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Securities - Summary of Amortized Cost and Fair Values of Securities Available-for-sale (Details) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
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Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Amortized Cost | $ 1,433,152 | $ 1,418,445
Available-for-sale Securities, Gross Unrealized Gains | 13,354 | 29,834
Available-for-sale Securities, Gross Unrealized Losses | (18,901) | (1,049)
Available-for-sale Securities, Fair Value | 1,427,605 | 1,447,230
U.S. Treasury Notes |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Amortized Cost | 8,487 | 23,468
Available-for-sale Securities, Gross Unrealized Gains | 91 | 344
Available-for-sale Securities, Gross Unrealized Losses | 0 | 0
Available-for-sale Securities, Fair Value | 8,578 | 23,812
U.S. Government Agencies |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Amortized Cost | 124,244 | 113,088
Available-for-sale Securities, Gross Unrealized Gains | 885 | 600
Available-for-sale Securities, Gross Unrealized Losses | (1,865) | (137)
Available-for-sale Securities, Fair Value | 123,264 | 113,551
Obligations of States, Municipalities, and Political Subdivisions |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Amortized Cost | 101,499 | 135,513
Available-for-sale Securities, Gross Unrealized Gains | 3,725 | 6,991
Available-for-sale Securities, Gross Unrealized Losses | (164) | (85)
Available-for-sale Securities, Fair Value | 105,060 | 142,419
Agency, Residential Mortgage-Backed Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Amortized Cost | 794,856 | 764,951
Available-for-sale Securities, Gross Unrealized Gains | 3,303 | 13,645
Available-for-sale Securities, Gross Unrealized Losses | (12,986) | (205)
Available-for-sale Securities, Fair Value | 785,173 | 778,391
Non-Agency, Residential Mortgage-Backed Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Amortized Cost | 64,645 | 32,654
Available-for-sale Securities, Gross Unrealized Gains | 86 | 332
Available-for-sale Securities, Gross Unrealized Losses | (722) | (5)
Available-for-sale Securities, Fair Value | 64,009 | 32,981
Agency, Commercial Mortgage-Backed Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Amortized Cost | 237,376 | 244,496
Available-for-sale Securities, Gross Unrealized Gains | 3,179 | 6,046
Available-for-sale Securities, Gross Unrealized Losses | (3,146) | (390)
Available-for-sale Securities, Fair Value | 237,409 | 250,152
Corporate Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Amortized Cost | 64,842 | 59,020
Available-for-sale Securities, Gross Unrealized Gains | 2,002 | 1,850
Available-for-sale Securities, Gross Unrealized Losses | (17) | (102)
Available-for-sale Securities, Fair Value | 66,827 | 60,768
Asset-Backed Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Available-for-sale Securities, Amortized Cost | 37,203 | 45,255
Available-for-sale Securities, Gross Unrealized Gains | 83 | 26
Available-for-sale Securities, Gross Unrealized Losses | (1) | (125)
Available-for-sale Securities, Fair Value | $ 37,285 | $ 45,156

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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=121645371&loc=d3e27161-111563 + Details
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