Loans (Investment in Loans Related to Allowance for Loan Loss by Portfolio Segment Disaggregated Based on Impairment Methodology) (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 17,154,969	$ 16,336,397
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,674,798	5,364,954
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	925,729	1,077,792
Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	34,852	428,882
Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6,706,078	6,272,339
Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,477,247	1,304,271
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,843,539	1,410,790
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	492,726	477,369
Specific Valuation Allowances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	12,181	16,452
Specific Valuation Allowances [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	6,082	10,536
Specific Valuation Allowances [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	4,383	5,480
Specific Valuation Allowances [Member] \| Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	0	0
Specific Valuation Allowances [Member] \| Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	1,716	200
Specific Valuation Allowances [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	0	200
Specific Valuation Allowances [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	0	36
Specific Valuation Allowances [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of allowance for loan losses	0	0
Loans Individually Evaluated for Impairment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	52,576	66,837
Loans Individually Evaluated for Impairment [Member] \| Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	18,980	24,523
Loans Individually Evaluated for Impairment [Member] \| Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	15,058	16,393
Loans Individually Evaluated for Impairment [Member] \| Paycheck Protection Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0	0
Loans Individually Evaluated for Impairment [Member] \| Commercial Real Estate, Buildings, Land and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	17,711	24,670
Loans Individually Evaluated for Impairment [Member] \| Construction Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0	948
Loans Individually Evaluated for Impairment [Member] \| Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	827	303
Loans Individually Evaluated for Impairment [Member] \| Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 0	$ 0