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Investment Securities - Amortized Cost of Investment Securities Held to Maturity (Details) - USD ($) $ in Thousands | Jun. 30, 2022 | Dec. 31, 2021
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Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | $ 2,333,924 | $ 2,180,047
Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 162,632 |
Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 163,091 |
Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 185,950 |
Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 134,000 |
A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 132,754 |
A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 10,165 |
A3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 10,112 |
Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 1,535,220 |
State and municipal |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 1,117,526 | $ 1,057,301
State and municipal | Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 102,051 |
State and municipal | Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 163,091 |
State and municipal | Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 185,950 |
State and municipal | Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 134,000 |
State and municipal | A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 132,754 |
State and municipal | A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 10,165 |
State and municipal | A3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 10,112 |
State and municipal | Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 379,403 |
Other |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 1,216,398 |
Other | Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 60,581 |
Other | Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 0 |
Other | Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 0 |
Other | Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 0 |
Other | A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 0 |
Other | A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 0 |
Other | A3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | 0 |
Other | Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Amortized Cost | $ 1,155,817 |

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- Definition Amount excluding accrued interest, before allowance for credit loss, of investment in 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 5 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919230-210447 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 3B -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL120267963-210447 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446 + Details
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