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	Jun. 30, 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	$ (4,837)
Available-for-sale Securities, Estimated fair value, Less than 12 months	854,081
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(6,240)
Available-for-sale Securities, Estimated fair value, 12 months or more	497,398
Available-for-sale Securities, Gross unrealized losses, Total	(11,077)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	1,351,479
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(9,079)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,164,381
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(26,547)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,558,580
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(35,626)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	2,722,961
Corporate Fixed Income 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	(18)
Available-for-sale Securities, Estimated fair value, Less than 12 months	27,687
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(698)
Available-for-sale Securities, Estimated fair value, 12 months or more	134,002
Available-for-sale Securities, Gross unrealized losses, Total	(716)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	161,689
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	(4,320)
Available-for-sale Securities, Estimated fair value, Less than 12 months	776,404
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(3,887)
Available-for-sale Securities, Estimated fair value, 12 months or more	217,160
Available-for-sale Securities, Gross unrealized losses, Total	(8,207)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	993,564
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(9,079)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,164,381
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(18,684)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,027,748
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(27,763)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	2,192,129
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	(440)
Available-for-sale Securities, Estimated fair value, Less than 12 months	44,877
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(994)
Available-for-sale Securities, Estimated fair value, 12 months or more	73,702
Available-for-sale Securities, Gross unrealized losses, Total	(1,434)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	118,579
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(7,863)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	530,832
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total	(7,863)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value, Total	530,832
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	(39)
Available-for-sale Securities, Estimated fair value, Less than 12 months	4,023
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(661)
Available-for-sale Securities, Estimated fair value, 12 months or more	72,534
Available-for-sale Securities, Gross unrealized losses, Total	(700)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	76,557
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, Less than 12 months	(20)
Available-for-sale Securities, Estimated fair value, Less than 12 months	1,090
Available-for-sale Securities, Gross unrealized losses, Total	(20)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 1,090

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