Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Investment Holdings [Line Items]
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 157,344	$ 392,066
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	407	6,232
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	544,258	2,070,893
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	4,820	68,922
Available-for-sale securities, Unrealized Loss Position, Fair Value	701,602	2,462,959
Available-for-sale, Unrealized loss Position, Unrealized Losses	5,227	75,154
U.S. Treasury and agencies
Investment Holdings [Line Items]
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	47,566	0
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	226	0
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	19,956	39,656
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	42	346
Available-for-sale securities, Unrealized Loss Position, Fair Value	67,522	39,656
Available-for-sale, Unrealized loss Position, Unrealized Losses	268	346
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	5,764	59,963
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	21	800
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	1,911	38,691
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	14	1,786
Available-for-sale securities, Unrealized Loss Position, Fair Value	7,675	98,654
Available-for-sale, Unrealized loss Position, Unrealized Losses	35	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	104,014	332,103
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	160	5,432
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	522,391	1,992,546
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	4,764	66,790
Available-for-sale securities, Unrealized Loss Position, Fair Value	626,405	2,324,649
Available-for-sale, Unrealized loss Position, Unrealized Losses	$ 4,924	$ 72,222