Loans and the Allowance for Credit Losses - Summary of Amortized Cost Basis Loan Balances by Year of Origination and Credit Quality Indicator (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ (11,315,873)	$ (10,702,728)
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(10,612)	(11,222)
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(6,916)	(6,621)
90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(26,728)	(30,986)
Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	11,528	10,798
Amortized Cost Basis by Origination Year 2022	1,536	1,535
Amortized Cost Basis by Origination Year 2021	1,864	1,885
Amortized Cost Basis by Origination Year 2020	2,743	1,984
Amortized Cost Basis by Origination Year 2019	2,354	1,467
Amortized Cost Basis by Origination Year, Prior to 2019	(28,148)	(29,251)
Revolving Loans	665,468	646,706
Revolving Loans Converted to Term	1,545	1,439
Total loans	(715,186)	(695,065)
Home Equity [Member] | Current [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	11,528	10,718
Amortized Cost Basis by Origination Year 2022	947	1,459
Amortized Cost Basis by Origination Year 2021	1,581	1,133
Amortized Cost Basis by Origination Year 2020	1,709	1,774
Amortized Cost Basis by Origination Year 2019	1,912	1,088
Amortized Cost Basis by Origination Year, Prior to 2019	(23,294)	(25,203)
Revolving Loans	663,347	644,430
Revolving Loans Converted to Term	1,117	957
Total loans	(705,435)	(686,762)
Home Equity [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023		80
Amortized Cost Basis by Origination Year 2022	230	61
Amortized Cost Basis by Origination Year 2021	67	180
Amortized Cost Basis by Origination Year 2020	169	67
Amortized Cost Basis by Origination Year 2019	50	34
Amortized Cost Basis by Origination Year, Prior to 2019	(953)	(1,165)
Revolving Loans	2,121	2,260
Revolving Loans Converted to Term	9	38
Total loans	(3,599)	(3,885)
Home Equity [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2022	175	15
Amortized Cost Basis by Origination Year 2021	161
Amortized Cost Basis by Origination Year 2020	326	50
Amortized Cost Basis by Origination Year 2019	109	88
Amortized Cost Basis by Origination Year, Prior to 2019	(438)	(458)
Revolving Loans Converted to Term		10
Total loans	(1,209)	(621)
Home Equity [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2022	184
Amortized Cost Basis by Origination Year 2021	55	572
Amortized Cost Basis by Origination Year 2020	539	93
Amortized Cost Basis by Origination Year 2019	283	257
Amortized Cost Basis by Origination Year, Prior to 2019	(3,463)	(2,425)
Revolving Loans		16
Revolving Loans Converted to Term	419	434
Total loans	(4,943)	(3,797)
Home Equity [Member] | Current-period gross charge-offs [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2022	139
Amortized Cost Basis by Origination Year 2021	54
Amortized Cost Basis by Origination Year 2020	1
Amortized Cost Basis by Origination Year 2019	29
Amortized Cost Basis by Origination Year, Prior to 2019	(441)	(310)
Revolving Loans	6
Revolving Loans Converted to Term		48
Total loans	(670)	(358)
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(6,387,183)	(6,061,344)
Commercial Real Estate [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(2,161)	(2,147)
Commercial Real Estate [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(1,279)	(1,241)
Commercial Real Estate [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(14,608)	(16,378)
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	213,154	541,659
Amortized Cost Basis by Origination Year 2022	481,504	557,370
Amortized Cost Basis by Origination Year 2021	464,469	211,845
Amortized Cost Basis by Origination Year 2020	188,572	97,510
Amortized Cost Basis by Origination Year 2019	88,393	52,254
Amortized Cost Basis by Origination Year, Prior to 2019	(482,544)	(489,164)
Revolving Loans Converted to Term	473,895	190,782
Total loans	(2,392,531)	(2,140,584)
Residential Real Estate [Member] | Current [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	212,958	541,659
