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Investment Securities - Narrative (Details) $ in Thousands | Mar. 31, 2021 USD ($) instrument | Dec. 31, 2020 USD ($)
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Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |
Accrued interest on investment securities | $ 20,600 |
Allowance for credit losses | 245 | $ 0
Gross unrealized losses | 19,186 | 349
Carrying value of securities pledged as collateral | 999,200 | 890,000
Securities sold under repurchase agreements | 178,200 | 167,300
State and municipal |  |
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |
Allowance for credit losses | 245 | 0
Gross unrealized losses | $ 2,654 | 246
Number of securities in unrealized loss positions | instrument | 108 |
U.S. Government-sponsored mortgage-backed securities |  |
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |
Allowance for credit losses | $ 0 | 0
Gross unrealized losses | $ 16,347 | 103
Number of securities in unrealized loss positions | instrument | 55 |
U.S. Government-sponsored agency securities |  |
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |
Allowance for credit losses | $ 0 | 0
Gross unrealized losses | $ 163 | 0
Number of securities in unrealized loss positions | instrument | 2 |
Corporate obligations |  |
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |
Gross unrealized losses | $ 22 | $ 0
Number of securities in unrealized loss positions | instrument | 1 |

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- Definition Amount, before tax, of unrealized loss 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 (c) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details
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- Definition Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922888-210455 + Details
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