Loans And Allowance For Loan Losses (Credit Quality Of Commercial Loan Portfolio) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	$ 8,624,826	$ 8,210,975
Pass [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	8,288,517	7,939,679
Special Mention [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	120,368	162,843
Substandard [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	207,253	97,573
Non-Accrual [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	8,688	10,880
Business [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	4,958,554	4,776,365
Real Estate - Construction And Land [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	968,820	791,236
Real Estate - Business [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	2,697,452	2,643,374
Commercial Portfolio Segment [Member] | Business [Member] | Pass [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	4,740,013	4,607,553
Commercial Portfolio Segment [Member] | Business [Member] | Special Mention [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	59,177	116,642
Commercial Portfolio Segment [Member] | Business [Member] | Substandard [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	153,417	43,488
Commercial Portfolio Segment [Member] | Business [Member] | Non-Accrual [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	5,947	8,682
Commercial Portfolio Segment [Member] | Real Estate - Construction And Land [Member] | Pass [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	955,499	788,778
Commercial Portfolio Segment [Member] | Real Estate - Construction And Land [Member] | Special Mention [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	10,614	722
Commercial Portfolio Segment [Member] | Real Estate - Construction And Land [Member] | Substandard [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	2,702	1,172
Commercial Portfolio Segment [Member] | Real Estate - Construction And Land [Member] | Non-Accrual [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	5	564
Commercial Portfolio Segment [Member] | Real Estate - Business [Member] | Pass [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	2,593,005	2,543,348
Commercial Portfolio Segment [Member] | Real Estate - Business [Member] | Special Mention [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	50,577	45,479
Commercial Portfolio Segment [Member] | Real Estate - Business [Member] | Substandard [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	51,134	52,913
Commercial Portfolio Segment [Member] | Real Estate - Business [Member] | Non-Accrual [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	$ 2,736	$ 1,634