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Investments (Summary of Amortized Costs and Estimated Fair Values of Available-For-Sale Securities) (Details) - USD ($) $ in Thousands | Dec. 31, 2021 | Dec. 31, 2020
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Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost | $ 1,508,981 | $ 1,078,474
Unrealized Gains | 16,235 | 38,261
Unrealized Losses | (17,730) | (922)
Fair Value | 1,507,486 | 1,115,813
Obligations of states and political subdivisions |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost | 112,086 | 119,608
Unrealized Gains | 5,392 | 7,627
Unrealized Losses | 0 | (115)
Fair Value | 117,478 | 127,120
Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost | 1,003,869 | 547,396
Unrealized Gains | 7,856 | 19,796
Unrealized Losses | (11,468) | (574)
Fair Value | 1,000,257 | 566,618
Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost | 361,781 | 399,937
Unrealized Gains | 2,835 | 10,652
Unrealized Losses | (5,767) | (135)
Fair Value | 358,849 | 410,454
Subordinated corporate bonds |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost | 22,660 | 11,533
Unrealized Gains | 152 | 186
Unrealized Losses | (254) | (98)
Fair Value | 22,558 | $ 11,621
US Government-sponsored Enterprises Debt Securities |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost | 8,585 |
Unrealized Gains | 0 |
Unrealized Losses | (241) |
Fair Value | $ 8,344 |

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- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563 + Details
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