Allowance for Credit Losses - Schedule Of Credit Losses Related To Accrued Interest Receivables and Written Off (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Accrued Interest Receivables and Written off Status [Line Items]
Accrued Interest Receivable	$ 56,124,000	$ 56,124,000	$ 48,130,000
Accrued Interest Receivables Written Off by Reversing Interest Income	245	391
Construction [Member]
Accrued Interest Receivables and Written off Status [Line Items]
Accrued Interest Receivable	6,825,000	6,825,000
Accrued Interest Receivables Written Off by Reversing Interest Income	0	0
Commercial Real Estate [Member] | Owner-Occupied [Member]
Accrued Interest Receivables and Written off Status [Line Items]
Accrued Interest Receivable	4,910,000	4,910,000
Accrued Interest Receivables Written Off by Reversing Interest Income	83	100
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Accrued Interest Receivables and Written off Status [Line Items]
Accrued Interest Receivable	18,107,000	18,107,000
Accrued Interest Receivables Written Off by Reversing Interest Income	38	45
Other Commercial [Member]
Accrued Interest Receivables and Written off Status [Line Items]
Accrued Interest Receivable	9,350,000	9,350,000
Accrued Interest Receivables Written Off by Reversing Interest Income	33	45
Residential Real Estate [Member]
Accrued Interest Receivables and Written off Status [Line Items]
Accrued Interest Receivable	14,085,000	14,085,000
Accrued Interest Receivables Written Off by Reversing Interest Income	64	134
Consumer [Member] | Bankcard [Member]
Accrued Interest Receivables and Written off Status [Line Items]
Accrued Interest Receivable	0	0
Accrued Interest Receivables Written Off by Reversing Interest Income	0	0
Consumer [Member] | Other Consumer [Member]
Accrued Interest Receivables and Written off Status [Line Items]
Accrued Interest Receivable	2,847,000	2,847,000
Accrued Interest Receivables Written Off by Reversing Interest Income	$ 27	$ 67