Available-for-Sale and Held-to-Maturity Securities (Schedule of Gross Unrealized Losses and Estimated Fair Value by Length of Time) (Details) $ in Thousands	Sep. 30, 2023 USD ($)
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Gross unrealized losses, Less than 12 months	$ (3,176)
Available-for-sale Securities, Estimated fair value, Less than 12 months	97,267
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(247,335)
Available-for-sale Securities, Estimated fair value, 12 months or more	1,412,468
Available-for-sale Securities, Gross unrealized losses, Total	(250,511)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	1,509,735
U.S. Government Agency 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	(8)
Available-for-sale Securities, Estimated fair value, Less than 12 months	427
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(225)
Available-for-sale Securities, Estimated fair value, 12 months or more	1,708
Available-for-sale Securities, Gross unrealized losses, Total	(233)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	2,135
State and Municipal 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	(56)
Available-for-sale Securities, Estimated fair value, Less than 12 months	2,294
Available-for-sale Securities, Gross unrealized losses, 12 months or more	0
Available-for-sale Securities, Estimated fair value, 12 months or more	0
Available-for-sale Securities, Gross unrealized losses, Total	(56)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	2,294
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	(235)
Available-for-sale Securities, Estimated fair value, Less than 12 months	6,438
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(80,084)
Available-for-sale Securities, Estimated fair value, 12 months or more	528,914
Available-for-sale Securities, Gross unrealized losses, Total	(80,319)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	535,352
Mortgage-Backed Securities [Member] \| Agency 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	(1,228)
Available-for-sale Securities, Estimated fair value, Less than 12 months	24,100
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(159,529)
Available-for-sale Securities, Estimated fair value, 12 months or more	691,150
Available-for-sale Securities, Gross unrealized losses, Total	(160,757)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	715,250
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	0
Available-for-sale Securities, Estimated fair value, Less than 12 months	0
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(4,868)
Available-for-sale Securities, Estimated fair value, 12 months or more	65,695
Available-for-sale Securities, Gross unrealized losses, Total	(4,868)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	65,695
Mortgage-Backed Securities [Member] \| Non Agency Mortgage 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	0
Available-for-sale Securities, Estimated fair value, Less than 12 months	0
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(19)
Available-for-sale Securities, Estimated fair value, 12 months or more	332
Available-for-sale Securities, Gross unrealized losses, Total	(19)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	332
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	(1,649)
Available-for-sale Securities, Estimated fair value, Less than 12 months	64,008
Available-for-sale Securities, Gross unrealized losses, 12 months or more	(2,610)
Available-for-sale Securities, Estimated fair value, 12 months or more	124,669
Available-for-sale Securities, Gross unrealized losses, Total	(4,259)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 188,677

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