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Investments (Unrealized Gross Losses and Estimated Fair values of Investment Securities by Length of Time that Individual Securities in Each Category in Continuous Loss Position) (Details) $ in Thousands | Dec. 31, 2020 USD ($) security | Dec. 31, 2019 USD ($) security
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Debt Securities, Available-for-sale [Line Items] |  |
Number of Holdings, AFS Investments in Unrealized Loss Positions | security | 30 | 105
AFS Fair Value - Less Than 12 Months Loss Position | $ 107,635 | $ 259,972
AFS Unrealized Losses - Less Than 12 Months Loss Position | (916) | (2,911)
AFS Fair Value - 12 Months or More Loss Position | 980 | 132,247
AFS Unrealized Losses - 12 Months or More Loss Position | (6) | (2,500)
AFS Fair Value - Loss Position | 108,615 | 392,219
AFS Unrealized Losses | $ (922) | $ (5,411)
Obligations of states and political subdivisions |  |
Debt Securities, Available-for-sale [Line Items] |  |
Number of Holdings, AFS Investments in Unrealized Loss Positions | security | 1 | 11
AFS Fair Value - Less Than 12 Months Loss Position | $ 2,404 | $ 30,459
AFS Unrealized Losses - Less Than 12 Months Loss Position | (115) | (328)
AFS Fair Value - 12 Months or More Loss Position | 0 | 0
AFS Unrealized Losses - 12 Months or More Loss Position | 0 | 0
AFS Fair Value - Loss Position | 2,404 | 30,459
AFS Unrealized Losses | $ (115) | $ (328)
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises |  |
Debt Securities, Available-for-sale [Line Items] |  |
Number of Holdings, AFS Investments in Unrealized Loss Positions | security | 15 | 59
AFS Fair Value - Less Than 12 Months Loss Position | $ 61,222 | $ 162,964
AFS Unrealized Losses - Less Than 12 Months Loss Position | (568) | (1,850)
AFS Fair Value - 12 Months or More Loss Position | 980 | 63,633
AFS Unrealized Losses - 12 Months or More Loss Position | (6) | (755)
AFS Fair Value - Loss Position | 62,202 | 226,597
AFS Unrealized Losses | $ (574) | $ (2,605)
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises |  |
Debt Securities, Available-for-sale [Line Items] |  |
Number of Holdings, AFS Investments in Unrealized Loss Positions | security | 9 | 35
AFS Fair Value - Less Than 12 Months Loss Position | $ 39,107 | $ 66,549
AFS Unrealized Losses - Less Than 12 Months Loss Position | (135) | (733)
AFS Fair Value - 12 Months or More Loss Position | 0 | 68,614
AFS Unrealized Losses - 12 Months or More Loss Position | 0 | (1,745)
AFS Fair Value - Loss Position | 39,107 | 135,163
AFS Unrealized Losses | $ (135) | $ (2,478)
Subordinated corporate bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Number of Holdings, AFS Investments in Unrealized Loss Positions | security | 5 |
AFS Fair Value - Less Than 12 Months Loss Position | $ 4,902 |
AFS Unrealized Losses - Less Than 12 Months Loss Position | (98) |
AFS Fair Value - 12 Months or More Loss Position | 0 |
AFS Unrealized Losses - 12 Months or More Loss Position | 0 |
AFS Fair Value - Loss Position | 4,902 |
AFS Unrealized Losses | $ (98) |

X
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