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Borrowings, Short-Term Borrowings (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Short-term borrowings [Abstract] |  |  |
Balance at year-end | $ 168,386 | $ 655,275 |
FHLB, unused lines of credit available for short-term financing | 3,100,000 | 2,400,000 |
Federal Funds Purchased [Member] |  |  |
Short-term borrowings [Abstract] |  |  |
Balance at year-end | 0 | 65,000 | $ 80,000
Average during the year | 14,727 | 47,137 | 66,839
Maximum month end balance | $ 40,000 | $ 80,000 | $ 80,000
Weighted average rate during the year | 2.05% | 3.90% | 3.43%
Weighted average rate at year-end | 0.00% | 2.84% | 4.25%
Securities Sold Under Repurchase Agreements [Member] |  |  |
Short-term borrowings [Abstract] |  |  |
Balance at year-end | $ 143,386 | $ 143,775 | $ 160,696
Average during the year | 154,383 | 123,337 | 146,135
Maximum month end balance | $ 176,840 | $ 146,410 | $ 170,350
Weighted average rate during the year | 0.17% | 0.33% | 0.16%
Weighted average rate at year-end | 0.20% | 0.40% | 0.38%
Other Short-Term Borrowings [Member] |  |  |
Short-term borrowings [Abstract] |  |  |
Balance at year-end | $ 25,000 | $ 446,500 | $ 631,000
Average during the year | 183,699 | 403,453 | 514,662
Maximum month end balance | $ 366,500 | $ 576,000 | $ 653,000
Weighted average rate during the year | 1.55% | 1.85% | 1.56%
Weighted average rate at year-end | 1.99% | 1.73% | 1.82%

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