Amortized Cost Basis by Origination Year 2022	481,377	556,928
Amortized Cost Basis by Origination Year 2021	464,248	211,496
Amortized Cost Basis by Origination Year 2020	188,572	97,160
Amortized Cost Basis by Origination Year 2019	88,126	52,135
Amortized Cost Basis by Origination Year, Prior to 2019	(475,232)	(478,977)
Revolving Loans Converted to Term	473,321	190,740
Total loans	(2,383,834)	(2,129,095)
Residential Real Estate [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year, Prior to 2019	(1,134)	(853)
Total loans	(1,134)	(853)
Residential Real Estate [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	196
Amortized Cost Basis by Origination Year 2022	127	442
Amortized Cost Basis by Origination Year 2021	34	349
Amortized Cost Basis by Origination Year 2020		65
Amortized Cost Basis by Origination Year 2019	52
Amortized Cost Basis by Origination Year, Prior to 2019	(2,004)	(2,680)
Revolving Loans Converted to Term	542
Total loans	(2,955)	(3,536)
Residential Real Estate [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2021	187
Amortized Cost Basis by Origination Year 2020		285
Amortized Cost Basis by Origination Year 2019	215	119
Amortized Cost Basis by Origination Year, Prior to 2019	(4,174)	(6,654)
Revolving Loans Converted to Term	32	42
Total loans	(4,608)	(7,100)
Residential Real Estate [Member] | Current-period gross charge-offs [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2019	5	6
Amortized Cost Basis by Origination Year, Prior to 2019	(273)	(494)
Total loans	(278)	(500)
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	73,581	86,164
Amortized Cost Basis by Origination Year 2022	65,477	37,561
Amortized Cost Basis by Origination Year 2021	25,836	25,722
Amortized Cost Basis by Origination Year 2020	16,222	25,773
Amortized Cost Basis by Origination Year 2019	13,942	8,617
Amortized Cost Basis by Origination Year, Prior to 2019	(14,236)	(16,690)
Revolving Loans	24,068	25,786
Revolving Loans Converted to Term		27
Total loans	(233,362)	(226,340)
Consumer [Member] | Current [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	72,886	84,817
Amortized Cost Basis by Origination Year 2022	63,086	36,123
Amortized Cost Basis by Origination Year 2021	24,744	25,071
Amortized Cost Basis by Origination Year 2020	15,868	25,535
Amortized Cost Basis by Origination Year 2019	13,851	8,488
Amortized Cost Basis by Origination Year, Prior to 2019	(13,989)	(16,337)
Revolving Loans	23,967	25,755
Revolving Loans Converted to Term		27
Total loans	(228,391)	(222,153)
Consumer [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	570	980
Amortized Cost Basis by Origination Year 2022	1,384	937
Amortized Cost Basis by Origination Year 2021	657	488
Amortized Cost Basis by Origination Year 2020	231	159
Amortized Cost Basis by Origination Year 2019	62	98
Amortized Cost Basis by Origination Year, Prior to 2019	(147)	(217)
Revolving Loans	101	31
Total loans	(3,152)	(2,910)
Consumer [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	42	184
Amortized Cost Basis by Origination Year 2022	556	293
Amortized Cost Basis by Origination Year 2021	329	94
Amortized Cost Basis by Origination Year 2020	49	47
Amortized Cost Basis by Origination Year 2019	13	29
Amortized Cost Basis by Origination Year, Prior to 2019	(46)	(57)
Total loans	(1,035)	(704)
Consumer [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	83	183
Amortized Cost Basis by Origination Year 2022	451	208
Amortized Cost Basis by Origination Year 2021	106	69
Amortized Cost Basis by Origination Year 2020	74	32
Amortized Cost Basis by Origination Year 2019	16	2
Amortized Cost Basis by Origination Year, Prior to 2019	(54)	(79)
Total loans	(784)	(573)
Consumer [Member] | Current-period gross charge-offs [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	73	769
Amortized Cost Basis by Origination Year 2022	1,305	1,237
Amortized Cost Basis by Origination Year 2021	681	624
Amortized Cost Basis by Origination Year 2020	240	333
Amortized Cost Basis by Origination Year 2019	79	186
Amortized Cost Basis by Origination Year, Prior to 2019	(223)	(326)
