Loans And Allowance For Loan Losses (Credit Quality Of Commercial Loan Portfolio) (Details) - Commercial Portfolio Segment [Member] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	$ 8,617,256	$ 8,624,826
Pass [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	8,268,003	8,288,517
Special Mention [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	150,061	120,368
Substandard [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	191,084	207,253
Non-Accrual [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	8,108	8,688
Business [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	4,960,614	4,958,554
Business [Member] | Pass [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	4,716,879	4,740,013
Business [Member] | Special Mention [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	88,442	59,177
Business [Member] | Substandard [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	149,736	153,417
Business [Member] | Non-Accrual [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	5,557	5,947
Real Estate - Construction And Land [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	932,058	968,820
Real Estate - Construction And Land [Member] | Pass [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	919,050	955,499
Real Estate - Construction And Land [Member] | Special Mention [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	10,694	10,614
Real Estate - Construction And Land [Member] | Substandard [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	2,309	2,702
Real Estate - Construction And Land [Member] | Non-Accrual [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	5	5
Real Estate - Business [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	2,724,584	2,697,452
Real Estate - Business [Member] | Pass [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	2,632,074	2,593,005
Real Estate - Business [Member] | Special Mention [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	50,925	50,577
Real Estate - Business [Member] | Substandard [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	39,039	51,134
Real Estate - Business [Member] | Non-Accrual [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	$ 2,546	$ 2,736