Loans (Weighted Average Risk Grades for Loans and Classified Loan Amounts) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Minimum [Member] | Risk Grades 1-8 [Member]
Risk Grade	1
Maximum [Member] | Risk Grades 1-8 [Member]
Risk Grade	8
Commercial And Industrial, Energy [Member] | Risk Grades 1-8 [Member]
Weighted Average Risk Grade	5.36	5.16	5.27
Loans	$ 800,855	$ 689,847	$ 786,664
Commercial And Industrial, Other Commercial [Member] | Risk Grades 1-8 [Member]
Weighted Average Risk Grade	6.17	6.24	6.16
Loans	2,648,041	2,458,563	2,572,011
Commercial Real Estate, Buildings, Land And Other [Member] | Risk Grades 1-8 [Member]
Weighted Average Risk Grade	6.68	6.74	6.71
Loans	2,282,540	2,185,007	2,189,602
Commercial Real Estate, Construction [Member] | Risk Grades 1-8 [Member]
Weighted Average Risk Grade	7.04	7.17	7.10
Loans	455,036	486,339	485,455
Commercial And Industrial, Energy [Member] | Risk Grade 9 [Member]
Weighted Average Risk Grade	9.00	9.00	9.00
Loans	1,477	56,173	20,224
Commercial And Industrial, Other Commercial [Member] | Risk Grade 9 [Member]
Weighted Average Risk Grade	9.00	9.00	9.00
Loans	146,112	129,347	95,278
Commercial Real Estate, Buildings, Land And Other [Member] | Risk Grade 9 [Member]
Weighted Average Risk Grade	9.00	9.00	9.00
Loans	113,400	106,194	137,314
Commercial Real Estate, Construction [Member] | Risk Grade 9 [Member]
Weighted Average Risk Grade	9.00	9.00	9.00
Loans	26,637	32,454	52,817
Risk Grade 9 [Member]
Risk Grade	9
Commercial And Industrial, Energy [Member] | Risk Grade 10 [Member]
Weighted Average Risk Grade	10.00	10.00	10.00
Loans
Commercial And Industrial, Other Commercial [Member] | Risk Grade 10 [Member]
Weighted Average Risk Grade	10.00	10.00	10.00
Loans	51,458	117,557	116,158
Commercial Real Estate, Buildings, Land And Other [Member] | Risk Grade 10 [Member]
Weighted Average Risk Grade	10.00	10.00	10.00
Loans	73,031	130,670	91,962
Commercial Real Estate, Construction [Member] | Risk Grade 10 [Member]
Weighted Average Risk Grade	10.00	10.00	10.00
Loans	34,332	28,892	32,055
Risk Grade 10 [Member]
Risk Grade	10
Commercial And Industrial, Energy [Member] | Risk Grade 11 [Member]
Weighted Average Risk Grade	11.00	11.00	11.00
Loans
Commercial And Industrial, Other Commercial [Member] | Risk Grade 11 [Member]
Weighted Average Risk Grade	11.00	11.00	11.00
Loans	119,946	181,195	137,923
Commercial Real Estate, Buildings, Land And Other [Member] | Risk Grade 11 [Member]
Weighted Average Risk Grade	11.00	11.00	11.00
Loans	105,209	111,954	126,403
Commercial Real Estate, Construction [Member] | Risk Grade 11 [Member]
Weighted Average Risk Grade	11.00	11.00	11.00
Loans	14,185	30,161	13,646
Risk Grade 11 [Member]
Risk Grade	11
Commercial And Industrial, Energy [Member] | Risk Grade 12 [Member]
Weighted Average Risk Grade	12.00	12.00	12.00
Loans		1,430
Commercial And Industrial, Other Commercial [Member] | Risk Grade 12 [Member]
Weighted Average Risk Grade	12.00	12.00	12.00
Loans	52,428	37,499	48,216
Commercial Real Estate, Buildings, Land And Other [Member] | Risk Grade 12 [Member]
Weighted Average Risk Grade	12.00	12.00	12.00
Loans	47,484	66,774	54,366
Commercial Real Estate, Construction [Member] | Risk Grade 12 [Member]
Weighted Average Risk Grade	12.00	12.00	12.00
Loans	2,942	7,568	9,300
Risk Grade 12 [Member]
Risk Grade	12
Commercial And Industrial, Energy [Member] | Risk Grade 13 [Member]
Weighted Average Risk Grade	13.00	13.00	13.00
Loans
Commercial And Industrial, Other Commercial [Member] | Risk Grade 13 [Member]
Weighted Average Risk Grade	13.00	13.00	13.00
Loans	21,833	18,461	12,184
Commercial Real Estate, Buildings, Land And Other [Member] | Risk Grade 13 [Member]
Weighted Average Risk Grade	13.00	13.00	13.00
Loans	2,303	8,331	9,847
Commercial Real Estate, Construction [Member] | Risk Grade 13 [Member]
Weighted Average Risk Grade	13.00	13.00	13.00
Loans		254
Risk Grade 13 [Member]
Risk Grade	13
Commercial And Industrial, Energy [Member]
Weighted Average Risk Grade	5.37	5.46	5.36
Loans	802,332	747,450	806,888
Commercial And Industrial, Other Commercial [Member]
Weighted Average Risk Grade	6.71	6.92	6.75
Loans	3,039,818	2,942,622	2,981,770
Commercial Real Estate, Buildings, Land And Other [Member]
Weighted Average Risk Grade	7.15	7.34	7.29
Loans	2,623,967	2,608,930	2,609,494
Commercial Real Estate, Construction [Member]
Weighted Average Risk Grade	7.46	7.67	7.59
Loans	$ 533,132	$ 585,668	$ 593,273