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Allowance for Credit Losses and Credit Quality of Loans (Details) - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Sep. 30, 2021 | Dec. 31, 2020 | Jun. 30, 2021 | Sep. 30, 2020 | Jun. 30, 2020 | Dec. 31, 2019
Allowance for Credit Losses [Abstract] |  |  |  |  |  |
Allowance for credit losses | $ 93,000 | $ 110,000 | $ 98,500 | $ 114,500 | $ 113,500 | $ 75,999
Percentage of allowance of credit losses | 1.23% | 1.47% |  |  |  |
Retained earnings | $ 831,017 | $ 749,056 |  |  |  |
Loans purchased with credit deterioration | 0 | 0 |  |  |  |
Allowance for credit losses on loans purchased | 4,600 | 3,600 |  |  |  |
Accrued Interest Receivable [Member] |  |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |  |
Allowance for credit losses | 0 | 600 |  |  |  |
AIR on loans | $ 20,400 | 23,700 |  |  |  |
Write-off of uncollectible interest period | 120 days |  |  |  |  |
COVID-19 [Member] |  |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |  |
Loans in modification programs related to COVID-19 | $ 2,000 |  |  |  |  |
ASU 2016-13 [Member] | Loans [Member] |  |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |  |
Allowance for credit losses |  |  |  |  |  | 3,000
Retained earnings |  |  |  |  |  | (2,300)
Deferred tax asset |  |  |  |  |  | 700
Consumer Loans [Member] |  |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |  |
Allowance for credit losses | 41,071 | 37,803 | 34,881 | 38,562 | 40,094 | 32,122
Amount of loans purchased | 60,300 | $ 51,900 |  |  |  |
Discount on loans purchased |  | 1.00% |  |  |  |
Residential [Member] |  |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |  |
Allowance for credit losses | 18,751 | $ 21,255 | $ 19,428 | $ 24,192 | $ 23,020 | $ 16,721
Amount of loans purchased | $ 52,400 |  |  |  |  |
Premium on loans purchased | 2.00% |  |  |  |  |

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- Definition The write-off period of uncollectible interest of delinquent loans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Amount of financing receivables modified related to COVID-19. + References No definition available. + Details
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- Definition Amount of loans purchased with credit deterioration during the period. + References No definition available. + Details
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- Definition The premium percentage on loans purchased. + References No definition available. + Details
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- Definition Percentage of allowance for credit loss to total financing receivable outstanding. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph (a) -Subparagraph (1) + Details
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- Definition Reserve for loans impairments recorded after acquisition as a result of current information and events which result in it being probable that estimated cash flows will be less than previously expected or because actual cash flows are less than cash flows previously expected. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 15 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=123409700&loc=d3e13503-111538 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=121614798&loc=d3e15032-111544 + Details
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