Allowance for Loan Losses (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2012 item	Jun. 30, 2012	Mar. 31, 2012	Sep. 30, 2012 item	Dec. 31, 2011
Aging of recorded investment in loans by past due category and class of loans
30-59 Days Past Due	$ 11,250			$ 11,250	$ 22,571
60-89 Days Past Due	5,075			5,075	4,189
Greater than 90 days Past Due	19,635			19,635	21,325
Total Past Due	35,960			35,960	48,085
Current	1,832,638			1,832,638	1,856,199
Total	1,868,598			1,868,598	1,904,284
Allocated amount of specific reserves to customers whose loan terms have been modified in troubled debt restructurings	1,700			1,700	1,600
Loans modified in troubled debt restructurings	5,060	655	162
Number of loans defaulted that had been restructured within the past 12 months	15,000			15,000
Commercial & Industrial
Aging of recorded investment in loans by past due category and class of loans
30-59 Days Past Due	3,039			3,039	2,717
60-89 Days Past Due	802			802	740
Greater than 90 days Past Due	4,311			4,311	4,452
Total Past Due	8,152			8,152	7,909
Current	460,964			460,964	472,370
Total	469,116			469,116	480,279
Farmland
Aging of recorded investment in loans by past due category and class of loans
30-59 Days Past Due	22			22	5
60-89 Days Past Due	164			164	57
Greater than 90 days Past Due	1,325			1,325	1,034
Total Past Due	1,511			1,511	1,096
Current	88,762			88,762	98,158
Total	90,273			90,273	99,254
Non Farm, Non Residential
Aging of recorded investment in loans by past due category and class of loans
30-59 Days Past Due	812			812	2,945
60-89 Days Past Due	227			227	420
Greater than 90 days Past Due	2,753			2,753	7,754
Total Past Due	3,792			3,792	11,119
Current	315,500			315,500	310,724
Total	319,292			319,292	321,843
Amount of loans that are collateralized well enough to expect no loss	4,900
Number of loans that are collateralized well enough to expect no loss	1
Agriculture
Aging of recorded investment in loans by past due category and class of loans
30-59 Days Past Due	239			239	88
60-89 Days Past Due	191			191
Greater than 90 days Past Due	15			15	97
Total Past Due	445			445	185
Current	115,501			115,501	114,162
Total	115,946			115,946	114,347
All Other Commercial
Aging of recorded investment in loans by past due category and class of loans
30-59 Days Past Due	453			453	120
60-89 Days Past Due	57			57
Greater than 90 days Past Due	608			608	1,588
Total Past Due	1,118			1,118	1,708
Current	89,140			89,140	88,313
Total	90,258			90,258	90,021
First Liens
Aging of recorded investment in loans by past due category and class of loans
30-59 Days Past Due	1,846			1,846	11,436
60-89 Days Past Due	965			965	2,016
Greater than 90 days Past Due	4,532			4,532	5,316
Total Past Due	7,343			7,343	18,768
Current	351,053			351,053	340,269
Total	358,396			358,396	359,037
Home Equity
Aging of recorded investment in loans by past due category and class of loans
30-59 Days Past Due	119			119	175
60-89 Days Past Due	22			22	62
Greater than 90 days Past Due	19			19	8
Total Past Due	160			160	245
Current	43,750			43,750	44,939
Total	43,910			43,910	45,184
Junior Liens
Aging of recorded investment in loans by past due category and class of loans
30-59 Days Past Due	314			314	1,333
60-89 Days Past Due	199			199	183
Greater than 90 days Past Due	352			352	190
Total Past Due	865			865	1,706
Current	38,454			38,454	39,903
Total	39,319			39,319	41,609
Multifamily
Aging of recorded investment in loans by past due category and class of loans
60-89 Days Past Due	1,830			1,830	100
Greater than 90 days Past Due	5,602			5,602	668
Total Past Due	7,432			7,432	768
Current	49,219			49,219	46,216
Total	56,651			56,651	46,984
All Other Residential
Aging of recorded investment in loans by past due category and class of loans
30-59 Days Past Due					128
60-89 Days Past Due	170			170
Greater than 90 days Past Due					136
Total Past Due	170			170	264
Current	10,717			10,717	14,261
Total	10,887			10,887	14,525
Motor Vehicle
Aging of recorded investment in loans by past due category and class of loans
30-59 Days Past Due	4,189			4,189	3,450
60-89 Days Past Due	391			391	563
Greater than 90 days Past Due	112			112	77
Total Past Due	4,692			4,692	4,090
Current	245,730			245,730	260,102
Total	250,422			250,422	264,192
All Other Consumer
Aging of recorded investment in loans by past due category and class of loans
30-59 Days Past Due	217			217	174
60-89 Days Past Due	57			57	48
Greater than 90 days Past Due	6			6	5
Total Past Due	280			280	227
Current	23,848			23,848	26,782
Total	24,128			24,128	27,009
Amount of loans that are collateralized well enough to expect no loss	$ 126