Fair Values of Assets and Liabilities - Quantitative Inputs and Assumptions Used in Level 3 Fair Value Measurements (Detail) - USD ($)	12 Months Ended
	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