Loans And Allowance For Loan Losses (Credit Quality Of Commercial Loan Portfolio) (Details) - Commercial Portfolio Segment [Member] - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	$ 8,692,455	$ 8,624,826
Pass [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	8,409,602	8,288,517
Special Mention [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	80,797	120,368
Substandard [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	195,454	207,253
Non-Accrual [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	6,602	8,688
Business [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	4,966,722	4,958,554
Business [Member] | Pass [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	4,772,286	4,740,013
Business [Member] | Special Mention [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	40,307	59,177
Business [Member] | Substandard [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	148,998	153,417
Business [Member] | Non-Accrual [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	5,131	5,947
Real Estate - Construction And Land [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	999,691	968,820
Real Estate - Construction And Land [Member] | Pass [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	987,352	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	11,474	10,614
Real Estate - Construction And Land [Member] | Substandard [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	861	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	4	5
Real Estate - Business [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	2,726,042	2,697,452
Real Estate - Business [Member] | Pass [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	2,649,964	2,593,005
Real Estate - Business [Member] | Special Mention [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	29,016	50,577
Real Estate - Business [Member] | Substandard [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	45,595	51,134
Real Estate - Business [Member] | Non-Accrual [Member]
Loans And Allowance For Loan Losses [Line Items]
Commercial Loan Portfolio Gross Carrying Amount	$ 1,467	$ 2,736