Loans (Age Analysis Of Past Due Loans, Segregated By Class Of Loans) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-89 Days Past Due	$ 47,334
Loans 90 or More Days Past Due	52,542
Total Past Due Loans	99,876
Current Loans	8,026,837
Total Loans	8,126,713	7,995,129	8,025,080
Accruing Loans 90 or More Days Past Due	20,618
Commercial And Industrial, Energy [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-89 Days Past Due
Loans 90 or More Days Past Due
Total Past Due Loans
Current Loans	994,979
Total Loans	994,979
Accruing Loans 90 or More Days Past Due
Commercial And Industrial, Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-89 Days Past Due	13,297
Loans 90 or More Days Past Due	21,651
Total Past Due Loans	34,948
Current Loans	3,012,925
Total Loans	3,047,873
Accruing Loans 90 or More Days Past Due	6,805
Commercial Real Estate, Buildings, Land And Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-89 Days Past Due	23,678
Loans 90 or More Days Past Due	24,308
Total Past Due Loans	47,986
Current Loans	2,493,298
Total Loans	2,541,284
Accruing Loans 90 or More Days Past Due	9,473
Commercial Real Estate, Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-89 Days Past Due	1,247
Loans 90 or More Days Past Due	1,791
Total Past Due Loans	3,038
Current Loans	490,562
Total Loans	493,600
Accruing Loans 90 or More Days Past Due	1,743
Consumer Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-89 Days Past Due	5,565
Loans 90 or More Days Past Due	4,504
Total Past Due Loans	10,069
Current Loans	751,217
Total Loans	761,286
Accruing Loans 90 or More Days Past Due	2,408
Consumer And Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-89 Days Past Due	3,547
Loans 90 or More Days Past Due	288
Total Past Due Loans	3,835
Current Loans	300,637
Total Loans	304,472
Accruing Loans 90 or More Days Past Due	189
Unearned Discounts [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-89 Days Past Due
Loans 90 or More Days Past Due
Total Past Due Loans
Current Loans	(16,781)
Total Loans	(16,781)
Accruing Loans 90 or More Days Past Due