Allowance For Loan Losses (Schedule Of Non-Commercial Loans By Payment Performance) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Total	$ 3,137,681	$ 3,127,410
Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Total	1,465,215	1,468,278
Residential real estate | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,461,802	1,465,445
Residential real estate | Non-Performing
Financing Receivable, Recorded Investment [Line Items]
Total	3,413	2,833
Home equity
Financing Receivable, Recorded Investment [Line Items]
Total	138,477	139,499
Home equity | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	138,341	139,239
Home equity | Non-Performing
Financing Receivable, Recorded Investment [Line Items]
Total	136	260
Consumer
Financing Receivable, Recorded Investment [Line Items]
Total	29,570	29,162
Consumer | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	29,570	29,162
Consumer | Non-Performing
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
DDA overdrafts
Financing Receivable, Recorded Investment [Line Items]
Total	3,523	4,411
DDA overdrafts | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,523	4,411
DDA overdrafts | Non-Performing
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Total
Financing Receivable, Recorded Investment [Line Items]
Total	1,636,785	1,641,350
Total | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,633,236	1,638,257
Total | Non-Performing
Financing Receivable, Recorded Investment [Line Items]
Total	$ 3,549	$ 3,093