Fair Values of Financial Instruments (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
Assets [Abstract]
Trading securities	$ 213,000		$ 203,000
Securities available for sale	571,762,000		533,178,000
Liabilities [Abstract]
Subordinated debentures	35,569,000		35,569,000
Reciprocal deposits included in deposits with no stated maturity	17,200,000		13,600,000
Reciprocal deposits included in deposits with stated maturity	41,500,000		40,100,000
Recorded Book Balance [Member]
Assets [Abstract]
Cash and due from banks	46,435,000		48,326,000
Interest bearing deposits	55,117,000		25,690,000
Interest bearing deposits - time	11,575,000		13,561,000
Trading securities	213,000		203,000
Securities available for sale	571,762,000		533,178,000
Federal Home Loan Bank and Federal Reserve Bank Stock	20,051,000		19,919,000
Net loans and loans held for sale	1,429,212,000		1,407,634,000
Accrued interest receivable	6,250,000		5,995,000
Derivative financial instruments	1,268,000		619,000
Liabilities [Abstract]
Deposits with no stated maturity	1,626,558,000	[1]	1,534,175,000	[1]
Deposits with stated maturity	373,915,000	[1]	390,127,000	[1]
Other borrowings	12,468,000		12,470,000
Subordinated debentures	35,569,000		35,569,000
Accrued interest payable	364,000		380,000
Derivative financial instruments	666,000		366,000
Fair Value [Member]
Assets [Abstract]
Cash and due from banks	46,435,000		48,326,000
Interest bearing deposits	55,117,000		25,690,000
Interest bearing deposits - time	11,575,000		13,585,000
Trading securities	213,000		203,000
Securities available for sale	571,762,000		533,178,000
Net loans and loans held for sale	1,416,980,000		1,394,424,000
Accrued interest receivable	6,250,000		5,995,000
Derivative financial instruments	1,268,000		619,000
Liabilities [Abstract]
Deposits with no stated maturity	1,626,558,000	[1]	1,534,175,000	[1]
Deposits with stated maturity	373,144,000	[1]	389,139,000	[1]
Other borrowings	14,508,000		14,560,000
Subordinated debentures	21,974,000		23,328,000
Accrued interest payable	364,000		380,000
Derivative financial instruments	666,000		366,000
Quoted Prices in Active Markets for Identical Assets, (Level 1) [Member]
Assets [Abstract]
Cash and due from banks	46,435,000		48,326,000
Interest bearing deposits	55,117,000		25,690,000
Interest bearing deposits - time	0		0
Trading securities	213,000		203,000
Securities available for sale	0		0
Net loans and loans held for sale	0		0
Accrued interest receivable	5,000		2,000
Derivative financial instruments	0		0
Liabilities [Abstract]
Deposits with no stated maturity	1,626,558,000	[1]	1,534,175,000	[1]
Deposits with stated maturity	0	[1]	0	[1]
Other borrowings	0		0
Subordinated debentures	0		0
Accrued interest payable	20,000		21,000
Derivative financial instruments	0		0
Significant Other Observable Inputs, (Level 2) [Member]
Assets [Abstract]
Cash and due from banks	0		0
Interest bearing deposits	0		0
Interest bearing deposits - time	11,575,000		13,585,000
Trading securities	0		0
Securities available for sale	571,762,000		533,178,000
Net loans and loans held for sale	30,932,000		23,662,000
Accrued interest receivable	1,808,000		1,599,000
Derivative financial instruments	1,268,000		619,000
Liabilities [Abstract]
Deposits with no stated maturity	0	[1]	0	[1]
Deposits with stated maturity	373,144,000	[1]	389,139,000	[1]
Other borrowings	14,508,000		14,560,000
Subordinated debentures	21,974,000		23,328,000
Accrued interest payable	344,000		359,000
Derivative financial instruments	666,000		366,000
Significant Unobservable Inputs, (Level 3) [Member]
Assets [Abstract]
Cash and due from banks	0		0
Interest bearing deposits	0		0
Interest bearing deposits - time	0		0
Trading securities	0		0
Securities available for sale	0		0
Net loans and loans held for sale	1,386,048,000		1,370,762,000
Accrued interest receivable	4,437,000		4,394,000
Derivative financial instruments	0		0
Liabilities [Abstract]
Deposits with no stated maturity	0	[1]	0	[1]
Deposits with stated maturity	0	[1]	0	[1]
Other borrowings	0		0
Subordinated debentures	0		0
Accrued interest payable	0		0
Derivative financial instruments	$ 0		$ 0

[1] Deposits with no stated maturity include reciprocal deposits with a recorded book balance of $17.2 million and $13.6 million at March 31, 2015 and December 31, 2014, respectively. Deposits with a stated maturity include reciprocal deposits with a recorded book balance of $41.5 million and $40.1 million at March 31, 2015 and December 31, 2014, respectively.