Loans (Weighted Average Risk Grades For All Commercial Loans By Class) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Risk Grade 9 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk Grade	9
Risk Grade 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk Grade	10
Risk Grade 11 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk Grade	11
Risk Grade 12 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk Grade	12
Risk Grade 13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk Grade	13
Risk Grade 14 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk Grade	14
Minimum [Member] | Risk Grades 1-8 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk Grade	1
Commercial And Industrial, Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	5.38	5.36	5.22
Loans	$ 994,979	$ 761,570	$ 870,586
Commercial And Industrial, Energy [Member] | Risk Grades 1-8 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	5.37	5.35	5.21
Loans	992,463	760,093	868,561
Commercial And Industrial, Energy [Member] | Risk Grade 9 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	9.00	9.00	9.00
Loans	2,516	1,477	2,025
Commercial And Industrial, Energy [Member] | Risk Grade 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	10.00	10.00	10.00
Commercial And Industrial, Energy [Member] | Risk Grade 11 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	11.00	11.00	11.00
Commercial And Industrial, Energy [Member] | Risk Grade 12 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	12.00	12.00	12.00
Commercial And Industrial, Energy [Member] | Risk Grade 13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	13.00	13.00	13.00
Commercial And Industrial, Other Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	6.55	6.75	6.55
Loans	3,047,873	2,961,674	3,046,281
Commercial And Industrial, Other Commercial [Member] | Risk Grades 1-8 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	6.20	6.22	6.20
Loans	2,803,976	2,590,198	2,802,037
Commercial And Industrial, Other Commercial [Member] | Risk Grade 9 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	9.00	9.00	9.00
Loans	65,376	101,576	55,105
Commercial And Industrial, Other Commercial [Member] | Risk Grade 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	10.00	10.00	10.00
Loans	35,504	98,865	49,982
Commercial And Industrial, Other Commercial [Member] | Risk Grade 11 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	11.00	11.00	11.00
Loans	93,415	111,514	96,046
Commercial And Industrial, Other Commercial [Member] | Risk Grade 12 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	12.00	12.00	12.00
Loans	44,520	35,636	39,826
Commercial And Industrial, Other Commercial [Member] | Risk Grade 13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	13.00	13.00	13.00
Loans	5,082	23,885	3,285
Commercial Real Estate, Buildings, Land And Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	7.12	7.23	7.14
Loans	2,541,284	2,638,057	2,585,957
Commercial Real Estate, Buildings, Land And Other [Member] | Risk Grades 1-8 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	6.67	6.71	6.69
Loans	2,233,155	2,253,835	2,266,576
Commercial Real Estate, Buildings, Land And Other [Member] | Risk Grade 9 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	9.00	9.00	9.00
Loans	104,727	138,117	103,894
Commercial Real Estate, Buildings, Land And Other [Member] | Risk Grade 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	10.00	10.00	10.00
Loans	33,641	79,306	45,278
Commercial Real Estate, Buildings, Land And Other [Member] | Risk Grade 11 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	11.00	11.00	11.00
Loans	127,869	101,357	126,594
Commercial Real Estate, Buildings, Land And Other [Member] | Risk Grade 12 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	12.00	12.00	12.00
Loans	40,486	58,064	41,747
Commercial Real Estate, Buildings, Land And Other [Member] | Risk Grade 13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	13.00	13.00	13.00
Loans	1,406	7,378	1,868
Commercial Real Estate, Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	7.19	7.53	7.30
Loans	493,600	574,637	434,870
Commercial Real Estate, Construction [Member] | Risk Grades 1-8 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	6.97	7.15	6.95
Loans	454,674	497,355	378,530
Commercial Real Estate, Construction [Member] | Risk Grade 9 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	9.00	9.00	9.00
Loans	16,062	28,173	30,376
Commercial Real Estate, Construction [Member] | Risk Grade 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	10.00	10.00	10.00
Loans	15,442	30,128	16,186
Commercial Real Estate, Construction [Member] | Risk Grade 11 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	11.00	11.00	11.00
Loans	6,137	12,170	8,449
Commercial Real Estate, Construction [Member] | Risk Grade 12 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	12.00	12.00	12.00
Loans	1,285	6,587	1,329
Commercial Real Estate, Construction [Member] | Risk Grade 13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	13.00	13.00	13.00
Commercial Real Estate, Construction [Member] | Risk Grade 14 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Risk Grade	14.00	14.00	14.00
Loans		$ 224