Loans and the Allowance for Credit Losses (Details 4) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Summary of age analysis of Loan Categories
Current	$ 3,224,477	$ 3,166,712
30-59 days past due	12,696	19,554
60-89 days past due	5,633	6,569
90 days or more past due	33,024	46,533
Total past due	51,353	72,656
Total portfolio loans	3,275,830	3,239,368
90 days or more past due and accruing	3,639	5,135
Loans held for sale	7,305	6,084
Total loans, current	3,231,782	3,172,796
Total loans	3,283,135	3,245,452
Nonaccrual Loans [Member]
Summary of age analysis of Loan Categories
Current	8,698	12,377
30-59 days past due	837	1,629
60-89 days past due	1,169	2,818
90 days or more past due	29,248	40,668
Total past due	31,254	45,115
Total portfolio loans	39,952	57,492
TDRS [Member]
Summary of age analysis of Loan Categories
Current	26,822	26,893
30-59 days past due	884	1,434
60-89 days past due	322	354
90 days or more past due	137	730
Total past due	1,343	2,518
Total portfolio loans	28,165	29,411
Commercial Real Estate Land and Construction [Member]
Summary of age analysis of Loan Categories
Current	152,694	166,322
30-59 days past due	15	1,391
60-89 days past due	353	127
90 days or more past due	5,351	8,027
Total past due	5,719	9,545
Total portfolio loans	158,413	175,867
90 days or more past due and accruing	416	0
Commercial Real Estate Improved Property [Member]
Summary of age analysis of Loan Categories
Current	1,520,114	1,486,001
30-59 days past due	2,462	4,485
60-89 days past due	1,734	3,446
90 days or more past due	12,322	15,766
Total past due	16,518	23,697
Total portfolio loans	1,536,632	1,509,698
90 days or more past due and accruing	98	18
Commercial Real Estate [Member]
Summary of age analysis of Loan Categories
Current	1,672,808	1,652,323
30-59 days past due	2,477	5,876
60-89 days past due	2,087	3,573
90 days or more past due	17,673	23,793
Total past due	22,237	33,242
Total portfolio loans	1,695,045	1,685,565
90 days or more past due and accruing	514	18
Commercial and Industrial [Member]
Summary of age analysis of Loan Categories
Current	415,707	417,341
30-59 days past due	630	1,624
60-89 days past due	884	333
90 days or more past due	3,468	7,017
Total past due	4,982	8,974
Total portfolio loans	420,689	426,315
90 days or more past due and accruing	177	939
Residential Real Estate [Member]
Summary of age analysis of Loan Categories
Current	646,326	601,541
30-59 days past due	4,749	5,742
60-89 days past due	1,656	1,186
90 days or more past due	9,825	12,914
Total past due	16,230	19,842
Total portfolio loans	662,556	621,383
90 days or more past due and accruing	1,752	2,881
Home Equity [Member]
Summary of age analysis of Loan Categories
Current	247,634	247,771
30-59 days past due	1,430	1,843
60-89 days past due	304	447
90 days or more past due	1,620	1,724
Total past due	3,354	4,014
Total portfolio loans	250,988	251,785
90 days or more past due and accruing	902	498
Consumer [Member]
Summary of age analysis of Loan Categories
Current	242,002	247,736
30-59 days past due	3,410	4,469
60-89 days past due	702	1,030
90 days or more past due	438	1,085
Total past due	4,550	6,584
Total portfolio loans	246,552	254,320
90 days or more past due and accruing	294	799
Loans held for sale [Member]
Summary of age analysis of Loan Categories
30-59 days past due	0
60-89 days past due	0
90 days or more past due	0
Total past due	0
90 days or more past due and accruing	0
Loans held for sale, current	$ 7,305	$ 6,084