Revolving Loans	3
Revolving Loans Converted to Term		1
Total loans	(2,604)	(3,476)
Commercial Real Estate - Land and Construction [Member] | Current-period gross charge-offs [Member]
Financing Receivable, Recorded Investment [Line Items]
Revolving Loans Converted to Term	222
Total loans	(222)
Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	163,921	160,328
Amortized Cost Basis by Origination Year 2022	291,411	136,396
Amortized Cost Basis by Origination Year 2021	140,411	144,172
Amortized Cost Basis by Origination Year 2020	53,071	155,141
Amortized Cost Basis by Origination Year 2019	49,688	61,847
Amortized Cost Basis by Origination Year, Prior to 2019	(36,504)	(51,536)
Revolving Loans	89,731	117,237
Revolving Loans Converted to Term	45,329	117,230
Total loans	(870,066)	(943,887)
Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		(910)
Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		(741)
Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	163,921	159,769
Amortized Cost Basis by Origination Year 2022	291,411	136,131
Amortized Cost Basis by Origination Year 2021	140,411	138,171
Amortized Cost Basis by Origination Year 2020	53,071	155,141
Amortized Cost Basis by Origination Year 2019	49,688	61,823
Amortized Cost Basis by Origination Year, Prior to 2019	(36,474)	(51,381)
Revolving Loans	89,731	117,237
Revolving Loans Converted to Term	42,949	92,151
Total loans	(867,656)	(911,804)
Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member] | Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023		559
Amortized Cost Basis by Origination Year 2022		265
Amortized Cost Basis by Origination Year 2021
Amortized Cost Basis by Origination Year 2020
Amortized Cost Basis by Origination Year 2019		24
Amortized Cost Basis by Origination Year, Prior to 2019	(20)	(31)
Revolving Loans Converted to Term	2,380	450
Total loans	(2,400)	(1,329)
Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member] | Classified - substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2021		6,001
Amortized Cost Basis by Origination Year, Prior to 2019	(10)	(124)
Revolving Loans Converted to Term		24,629
Total loans	(10)	(30,754)
Commercial Real Estate - Land and Construction [Member] | Commercial Real Estate [Member] | Current-period gross charge-offs [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2019		73
Total loans		(73)
Commercial Real Estate - Improved Property [Member] | Current-period gross charge-offs [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year, Prior to 2019	(1,450)
Total loans	(1,450)
Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	401,664	1,093,538
Amortized Cost Basis by Origination Year 2022	1,101,388	621,217
Amortized Cost Basis by Origination Year 2021	627,560	616,815
Amortized Cost Basis by Origination Year 2020	616,447	551,152
Amortized Cost Basis by Origination Year 2019	552,317	395,192
Amortized Cost Basis by Origination Year, Prior to 2019	(1,860,985)	(1,666,522)
Revolving Loans	95,426	73,427
Revolving Loans Converted to Term	261,330	99,594
Total loans	(5,517,117)	(5,117,457)
Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(2,161)	(2,147)
Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(1,279)	(331)
Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(14,608)	(15,637)
Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	401,664	1,082,984
Amortized Cost Basis by Origination Year 2022	1,090,574	620,205
Amortized Cost Basis by Origination Year 2021	623,153	613,663
Amortized Cost Basis by Origination Year 2020	610,828	528,004
Amortized Cost Basis by Origination Year 2019	512,609	371,880
Amortized Cost Basis by Origination Year, Prior to 2019	(1,754,251)	(1,551,478)
Revolving Loans	93,421	72,327
Revolving Loans Converted to Term	240,134	99,594
Total loans	(5,326,634)	(4,940,135)
Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member] | Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023		10,554
Amortized Cost Basis by Origination Year 2022	10,300	354
Amortized Cost Basis by Origination Year 2021	3,938	2,877
