Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Investment Holdings [Line Items]
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 140,819	$ 606,646
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	184	5,982
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	0	404,708
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	0	4,065
Available-for-sale securities, Unrealized Loss Position, Fair Value	140,819	1,011,354
Available-for-sale, Unrealized loss Position, Unrealized Losses	184	10,047
U.S. Treasury and agencies
Investment Holdings [Line Items]
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value		313,169
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses		4,324
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		0
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses		0
Available-for-sale securities, Unrealized Loss Position, Fair Value		313,169
Available-for-sale, Unrealized loss Position, Unrealized Losses		4,324
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	16,729	4,611
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	66	30
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	0	1,906
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	0	7
Available-for-sale securities, Unrealized Loss Position, Fair Value	16,729	6,517
Available-for-sale, Unrealized loss Position, Unrealized Losses	66	37
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	124,090	288,866
Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	118	1,628
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	0	402,802
Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses	0	4,058
Available-for-sale securities, Unrealized Loss Position, Fair Value	124,090	691,668
Available-for-sale, Unrealized loss Position, Unrealized Losses	$ 118	$ 5,686