Nature of Business Activities and Significant Accounting Policies - Narrative (Details)		12 Months Ended
	Aug. 24, 2023 shares	Dec. 31, 2023 USD ($) branch segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of branches | branch		23
Reserve balance requirements		$ 0	$ 0
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]		Accrued interest receivable
Accrued interest receivable on available-for-sale debt securities		$ 7,500,000
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]		Accrued interest receivable
Accrued interest receivable on loans		$ 8,800,000
Number of operating segment | segment		1
Number of reportable segment | segment		1
Allowance for credit losses on loans		$ 25,301,000	21,039,000	$ 31,709,000	$ 32,697,000
Decrease in retained earnings, net of deferred taxes		$ (427,333,000)	(424,391,000)
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans			4,125,000
Credit losses on unfunded commitments			274,800
Decrease in retained earnings, net of deferred taxes			$ 3,400,000
Summit Financial Group, Inc
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common stock portion, number of Burke & Herbert stock for each share of Summit common stock converted (in shares) | shares	0.5043
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Term of issuance of loan commitment		15 days
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Term of issuance of loan commitment		90 days
Building and Building Improvements
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life		40 years
Furniture and Fixtures | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life		3 years
Furniture and Fixtures | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life		10 years
Burke & Herbert Bank & Trust Company
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Subsidiary, ownership percentage, parent		100.00%