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Securities Securities (Reconciliation of amortized cost of held to maturity securities) (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | $ 805,529 | $ 724,512
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 21,311 | 28,007
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | (6,410) | (342)
Debt Securities, Held-to-maturity, Allowance for Credit Loss | 0 | 0
Debt Securities, Held-to-maturity, Fair Value | 820,430 | 752,177
Small Business Administration Pooled Securities [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 26,518 | 26,917
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 717 | 1,445
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | 0 | 0
Debt Securities, Held-to-maturity, Allowance for Credit Loss | 0 | 0
Debt Securities, Held-to-maturity, Fair Value | 27,235 | 28,362
Trust Preferred Securities Subject to Mandatory Redemption [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 1,500 | 1,500
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 8 | 0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | 0 | (2)
Debt Securities, Held-to-maturity, Allowance for Credit Loss | 0 | 0
Debt Securities, Held-to-maturity, Fair Value | 1,508 | 1,498
Collateralized Debt Obligations [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 355,686 | 335,993
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 7,474 | 8,466
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | (2,158) | (340)
Debt Securities, Held-to-maturity, Allowance for Credit Loss | 0 | 0
Debt Securities, Held-to-maturity, Fair Value | 361,002 | 344,119
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 417,811 | 356,085
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 13,069 | 18,036
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | (4,252) | 0
Debt Securities, Held-to-maturity, Allowance for Credit Loss | 0 | 0
Debt Securities, Held-to-maturity, Fair Value | 426,628 | 374,121
US Treasury Securities [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 4,014 | 4,017
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 43 | 60
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | 0 | 0
Debt Securities, Held-to-maturity, Allowance for Credit Loss | 0 | 0
Debt Securities, Held-to-maturity, Fair Value | $ 4,057 | $ 4,077

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- Definition Amount of allowance for credit loss for debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aaa) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121599878&loc=SL82895884-210446 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447 + Details
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