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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
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Dec. 31, 2022 | Dec. 31, 2021
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Assets, Fair Value Disclosure | $ 869,373,000 | $ 1,114,587,000
Other Assets, Fair Value Disclosure | 68,429,000 | 41,786,000
Other investments | 26,414,000 | 12,838,000
Fair Value, Inputs, Level 2 [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Assets, Fair Value Disclosure | 850,512,000 | 1,098,436,000
Other Assets, Fair Value Disclosure | 50,738,000 | 26,805,000
Other investments | 25,244,000 | 11,668,000
Fair Value, Inputs, Level 3 [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Assets, Fair Value Disclosure | 18,861,000 | 16,151,000
Other Assets, Fair Value Disclosure | $ 17,691,000 | $ 14,981,000
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 | $ 1,170,000 | $ 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 | $ 598,000
Fair Value Measurements, Valuation Processes, Description | Gas Reserve Study | 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 | 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 | 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 | Oil per BBL/d
Fair Value, Nonrecurring [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |
Assets, Fair Value Disclosure | $ 35,329,000 | $ 55,514,000
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 | 23,693,000 | 43,267,000
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 | 11,636,000 | 12,247,000
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 | 2.00
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 | $ 50.00
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% | 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 | $ 2.00
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 | $ 50.00

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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 -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258 + Details
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