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Securities - Summary of Gross Unrealized Losses and Fair Values, Aggregated by Investment Category and Length of Individual Securities Continuous Unrealized Loss Position Available-for-sale (Details) $ in Thousands | Sep. 30, 2020 USD ($) Security | Dec. 31, 2019 USD ($) Security
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Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security | 41 | 99
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | $ 258,799 | $ 343,722
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses | (1,735) | (2,377)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value | 19,703 | 257,869
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses | (626) | (2,328)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 278,502 | 601,591
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses | $ (2,361) | $ (4,705)
U.S. Government Agencies |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security | 7 | 8
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | $ 50,779 | $ 49,318
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses | (357) | (662)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |  | 20,283
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses |  | (92)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 50,779 | 69,601
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses | $ (357) | $ (754)
Obligations of States, Municipalities, and Political Subdivisions |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security | 1 | 7
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | $ 126 | $ 13,309
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses |  | (45)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |  | 1,419
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses |  | (4)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | $ 126 | 14,728
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses |  | $ (49)
Agency, Residential Mortgage-Backed Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security | 11 | 50
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | $ 116,877 | $ 132,703
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses | (349) | (666)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value | 503 | 193,363
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses | (6) | (1,688)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 117,380 | 326,066
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses | $ (355) | $ (2,354)
Non-Agency, Residential Mortgage-Backed Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security |  | 9
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value |  | $ 36,902
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses |  | (206)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |  | 10,126
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses |  | (66)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value |  | 47,028
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses |  | $ (272)
Agency, Commercial Mortgage-Backed Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security | 7 | 13
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | $ 59,474 | $ 67,649
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses | (513) | (563)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |  | 32,678
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses |  | (478)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 59,474 | 100,327
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses | $ (513) | $ (1,041)
Corporate Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security | 7 | 4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | $ 12,304 | $ 6,103
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses | (215) | (37)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 12,304 | 6,103
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses | $ (215) | $ (37)
Asset-Backed Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Securities | Security | 8 | 8
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | $ 19,239 | $ 37,738
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses | (301) | (198)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value | 19,200 |
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses | (620) |
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 38,439 | 37,738
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Unrealized Losses | $ (921) | $ (198)

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