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Investment Securities - Expected Maturities of Investment Securities Portfolio (Detail) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Available-for-sale, Amortized Cost |  |
Within one year | $ 126,291 |
One to five years | 2,208,550 |
Five to ten years | 2,015,116 |
Beyond ten years | 2,310,263 |
Total | 6,660,220 | $ 5,784,754
Available-for-sale, Fair Value |  |
Within one year | 127,635 |
One to five years | 2,271,071 |
Five to ten years | 2,005,310 |
Beyond ten years | 2,320,514 |
Total | $ 6,724,530 | $ 5,970,115
Available-for-sale, Weighted Average Yield |  |
Within one year | 2.86% |
One to five years | 2.43% |
Five to ten years | 1.77% |
Beyond ten years | 2.45% |
Total | 2.25% |

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