Loans (Non-Accrual Loans, Segregated by Class of Loans) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 53,713	$ 61,449
Financing Receivable, Nonaccrual, No Allowance	27,202	21,911
Commercial Portfolio Segment [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	22,582	19,849
Financing Receivable, Nonaccrual, No Allowance	4,701	4,479
Commercial and Industrial Total Energy Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	14,433	23,168
Financing Receivable, Nonaccrual, No Allowance	8,533	639
Paycheck Protection Program [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	0	0
Financing Receivable, Nonaccrual, No Allowance	0	0
Commercial Real Estate, Buildings, Land and Other [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	15,297	15,737
Financing Receivable, Nonaccrual, No Allowance	13,817	14,116
Construction Loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	948	1,684
Financing Receivable, Nonaccrual, No Allowance	0	1,684
Total consumer real estate loans [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	440	993
Financing Receivable, Nonaccrual, No Allowance	138	993
Consumer Loan [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	13	18
Financing Receivable, Nonaccrual, No Allowance	$ 13	$ 0