Available-for-Sale and Held-to-Maturity Securities (Schedule of Amortized Cost of Held-to-Maturity Securities by Credit Quality Indicator) (Details) - USD ($) $ in Thousands |
Mar. 31, 2026 |
Dec. 31, 2025 |
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|---|---|---|---|---|
| Schedule Of Held To Maturity Securities [Line Items] | ||||
| Held-to-maturity securities, at amortized cost | [1] | $ 6,861,227 | $ 6,549,054 | |
| Asset-Backed Securities [Member] | ||||
| Schedule Of Held To Maturity Securities [Line Items] | ||||
| Held-to-maturity securities, at amortized cost | 6,861,227 | |||
| Asset-Backed Securities [Member] | AAA [Member] | ||||
| Schedule Of Held To Maturity Securities [Line Items] | ||||
| Held-to-maturity securities, at amortized cost | 4,164,284 | |||
| Asset-Backed Securities [Member] | AA [Member] | ||||
| Schedule Of Held To Maturity Securities [Line Items] | ||||
| Held-to-maturity securities, at amortized cost | $ 2,696,943 | |||
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