Available-For-Sale And Held-To-Maturity Securities (Schedule Of Gross Unrealized Losses And The Estimated Fair Value By Length Of Time In A Loss Position) (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	$ (8,321)
Available-for-sale Securities, Estimated fair value, Less than 12 months	913,040
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(6,472)
Available-for-sale Securities, Estimated fair value, 12 months or more	711,129
Available-for-sale Securities, Gross unrealized losses, Total	(14,793)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	1,624,169
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(31,400)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(34,300)
Asset-Backed Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(3,056)
Available-for-sale Securities, Estimated fair value, Less than 12 months	349,095
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(5,149)
Available-for-sale Securities, Estimated fair value, 12 months or more	596,161
Available-for-sale Securities, Gross unrealized losses, Total	(8,205)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	945,256
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(2,915)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	346,069
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(31,381)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,980,673
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(34,296)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	2,326,742
Mortgage Backed Securities [Member] \| Agency [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(4,571)
Available-for-sale Securities, Estimated fair value, Less than 12 months	458,861
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(1,280)
Available-for-sale Securities, Estimated fair value, 12 months or more	112,001
Available-for-sale Securities, Gross unrealized losses, Total	(5,851)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	570,862
Mortgage Backed Securities [Member] \| Commercial [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	(694)
Available-for-sale Securities, Estimated fair value, Less than 12 months	105,084
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(20)
Available-for-sale Securities, Estimated fair value, 12 months or more	2,001
Available-for-sale Securities, Gross unrealized losses, Total	(714)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	107,085
Mortgage Backed Securities [Member] \| Non-Agency [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(23)
Available-for-sale Securities, Estimated fair value, 12 months or more	966
Available-for-sale Securities, Gross unrealized losses, Total	(23)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 966

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