Loans and Leases and the Allowance for Credit Losses - Summary of Loan grades applied various classes of Commercial and Real Estate Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	$ 15,279,000		$ 15,279,000		$ 18,423,000
Year two	15,890,000		15,890,000		21,683,000
Year three	18,767,000		18,767,000		15,025,000
Year four	12,542,000		12,542,000		10,555,000
Year five	8,957,000		8,957,000		10,062,000
Prior	30,732,000		30,732,000		27,464,000
Total	135,920,000		135,920,000		134,068,000
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	12,000		19,000
Year two	20,000		55,000
Year three	35,000		76,000
Year four	10,000		42,000
Year five	7,000		31,000
Prior	39,000		127,000
Total	154,000	$ 122,000	497,000	$ 379,000
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	7,020,000		7,020,000		9,010,000
Year two	7,474,000		7,474,000		8,434,000
Year three	6,992,000		6,992,000		5,133,000
Year four	4,089,000		4,089,000		2,465,000
Year five	1,991,000		1,991,000		2,332,000
Prior	6,355,000		6,355,000		5,474,000
Revolving Loans	26,958,000		26,958,000		24,048,000
Revolving Loans Converted to Term Loans	133,000		133,000		114,000
Total	61,012,000		61,012,000		57,010,000
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	3,000		4,000
Year two	10,000		24,000
Year three	25,000		44,000
Year four	4,000		19,000
Year five	2,000		12,000
Prior	8,000		22,000
Revolving Loans	12,000		95,000
Revolving Loans Converted to Term Loans	0		0
Total	64,000		220,000
Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	6,885,000		6,885,000		8,689,000
Year two	7,018,000		7,018,000		8,087,000
Year three	6,491,000		6,491,000		4,800,000
Year four	3,825,000		3,825,000		2,248,000
Year five	1,802,000		1,802,000		2,169,000
Prior	5,440,000		5,440,000		4,843,000
Revolving Loans	25,290,000		25,290,000		22,345,000
Revolving Loans Converted to Term Loans	78,000		78,000		70,000
Total	56,829,000		56,829,000		53,251,000
Commercial and industrial | Criticized accrual
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	128,000		128,000		292,000
Year two	400,000		400,000		279,000
Year three	419,000		419,000		277,000
Year four	218,000		218,000		142,000
Year five	122,000		122,000		127,000
Prior	641,000		641,000		481,000
Revolving Loans	1,408,000		1,408,000		1,460,000
Revolving Loans Converted to Term Loans	37,000		37,000		31,000
Total	3,373,000		3,373,000		3,089,000
Commercial and industrial | Criticized nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	7,000		7,000		29,000
Year two	56,000		56,000		68,000
Year three	82,000		82,000		56,000
Year four	46,000		46,000		75,000
Year five	67,000		67,000		36,000
Prior	274,000		274,000		150,000
Revolving Loans	260,000		260,000		243,000
Revolving Loans Converted to Term Loans	18,000		18,000		13,000
Total	810,000		810,000		670,000
Commercial Real Estate
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Total	24,000	$ 52,000	92,000	$ 180,000
Commercial Real Estate | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1,008,000		1,008,000		2,275,000
Year two	1,957,000		1,957,000		2,679,000
Year three	2,099,000		2,099,000		1,835,000
Year four	1,545,000		1,545,000		2,580,000
Year five	2,545,000		2,545,000		4,118,000
Prior	12,809,000		12,809,000		11,340,000
Revolving Loans	408,000		408,000		450,000
Revolving Loans Converted to Term Loans	0		0		0
Total	22,371,000		22,371,000		25,277,000
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0		0
Year two	0		4,000
Year three	0		0
Year four	0		0
Year five	0		5,000
Prior	24,000		67,000
Revolving Loans	0		0
Revolving Loans Converted to Term Loans	0		0
Total	24,000		76,000
Commercial Real Estate | Commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1,003,000		1,003,000		2,048,000
Year two	1,648,000		1,648,000		1,742,000
Year three	1,296,000		1,296,000		1,367,000
Year four	1,190,000		1,190,000		2,011,000
Year five	1,861,000		1,861,000		3,059,000
Prior	10,308,000		10,308,000		8,491,000
Revolving Loans	383,000		383,000		440,000
Revolving Loans Converted to Term Loans	0		0		0
Total	17,689,000		17,689,000		19,158,000
Commercial Real Estate | Commercial | Criticized accrual
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	5,000		5,000		227,000
Year two	308,000		308,000		891,000
Year three	752,000		752,000		465,000
Year four	323,000		323,000		456,000
