Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Investment Holdings [Line Items]
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 47,698	$ 392,066
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	274	6,232
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	1,121,451	2,070,893
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	13,115	68,922
Available-for-sale securities, Unrealized Loss Position, Fair Value	1,169,149	2,462,959
Available-for-sale, Unrealized loss Position, Unrealized Losses	13,389	75,154
U.S. Treasury and agencies
Investment Holdings [Line Items]
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	9,091	0
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	62	0
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	19,919	39,656
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	79	346
Available-for-sale securities, Unrealized Loss Position, Fair Value	29,010	39,656
Available-for-sale, Unrealized loss Position, Unrealized Losses	141	346
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	865	59,963
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	1	800
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	17,516	38,691
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	168	1,786
Available-for-sale securities, Unrealized Loss Position, Fair Value	18,381	98,654
Available-for-sale, Unrealized loss Position, Unrealized Losses	169	2,586
Residential mortgage-backed securities and collateralized mortgage obligations
Investment Holdings [Line Items]
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	37,742	332,103
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	211	5,432
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	1,084,016	1,992,546
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	12,868	66,790
Available-for-sale securities, Unrealized Loss Position, Fair Value	1,121,758	2,324,649
Available-for-sale, Unrealized loss Position, Unrealized Losses	$ 13,079	$ 72,222