Loans and Allowance for Credit Losses - Age Analysis of Past Due Loans Segregated by Class of Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Total	$ 7,689,054	$ 7,653,341
Nonaccrual	31,889	22,947	$ 19,052
Current
Financing Receivable, Past Due [Line Items]
Total	7,641,226	7,615,273
Total Past Due Loans
Financing Receivable, Past Due [Line Items]
Total	47,828	38,068
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	10,374	7,247
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	5,565	7,874
Commercial Loans \| Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	2,660,816	2,659,135
Nonaccrual	14,171	6,320	7,100
Commercial Loans \| Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	1,363,477	1,436,183
Nonaccrual	3,302	878	283
Commercial Loans \| Commercial construction
Financing Receivable, Past Due [Line Items]
Total	374,299	350,583
Nonaccrual	3,416	4,960	384
Commercial Loans \| Business banking
Financing Receivable, Past Due [Line Items]
Total	1,291,080	1,360,765
Nonaccrual	3,903	4,147	4,490
Commercial Loans \| Current \| Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	2,646,645	2,649,412
Commercial Loans \| Current \| Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	1,352,497	1,435,301
Commercial Loans \| Current \| Commercial construction
Financing Receivable, Past Due [Line Items]
Total	370,883	345,623
Commercial Loans \| Current \| Business banking
Financing Receivable, Past Due [Line Items]
Total	1,284,828	1,351,048
Commercial Loans \| Total Past Due Loans \| Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	14,171	9,723
Commercial Loans \| Total Past Due Loans \| Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	10,980	882
Commercial Loans \| Total Past Due Loans \| Commercial construction
Financing Receivable, Past Due [Line Items]
Total	3,416	4,960
Commercial Loans \| Total Past Due Loans \| Business banking
Financing Receivable, Past Due [Line Items]
Total	6,252	9,717
Commercial Loans \| 30-59 Days Past Due \| Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial Loans \| 30-59 Days Past Due \| Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	7,678	4
Commercial Loans \| 30-59 Days Past Due \| Commercial construction
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial Loans \| 30-59 Days Past Due \| Business banking
Financing Receivable, Past Due [Line Items]
Total	430	3,525
Commercial Loans \| 60-89 Days Past Due \| Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	0	3,403
Commercial Loans \| 60-89 Days Past Due \| Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial Loans \| 60-89 Days Past Due \| Commercial construction
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial Loans \| 60-89 Days Past Due \| Business banking
Financing Receivable, Past Due [Line Items]
Total	1,919	2,045
Consumer Loans \| Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	1,894,147	1,731,778
Nonaccrual	6,833	6,312	6,526
Consumer Loans \| Other consumer
Financing Receivable, Past Due [Line Items]
Total	105,235	114,897
Nonaccrual	264	330	$ 269
Consumer Loans \| Current \| Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	1,881,657	1,719,751
Consumer Loans \| Current \| Other consumer
Financing Receivable, Past Due [Line Items]
Total	104,716	114,138
Consumer Loans \| Total Past Due Loans \| Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	12,490	12,027
Consumer Loans \| Total Past Due Loans \| Other consumer
Financing Receivable, Past Due [Line Items]
Total	519	759
Consumer Loans \| 30-59 Days Past Due \| Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	2,106	3,352
Consumer Loans \| 30-59 Days Past Due \| Other consumer
Financing Receivable, Past Due [Line Items]
Total	160	366
Consumer Loans \| 60-89 Days Past Due \| Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	3,551	2,363
Consumer Loans \| 60-89 Days Past Due \| Other consumer
Financing Receivable, Past Due [Line Items]
Total	$ 95	$ 63