Year five	648,000		648,000		966,000
Prior	2,044,000		2,044,000		2,238,000
Revolving Loans	24,000		24,000		7,000
Revolving Loans Converted to Term Loans	0		0		0
Total	4,104,000		4,104,000		5,250,000
Commercial Real Estate | Commercial | Criticized nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0		0		0
Year two	1,000		1,000		46,000
Year three	51,000		51,000		3,000
Year four	32,000		32,000		113,000
Year five	36,000		36,000		93,000
Prior	457,000		457,000		611,000
Revolving Loans	1,000		1,000		3,000
Revolving Loans Converted to Term Loans	0		0		0
Total	578,000		578,000		869,000
Commercial Real Estate | Residential builder and developer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	342,000		342,000		531,000
Year two	366,000		366,000		270,000
Year three	124,000		124,000		74,000
Year four	26,000		26,000		6,000
Year five	4,000		4,000		61,000
Prior	28,000		28,000		12,000
Revolving Loans	102,000		102,000		119,000
Revolving Loans Converted to Term Loans	0		0		0
Total	992,000		992,000		1,073,000
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
Prior	0		2,000
Revolving Loans	0		0
Revolving Loans Converted to Term Loans	0		0
Total	0		2,000
Commercial Real Estate | Residential builder and developer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	333,000		333,000		530,000
Year two	323,000		323,000		252,000
Year three	78,000		78,000		41,000
Year four	19,000		19,000		6,000
Year five	4,000		4,000		2,000
Prior	11,000		11,000		12,000
Revolving Loans	101,000		101,000		116,000
Revolving Loans Converted to Term Loans	0		0		0
Total	869,000		869,000		959,000
Commercial Real Estate | Residential builder and developer | Criticized accrual
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	9,000		9,000		1,000
Year two	43,000		43,000		18,000
Year three	46,000		46,000		30,000
Year four	6,000		6,000		0
Year five	0		0		59,000
Prior	16,000		16,000		0
Revolving Loans	1,000		1,000		3,000
Revolving Loans Converted to Term Loans	0		0		0
Total	121,000		121,000		111,000
Commercial Real Estate | Residential builder and developer | Criticized nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0		0		0
Year two	0		0		0
Year three	0		0		3,000
Year four	1,000		1,000		0
Year five	0		0		0
Prior	1,000		1,000		0
Revolving Loans	0		0		0
Revolving Loans Converted to Term Loans	0		0		0
Total	2,000		2,000		3,000
Commercial Real Estate | Other commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	87,000		87,000		866,000
Year two	1,377,000		1,377,000		1,771,000
Year three	1,891,000		1,891,000		1,051,000
Year four	746,000		746,000		1,110,000
Year five	521,000		521,000		1,261,000
Prior	644,000		644,000		562,000
Revolving Loans	54,000		54,000		32,000
Revolving Loans Converted to Term Loans	0		0		0
Total	5,320,000		5,320,000		6,653,000
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0		0
Year two	0		0
Year three	0		2,000
Year four	0		0
Year five	0		0
Prior	0		10,000
Revolving Loans	0		2,000
Revolving Loans Converted to Term Loans	0		0
Total	0		14,000
Commercial Real Estate | Other commercial construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	68,000		68,000		813,000
Year two	1,290,000		1,290,000		1,366,000
Year three	1,213,000		1,213,000		651,000
Year four	283,000		283,000		373,000
Year five	161,000		161,000		646,000
Prior	339,000		339,000		187,000
Revolving Loans	46,000		46,000		30,000
Revolving Loans Converted to Term Loans	0		0		0
Total	3,400,000		3,400,000		4,066,000
Commercial Real Estate | Other commercial construction | Criticized accrual
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	19,000		19,000		53,000
Year two	87,000		87,000		391,000
Year three	673,000		673,000		390,000
Year four	454,000		454,000		691,000
Year five	311,000		311,000		565,000
Prior	284,000		284,000		326,000
Revolving Loans	8,000		8,000		0
Revolving Loans Converted to Term Loans	0		0		0
Total	1,836,000		1,836,000		2,416,000
Commercial Real Estate | Other commercial construction | Criticized nonaccrual
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0		0		0
Year two	0		0		14,000
Year three	5,000		5,000		10,000
Year four	9,000		9,000		46,000
Year five	49,000		49,000		50,000
Prior	21,000		21,000		49,000
Revolving Loans	0		0		2,000
Revolving Loans Converted to Term Loans	0		0		0
Total	$ 84,000		$ 84,000		$ 171,000