Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Dec. 31, 2011
Available-for-sale Securities, Balance Sheet, Reported Amounts [Abstract]
Amortized cost	$ 316,617	$ 316,617	$ 291,103
Unrealized gains	6,884	6,884	5,737
Unrealized losses	(824)	(824)	(885)
Fair value	322,677	322,677	295,955
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	24,885	24,885	51,879
12 months or more, fair value	6,528	6,528	2,006
Total fair value	31,413	31,413	53,885
Less than 12 months, unrealized losses	(334)	(334)	(873)
12 months or more, unrealized losses	(490)	(490)	(12)
Unrealized losses	(824)	(824)	(885)
Number of securities temporarily impaired	17	17	10
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Three months or less, fair value	5,503	5,503
Over three months to one year or less, fair value	22,624	22,624
After one year through three years, fair value	24,234	24,234
After three years through five years, fair value	219,243	219,243
After five years through ten years, fair value	17,802	17,802
After ten years, fair value	33,271	33,271
Total cost - fair value	322,677	322,677
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Three months or less, amortized cost	5,499	5,499
Over three months to one year, amortized cost	22,464	22,464
After one year through three years, fair value	23,784	23,784
After year three through five years, amortized cost	216,223	216,223
After five through ten years, amortized cost	17,129	17,129
After ten years, amortized cost	31,518	31,518
Total amortized cost	316,617	316,617
Pledged Financial Instruments, Not Separately Reported, Securities [Abstract]
To state and local governments to secure public deposits, amortized cost	68,403	68,403
To Federal Reserve Bank to secure borrowings, amortized cost	22,493	22,493
To Federal Home Loan Bank to secure borrowings, amortized cost	1,131	1,131
Other securities pledged, principally to secure deposits, amortized cost	15,888	15,888
Total pledged investment securities, amortized cost	107,915	107,915
Pledged Assets Separately Reported, Securities Pledged as Collateral, at Fair Value, by Type of Agreement [Abstract]
To state and local governments to secure public deposits, fair value	70,930	70,930
To Federal Reserve Bank to secure borrowings, fair value	23,100	23,100
To Federal Home Loan Bank to secure borrowings, fair value	1,157	1,157
Other securities pledged, principally to secure deposits, fair value	16,475	16,475
Total pledged investment securities, fair value	111,662	111,662
Realized gains from the sale of securities available for sale	344	344
Realized losses from the sale of securities available for sale	2	2
US Government Agencies [Member]
Available-for-sale Securities, Balance Sheet, Reported Amounts [Abstract]
Amortized cost	80,138	80,138	75,383
Unrealized gains	1,338	1,338	1,207
Unrealized losses	(8)	(8)	(16)
Fair value	81,468	81,468	76,574
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	2,056	2,056	10,499
12 months or more, fair value			0
Total fair value	2,056	2,056	10,499
Less than 12 months, unrealized losses	(8)	(8)	(16)
12 months or more, unrealized losses	0	0	0
Unrealized losses	(8)	(8)	(16)
US Treasury [Member]
Available-for-sale Securities, Balance Sheet, Reported Amounts [Abstract]
Amortized cost	14,999	14,999	42,077
Unrealized gains	43	43	520
Unrealized losses	0	0	0
Fair value	15,042	15,042	42,597
Pass Through Securities [Member]
Available-for-sale Securities, Balance Sheet, Reported Amounts [Abstract]
Amortized cost	146,623	146,623	116,219
Unrealized gains	2,533	2,533	1,295
Unrealized losses	0	0	(116)
Fair value	149,156	149,156	117,398
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value			29,838
12 months or more, fair value			0
Total fair value			29,838
Less than 12 months, unrealized losses			(116)
12 months or more, unrealized losses			0
Unrealized losses			(116)
Taxable state and political subdivisions [Member]
Available-for-sale Securities, Balance Sheet, Reported Amounts [Abstract]
Amortized cost	9,131	9,131	9,143
Unrealized gains	1,012	1,012	615
Unrealized losses	0	0	0
Fair value	10,143	10,143	9,758
Tax exempt states and political subdivisions [Member]
Available-for-sale Securities, Balance Sheet, Reported Amounts [Abstract]
Amortized cost	43,016	43,016	35,263
Unrealized gains	1,958	1,958	2,100
Unrealized losses	(98)	(98)	(28)
Fair value	44,876	44,876	37,335
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	7,365	7,365	1,255
12 months or more, fair value			0
Total fair value	7,365	7,365	1,255
Less than 12 months, unrealized losses	(98)	(98)	(28)
12 months or more, unrealized losses	0	0	0
Unrealized losses	(98)	(98)	(28)
Corporate obligations [Member]
Available-for-sale Securities, Balance Sheet, Reported Amounts [Abstract]
Amortized cost	11,000	11,000	11,000
Unrealized gains	0	0	0
Unrealized losses	(639)	(639)	(713)
Fair value	10,361	10,361	10,287
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	5,837	5,837	10,287
12 months or more, fair value	4,524	4,524	0
Total fair value	10,361	10,361	10,287
Less than 12 months, unrealized losses	(163)	(163)	(713)
12 months or more, unrealized losses	(476)	(476)	0
Unrealized losses	(639)	(639)	(713)
Agency-issued collateralized mortgage obligations [Member]
Available-for-sale Securities, Balance Sheet, Reported Amounts [Abstract]
Amortized cost	9,692	9,692
Unrealized gains	0	0
Unrealized losses	(65)	(65)
Fair value	9,627	9,627
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	9,627	9,627
Total fair value	9,627	9,627
Less than 12 months, unrealized losses	(65)	(65)
Unrealized losses	(65)	(65)
Investments in mutual funds and other equities [Member]
Available-for-sale Securities, Balance Sheet, Reported Amounts [Abstract]
Amortized cost	2,018	2,018	2,018
Unrealized gains	0	0	0
Unrealized losses	(14)	(14)	(12)
Fair value	2,004	2,004	2,006
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value			0
12 months or more, fair value	2,004	2,004	2,006
Total fair value	2,004	2,004	2,006
Less than 12 months, unrealized losses			0
12 months or more, unrealized losses	(14)	(14)	(12)
Unrealized losses	$ (14)	$ (14)	$ (12)