Allowance for Credit Losses - Loan Modified to Borrowers Experiencing Financial Difficulty (Details) - USD ($)	3 Months Ended			6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Troubled debt restructuring modifications
Amortized Cost Basis			$ 2,423,000	$ 7,719,000
% of Total Class of Financing Receivable		0.01%
Commitments related to borrowers experiencing financial difficulty	$ 0			0
Aggregate commitments to extend credit, standby letters of credit and commercial letters of credit	6,400,000,000			6,400,000,000		$ 6,500,000,000
Commitments related to borrowers experiencing financial difficulty						$ 5,000,000.0
Financial Asset, 30 to 59 Days Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			34,000	152,000
Financial Asset, 60 to 89 Days Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis				53,000
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			33,000	31,000
Financial Asset, Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			67,000	236,000
Financial Asset, Not Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			2,356,000	7,483,000
Commercial and Industrial
Troubled debt restructuring modifications
Amortized Cost Basis			109,000	435,000
Commercial and Industrial | Financial Asset, Not Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			109,000	435,000
Construction
Troubled debt restructuring modifications
Amortized Cost Basis			230,000	653,000
Construction | Financial Asset, Not Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			230,000	653,000
Commercial Real Estate Portfolio Segment [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			1,229,000	2,685,000
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			1,229,000	2,685,000
Residential mortgage
Troubled debt restructuring modifications
Amortized Cost Basis			33,000	2,326,000
Residential mortgage | Financial Asset, Not Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			33,000	2,326,000
Consumer
Troubled debt restructuring modifications
Amortized Cost Basis			822,000	1,620,000
Consumer | Financial Asset, 30 to 59 Days Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			34,000	152,000
Consumer | Financial Asset, 60 to 89 Days Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis				53,000
Consumer | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			33,000	31,000
Consumer | Financial Asset, Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			67,000	236,000
Consumer | Financial Asset, Not Past Due [Member]
Troubled debt restructuring modifications
Amortized Cost Basis			$ 755,000	1,384,000
Interest Rate Reduction
Troubled debt restructuring modifications
Amortized Cost Basis	473,000	$ 371,000		1,043,000	$ 707,000
Amortized Cost Basis of Modified Loans That Subsequently Defaulted	397,000	87,000		467,000	88,000
Interest Rate Reduction | Commercial Real Estate Portfolio Segment [Member]
Troubled debt restructuring modifications
Amortized Cost Basis					$ 2,000
Reduced weighted-average contractual interest rate					0.75%
Interest Rate Reduction | Consumer
Troubled debt restructuring modifications
Amortized Cost Basis	$ 473,000	$ 371,000		$ 1,043,000	$ 705,000
% of Total Class of Financing Receivable	0.05%	0.03%		0.10%	0.06%
Reduced weighted-average contractual interest rate	13.61%	12.98%		13.57%	13.23%
Amortized Cost Basis of Modified Loans That Subsequently Defaulted	$ 397,000	$ 87,000		$ 467,000	$ 88,000
Term Extension
Troubled debt restructuring modifications
Amortized Cost Basis	$ 2,074,000	1,360,000		$ 2,685,000	$ 1,716,000
% of Total Class of Financing Receivable	0.01%			0.02%	0.01%
Amortized Cost Basis of Modified Loans That Subsequently Defaulted	$ 94,000			$ 94,000
Term Extension | Commercial and Industrial
Troubled debt restructuring modifications
Amortized Cost Basis	83,000	$ 87,000		$ 273,000	$ 109,000
% of Total Class of Financing Receivable				0.01%
Added weighted-average years to the life of loans		3 years 7 months 6 days	4 years 1 month 6 days	4 years 10 months 24 days	3 years 6 months
Amortized Cost Basis of Modified Loans That Subsequently Defaulted	74,000			$ 74,000
Term Extension | Construction
Troubled debt restructuring modifications
Amortized Cost Basis					$ 230,000
% of Total Class of Financing Receivable					0.03%
Added weighted-average years to the life of loans					2 years 10 months 24 days
Term Extension | Commercial Real Estate Portfolio Segment [Member]
Troubled debt restructuring modifications
Amortized Cost Basis	$ 1,184,000	$ 1,227,000		$ 1,184,000	$ 1,227,000
% of Total Class of Financing Receivable	0.03%	0.03%		0.03%	0.03%
Added weighted-average years to the life of loans	1 year	1 year		1 year	1 year
Term Extension | Residential mortgage
Troubled debt restructuring modifications
Amortized Cost Basis	$ 792,000			$ 1,099,000	$ 33,000
% of Total Class of Financing Receivable	0.02%			0.03%
Added weighted-average years to the life of loans			9 months 18 days	8 months 12 days	5 years 10 months 24 days
Term Extension | Consumer
Troubled debt restructuring modifications
Amortized Cost Basis	$ 15,000	$ 46,000		$ 129,000	$ 117,000
% of Total Class of Financing Receivable				0.01%	0.01%
Added weighted-average years to the life of loans	2 years 10 months 24 days	2 years 3 months 18 days		4 years 1 month 6 days	3 years 7 months 6 days
Amortized Cost Basis of Modified Loans That Subsequently Defaulted	$ 20,000			$ 20,000
Other-Than-Insignificant Payment Delay
Troubled debt restructuring modifications
Amortized Cost Basis				1,226,000
Other-Than-Insignificant Payment Delay | Residential mortgage
Troubled debt restructuring modifications
Amortized Cost Basis				$ 1,226,000
% of Total Class of Financing Receivable				0.03%
Deferred loan payments				$ 172,000