$ 0		0
Commercial, financial and agricultural
Financing Receivable, Modifications [Line Items]
Current	13,000		13,000		16,000
Past Due Greater Than 30 Days	0		0		0
Nonaccrual TDRs	24,568,000		24,568,000		20,865,000
Total TDRs	24,581,000		24,581,000		20,881,000
Real estate – commercial
Financing Receivable, Modifications [Line Items]
Current	0		0		0
Past Due Greater Than 30 Days	140,000		140,000		148,000
Nonaccrual TDRs	1,573,000		1,573,000		0
Total TDRs	$ 1,713,000		$ 1,713,000		$ 148,000