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Available-for-Sale and Held-to-Maturity Securities (Schedule of Amortized Cost and Fair Values of Available for Sale Securities and Held to Maturity Securities) (Details) - USD ($) $ in Thousands | Sep. 30, 2023 | Dec. 31, 2022
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Schedule Of Available For Sale And Held To Maturity Securities [Line Items] |  |  |  |
Available-for-sale Securities, Amortized Cost |  | $ 1,762,739 |  | $ 1,863,219
Available for sale securities, Gross Unrealized Gains | [1] | 5 |  | 151
Available-for-sale Securities, Gross Unrealized Losses | [1] | (250,511) |  | (227,329)
Available-for-sale securities, Fair Value |  | 1,512,233 | [2] | 1,636,041
Held-to-maturity Securities, Amortized cost | [3] | 5,900,379 |  | 5,990,451
Held-to-maturity Securities, Gross unrealized gains | [1],[3] | 5,476 |  | 3,213
Held-to-maturity Securities, Gross unrealized losses | [1],[3] | (94,255) |  | (255,246)
Held-to-maturity securities, Estimated Fair Value | [3] | 5,811,600 |  | 5,738,418
U.S. Government Agency Securities [Member] |  |  |  |
Schedule Of Available For Sale And Held To Maturity Securities [Line Items] |  |  |  |
Available-for-sale Securities, Amortized Cost |  | 2,368 |  | 2,345
Available for sale securities, Gross Unrealized Gains | [1] | 0 |  | 6
Available-for-sale Securities, Gross Unrealized Losses | [1] | (233) |  | (203)
Available-for-sale securities, Fair Value |  | 2,135 |  | 2,148
State and Municipal Securities [Member] |  |  |  |
Schedule Of Available For Sale And Held To Maturity Securities [Line Items] |  |  |  |
Available-for-sale Securities, Amortized Cost |  | 2,350 |  | 2,350
Available for sale securities, Gross Unrealized Gains | [1] | 0 |  | 1
Available-for-sale Securities, Gross Unrealized Losses | [1] | (56) |  | 0
Available-for-sale securities, Fair Value |  | 2,294 |  | 2,351
Mortgage-Backed Securities [Member] | Agency Securities [Member] |  |  |  |
Schedule Of Available For Sale And Held To Maturity Securities [Line Items] |  |  |  |
Available-for-sale Securities, Amortized Cost |  | 876,007 |  | 921,676
Available for sale securities, Gross Unrealized Gains | [1] | 0 |  | 0
Available-for-sale Securities, Gross Unrealized Losses | [1] | (160,757) |  | (130,654)
Available-for-sale securities, Fair Value |  | 715,250 | [2] | 791,022
Mortgage-Backed Securities [Member] | Commercial [Member] |  |  |  |
Schedule Of Available For Sale And Held To Maturity Securities [Line Items] |  |  |  |
Available-for-sale Securities, Amortized Cost |  | 70,563 |  | 71,462
Available for sale securities, Gross Unrealized Gains | [1] | 0 |  | 0
Available-for-sale Securities, Gross Unrealized Losses | [1] | (4,868) |  | (5,349)
Available-for-sale securities, Fair Value |  | 65,695 | [2] | 66,113
Mortgage-Backed Securities [Member] | Non-Agency [Member] |  |  |  |
Schedule Of Available For Sale And Held To Maturity Securities [Line Items] |  |  |  |
Available-for-sale Securities, Amortized Cost |  | 351 |  | 442
Available for sale securities, Gross Unrealized Gains | [1] | 0 |  | 0
Available-for-sale Securities, Gross Unrealized Losses | [1] | (19) |  | (54)
Available-for-sale securities, Fair Value |  | 332 | [2] | 388
Corporate Fixed Income Securities [Member] |  |  |  |
Schedule Of Available For Sale And Held To Maturity Securities [Line Items] |  |  |  |
Available-for-sale Securities, Amortized Cost |  | 618,164 |  | 643,379
Available for sale securities, Gross Unrealized Gains | [1] | 5 |  | 18
Available-for-sale Securities, Gross Unrealized Losses | [1] | (80,319) |  | (77,103)
Available-for-sale securities, Fair Value |  | 537,850 |  | 566,294
Asset-Backed Securities [Member] |  |  |  |
Schedule Of Available For Sale And Held To Maturity Securities [Line Items] |  |  |  |
Available-for-sale Securities, Amortized Cost |  | 192,936 |  | 221,565
Available for sale securities, Gross Unrealized Gains | [1] | 0 |  | 126
Available-for-sale Securities, Gross Unrealized Losses | [1] | (4,259) |  | (13,966)
Available-for-sale securities, Fair Value |  | 188,677 | [2] | $ 207,725
Held-to-maturity Securities, Amortized cost |  | $ 5,900,379 |  |
[1] | Unrealized gains/(losses) related to available-for-sale securities are reported in accumulated other comprehensive income.
[2] | Due to the immaterial amount of income recognized on tax-exempt securities, yields were not calculated on a tax-equivalent basis.
[3] | Held-to-maturity securities are carried in the consolidated statements of financial condition at amortized cost, and the changes in the value of these securities, other than impairment charges, are not reported on the consolidated financial statements.

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