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Allowance for Credit Losses - Additional Information (Detail) - USD ($) $ in Thousands |  |  | 3 Months Ended |
--- | --- | --- | --- | ---
Jan. 01, 2020 | Dec. 31, 2019 | Mar. 31, 2021 | Mar. 31, 2020 | Dec. 31, 2020
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Reserve for concentration risk |  |  | $ 5,435 |  |
Reserves on individually evaluated loans |  |  | 471 |  |
Allowance for credit loss |  | $ 30,616 | 85,941 | $ 57,911 | $ 91,847
Cumulative effect adjustment, decrease in retained earnings |  | 906,570 | 942,539 | 866,426 | 925,114
Threshold for loan analysis |  |  | 1,000 |  |
ASU 2016-13 |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Allowance for credit loss | $ 18,913 |  |  |  |
Reclassification of financing receivable | $ 481 |  |  |  |
Retained Earnings |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Cumulative effect adjustment, decrease in retained earnings |  | 367,794 | 408,211 | 356,935 | $ 381,999
Impact of CECL Adoption |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Allowance for credit loss |  | 18,913 |  |  |
Tax portion of cumulative effect adjustment |  | 5,449 |  |  |
Cumulative effect adjustment, decrease in retained earnings |  | (12,983) |  |  |
Impact of CECL Adoption | Retained Earnings |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Cumulative effect adjustment, decrease in retained earnings |  | $ (12,983) |  |  |
Financial Asset Originated |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Interest lost on nonaccrual loans |  |  | 536 | 431 |
Interest income on nonaccrual loans |  |  | $ 17 | $ 47 |

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- Definition Financing Receivable, Allowance For Credit Losses, Individually Evaluated For Impairment, Increase (Decrease) + References No definition available. + Details
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- Definition Financing Receivable, Allowance For Credit Losses, Reserve For Concentration Risk, Increase (Decrease) + References No definition available. + Details
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- Definition Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524 Reference 2: 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=118955202&loc=SL82895884-210446 Reference 3: 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=119407570&loc=SL82919249-210447 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(7)(d)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 5: 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=119407570&loc=SL82919249-210447 + Details
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