Loans and the Allowance for Credit Losses (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Allowance for Credit Losses and Recorded Investments in Loans
Allowance for loans individually evaluated for impairment	$ 3,582	$ 3,353
Allowance for loans collectively evaluated for impairment	50,028	51,457
Allowance for Loan Commitments	351	468	705	1,404
Total allowance for credit losses	53,961	55,278	62,123	62,455
Individually evaluated for impairment	21,609	28,843
Collectively evaluated for impairment	3,254,221	3,210,525
Total portfolio loans	3,275,830	3,239,368
Commercial Real Estate Land and Construction [Member]
Allowance for Credit Losses and Recorded Investments in Loans
Allowance for loans individually evaluated for impairment	1,675	1,788
Allowance for loans collectively evaluated for impairment	2,800	3,054
Allowance for Loan Commitments	49	74	341	1,037
Total allowance for credit losses	4,524	4,916	5,436	5,738
Individually evaluated for impairment	4,933	10,815
Collectively evaluated for impairment	153,480	165,052
Total portfolio loans	158,413	175,867
Commercial Real Estate Improved Property [Member]
Allowance for Credit Losses and Recorded Investments in Loans
Allowance for loans individually evaluated for impairment	1,907	1,565
Allowance for loans collectively evaluated for impairment	22,814	23,183
Allowance for Loan Commitments	10	21	10	285
Total allowance for credit losses	24,731	24,769	30,611	31,121
Individually evaluated for impairment	16,676	18,028
Collectively evaluated for impairment	1,519,956	1,491,670
Total portfolio loans	1,536,632	1,509,698
Commercial and Industrial [Member]
Allowance for Credit Losses and Recorded Investments in Loans
Allowance for loans individually evaluated for impairment	0	0
Allowance for loans collectively evaluated for impairment	10,068	11,414
Allowance for Loan Commitments	224	323	300	65
Total allowance for credit losses	10,292	11,737	11,624	10,858
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	420,689	426,315
Total portfolio loans	420,689	426,315
Residential Real Estate [Member]
Allowance for Credit Losses and Recorded Investments in Loans
Allowance for loans individually evaluated for impairment	0	0
Allowance for loans collectively evaluated for impairment	5,780	5,638
Allowance for Loan Commitments	5	4	2	1
Total allowance for credit losses	5,785	5,642	5,594	5,951
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	662,556	621,383
Total portfolio loans	662,556	621,383
Home Equity [Member]
Allowance for Credit Losses and Recorded Investments in Loans
Allowance for loans individually evaluated for impairment	0	0
Allowance for loans collectively evaluated for impairment	2,441	1,962
Allowance for Loan Commitments	48	33	38	14
Total allowance for credit losses	2,489	1,995	2,093	2,087
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	250,988	251,785
Total portfolio loans	250,988	251,785
Consumer [Member]
Allowance for Credit Losses and Recorded Investments in Loans
Allowance for loans individually evaluated for impairment	0	0
Allowance for loans collectively evaluated for impairment	5,419	5,410
Allowance for Loan Commitments	15	13	14	2
Total allowance for credit losses	5,434	5,423	5,380	5,643
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	246,552	254,320
Total portfolio loans	246,552	254,320
Overdraft [Member]
Allowance for Credit Losses and Recorded Investments in Loans
Allowance for loans individually evaluated for impairment	0	0
Allowance for loans collectively evaluated for impairment	706	796
Allowance for Loan Commitments	0	0	0	0
Total allowance for credit losses	706	796	1,385	1,057
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	0	0
Total portfolio loans	$ 0	$ 0