Allowance for Credit Losses - Age Analysis of Past Due Loans Segregated by Class of Loans (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) loan	Sep. 30, 2022 USD ($)	Dec. 31, 2020 USD ($)
Financing Receivable, Past Due [Line Items]
Total	$ 6,999,990	$ 7,096,916
Non - performing	$ 66,291	22,777	$ 146,774
Number of modified loans | loan	8
Modified loans	$ 28,800
Current
Financing Receivable, Past Due [Line Items]
Total	6,927,943	7,067,800
Total Past Due Loans
Financing Receivable, Past Due [Line Items]
Total	72,047	29,116
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	3,085	2,910
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	2,671	3,429
Commercial Loans
Financing Receivable, Past Due [Line Items]
Total	5,406,584	5,239,648
Commercial Loans | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	2,690,528	2,562,582
Non - performing	31,488	7,833	101,070
Commercial Loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	1,513,523	1,501,879
Non - performing	15,239	335	16,985
Commercial Loans | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	424,755	375,279
Non - performing	2,471	384	384
Commercial Loans | Business banking
Financing Receivable, Past Due [Line Items]
Total	1,135,693	1,177,603
Non - performing	9,641	6,445	17,122
Commercial Loans | Current | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	2,659,040	2,554,749
Commercial Loans | Current | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	1,497,755	1,501,512
Commercial Loans | Current | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	421,834	374,895
Commercial Loans | Current | Business banking
Financing Receivable, Past Due [Line Items]
Total	1,124,748	1,168,727
Commercial Loans | Total Past Due Loans | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	31,488	7,833
Commercial Loans | Total Past Due Loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	15,768	367
Commercial Loans | Total Past Due Loans | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	2,921	384
Commercial Loans | Total Past Due Loans | Business banking
Financing Receivable, Past Due [Line Items]
Total	10,945	8,876
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	529	29
Commercial Loans | 30-59 Days Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	450	0
Commercial Loans | 30-59 Days Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Total	813	574
Commercial Loans | 60-89 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial Loans | 60-89 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	0	3
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	491	1,857
Consumer Loans
Financing Receivable, Past Due [Line Items]
Total	1,593,406	1,857,268
Consumer Loans | Business banking
Financing Receivable, Past Due [Line Items]
Total	357,900
Consumer Loans | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	1,127,585	1,352,965
Non - performing	7,294	7,373	11,117
Consumer Loans | Other Consumer
Financing Receivable, Past Due [Line Items]
Total	107,906	126,608
Non - performing	158	407	$ 96
Consumer Loans | Current | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	1,117,074	1,341,890
Consumer Loans | Current | Other Consumer
Financing Receivable, Past Due [Line Items]
Total	107,492	126,027
Consumer Loans | Total Past Due Loans | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	10,511	11,075
Consumer Loans | Total Past Due Loans | Other Consumer
Financing Receivable, Past Due [Line Items]
Total	414	581
Consumer Loans | 30-59 Days Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	1,087	2,188
Consumer Loans | 30-59 Days Past Due | Other Consumer
Financing Receivable, Past Due [Line Items]
Total	206	119
Consumer Loans | 60-89 Days Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	2,130	1,514
Consumer Loans | 60-89 Days Past Due | Other Consumer
Financing Receivable, Past Due [Line Items]
Total	$ 50	$ 55