Loans (Impaired Loans) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	$ 107,430	$ 142,416	$ 113,515
Total Recorded Investment	88,149	112,997	84,565
Related Allowance	6,564	16,692	3,904
Quarter To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	86,357	120,033	92,245
Year To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	86,357	120,033	108,914
Recorded Investment With No Allowance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment	69,351	78,237	76,952
Recorded Investment With Allowance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment	18,798	34,760	7,613
Commercial And Industrial, Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance
Total Recorded Investment
Related Allowance
Commercial And Industrial, Energy [Member] | Quarter To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment
Commercial And Industrial, Energy [Member] | Year To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment
Commercial And Industrial, Energy [Member] | Recorded Investment With No Allowance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment
Commercial And Industrial, Energy [Member] | Recorded Investment With Allowance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment
Commercial And Industrial, Other Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	55,632	70,411	57,723
Total Recorded Investment	44,736	52,987	39,331
Related Allowance	5,356	13,066	2,696
Commercial And Industrial, Other Commercial [Member] | Quarter To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	42,034	54,215	46,151
Commercial And Industrial, Other Commercial [Member] | Year To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	42,034	54,215	53,830
Commercial And Industrial, Other Commercial [Member] | Recorded Investment With No Allowance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment	28,932	27,742	34,712
Commercial And Industrial, Other Commercial [Member] | Recorded Investment With Allowance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment	15,804	25,245	4,619
Commercial Real Estate, Buildings, Land And Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	47,077	62,993	51,163
Total Recorded Investment	39,064	51,536	40,929
Related Allowance	1,113	3,626	1,113
Commercial Real Estate, Buildings, Land And Other [Member] | Quarter To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	39,996	56,671	41,522
Commercial Real Estate, Buildings, Land And Other [Member] | Year To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	39,996	56,671	48,635
Commercial Real Estate, Buildings, Land And Other [Member] | Recorded Investment With No Allowance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment	36,821	42,021	38,686
Commercial Real Estate, Buildings, Land And Other [Member] | Recorded Investment With Allowance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment	2,243	9,515	2,243
Commercial Real Estate, Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	1,551	7,124	1,568
Total Recorded Investment	1,237	6,587	1,281
Commercial Real Estate, Construction [Member] | Quarter To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	1,259	7,944	1,527
Commercial Real Estate, Construction [Member] | Year To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	1,259	7,944	4,339
Commercial Real Estate, Construction [Member] | Recorded Investment With No Allowance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment	1,237	6,587	1,281
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	2,623	1,786	2,499
Total Recorded Investment	2,577	1,786	2,470
Related Allowance	95		95
Consumer Real Estate [Member] | Quarter To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	2,524	1,152	2,484
Consumer Real Estate [Member] | Year To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	2,524	1,152	1,845
Consumer Real Estate [Member] | Recorded Investment With No Allowance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment	1,826	1,786	1,719
Consumer Real Estate [Member] | Recorded Investment With Allowance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment	751		751
Consumer And Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	547	102	562
Total Recorded Investment	535	101	554
Consumer And Other [Member] | Quarter To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	544	51	561
Consumer And Other [Member] | Year To Date [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	544	51	265
Consumer And Other [Member] | Recorded Investment With No Allowance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment	$ 535	$ 101	$ 554