Amortized Cost Basis by Origination Year 2020	2,855	7,659
Amortized Cost Basis by Origination Year 2019	3,964	13,551
Amortized Cost Basis by Origination Year, Prior to 2019	(81,658)	(85,332)
Revolving Loans	1,986	1,066
Revolving Loans Converted to Term	21,162
Total loans	(125,863)	(121,393)
Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member] | Classified - substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2022	514	658
Amortized Cost Basis by Origination Year 2021	469	275
Amortized Cost Basis by Origination Year 2020	2,764	15,489
Amortized Cost Basis by Origination Year 2019	35,744	9,761
Amortized Cost Basis by Origination Year, Prior to 2019	(25,076)	(29,712)
Revolving Loans	19	34
Revolving Loans Converted to Term	34
Total loans	(64,620)	(55,929)
Commercial Real Estate - Improved Property [Member] | Commercial Real Estate [Member] | Current-period gross charge-offs [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2021		128
Amortized Cost Basis by Origination Year 2020		100
Amortized Cost Basis by Origination Year 2019		3
Amortized Cost Basis by Origination Year, Prior to 2019		(564)
Total loans		(795)
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	169,586	281,520
Amortized Cost Basis by Origination Year 2022	255,697	189,206
Amortized Cost Basis by Origination Year 2021	151,563	118,136
Amortized Cost Basis by Origination Year 2020	93,556	82,577
Amortized Cost Basis by Origination Year 2019	54,985	104,021
Amortized Cost Basis by Origination Year, Prior to 2019	(298,651)	(237,440)
Revolving Loans	520,316	534,745
Revolving Loans Converted to Term	43,257	31,750
Total loans	(1,587,611)	(1,579,395)
Commercial and Industrial [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(566)	(1,427)
Commercial and Industrial [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(438)	(519)
Commercial and Industrial [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	(1,785)	(3,138)
Commercial and Industrial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	168,627	280,510
Amortized Cost Basis by Origination Year 2022	255,050	184,805
Amortized Cost Basis by Origination Year 2021	147,484	116,890
Amortized Cost Basis by Origination Year 2020	92,590	72,142
Amortized Cost Basis by Origination Year 2019	47,358	103,660
Amortized Cost Basis by Origination Year, Prior to 2019	(279,259)	(232,062)
Revolving Loans	504,659	526,025
Revolving Loans Converted to Term	34,344	22,206
Total loans	(1,529,371)	(1,538,300)
Commercial and Industrial [Member] | Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	959	917
Amortized Cost Basis by Origination Year 2022	512	1,192
Amortized Cost Basis by Origination Year 2021	4,020	270
Amortized Cost Basis by Origination Year 2020	359	8,278
Amortized Cost Basis by Origination Year 2019	6,786	264
Amortized Cost Basis by Origination Year, Prior to 2019	(17,317)	(2,524)
Revolving Loans	14,509	7,654
Revolving Loans Converted to Term	7,411	4,124
Total loans	(51,873)	(25,223)
Commercial and Industrial [Member] | Classified - substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023		93
Amortized Cost Basis by Origination Year 2022	135	3,209
Amortized Cost Basis by Origination Year 2021	59	976
Amortized Cost Basis by Origination Year 2020	607	2,157
Amortized Cost Basis by Origination Year 2019	841	97
Amortized Cost Basis by Origination Year, Prior to 2019	(2,075)	(2,854)
Revolving Loans	1,148	1,066
Revolving Loans Converted to Term	1,502	5,420
Total loans	(6,367)	(15,872)
Commercial and Industrial [Member] | Current-period gross charge-offs [Member]
Financing Receivable, Recorded Investment [Line Items]
Amortized Cost Basis by Origination Year 2023	98
Amortized Cost Basis by Origination Year 2022	143	16
Amortized Cost Basis by Origination Year 2021	563	234
Amortized Cost Basis by Origination Year 2020	43	275
Amortized Cost Basis by Origination Year 2019	20	70
Amortized Cost Basis by Origination Year, Prior to 2019	(387)	(182)
Revolving Loans Converted to Term	244	291
Total loans	$ (1,498)	$ (1,068)