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Fair Values of Assets and Liabilities - Quantitative Inputs and Assumptions Used in Level 3 Fair Value Measurements (Detail) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Assets, Fair Value Disclosure | $ 1,161,482,000 | $ 869,373,000
Other Assets, Fair Value Disclosure | 59,805,000 | 68,429,000
Other investments | 50,871,000 | 26,414,000
Fair Value, Inputs, Level 2 [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Assets, Fair Value Disclosure | 1,128,163,000 | 850,512,000
Other Assets, Fair Value Disclosure | 32,668,000 | 50,738,000
Other investments | 44,689,000 | 25,244,000
Fair Value, Inputs, Level 3 [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Assets, Fair Value Disclosure | 33,319,000 | 18,861,000
Other Assets, Fair Value Disclosure | $ 27,137,000 | $ 17,691,000
Other Assets [Member] | Par Value [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Fair Value Measurements, Valuation Processes, Description | Par Value | Par Value
Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Other investments | $ 6,182,000 | $ 1,170,000
Equity Securities [Member] | Par Value [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Fair Value Measurements, Valuation Processes, Description | Carrying Value | Carrying Value
Impaired Loans [Member] | Reserve [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Assets, Fair Value Disclosure |  | $ 363,000
Fair Value Measurements, Valuation Processes, Description |  | Gas Reserve study
Impaired Loans [Member] | Discount Rates [Member] | Reserve [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Fair Value Measurements, Valuation Processes, Description |  | Discount rate
Impaired Loans [Member] | Gas Per Million Cubic Feet [Member] | Reserve [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Fair Value Measurements, Valuation Processes, Description |  | Gas per MMBTU
Impaired Loans [Member] | Oil Per Barrels Per Day [Member] | Reserve [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Fair Value Measurements, Valuation Processes, Description |  | Oil per BBL/d
Fair Value, Nonrecurring [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Assets, Fair Value Disclosure | $ 35,532,000 | $ 35,329,000
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Assets, Fair Value Disclosure | 25,824,000 | 23,693,000
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Assets, Fair Value Disclosure | $ 9,708,000 | 11,636,000
Minimum [Member] | Impaired Loans [Member] | Reserve [Member] | Gas Per Million Cubic Feet [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Fair Value Weighted Average Inputs Price |  | 3.00
Minimum [Member] | Impaired Loans [Member] | Reserve [Member] | Oil Per Barrels Per Day [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Fair Value Weighted Average Inputs Price |  | $ 80.00
Weighted Average [Member] | Impaired Loans [Member] | Reserve [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Fair Value Input, Discount Rate |  | 10.00%
Maximum [Member] | Impaired Loans [Member] | Reserve [Member] | Gas Per Million Cubic Feet [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Fair Value Weighted Average Inputs Price |  | $ 3.00
Maximum [Member] | Impaired Loans [Member] | Reserve [Member] | Oil Per Barrels Per Day [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Fair Value Weighted Average Inputs Price |  | $ 80.00

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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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