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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Amount of Tier 1 leverage capital as defined by regulatory framework.

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Ratio of minimum Tier 1 leverage capital to average assets required for capital adequacy as defined by regulatory framework.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
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Ratio of Tier 1 capital to average assets as defined by regulatory framework.

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Regulatory Matters - Narrative (Details) $ in Thousands	Mar. 31, 2026 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2019 USD ($)
BancPlus Corporation
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital to Average Assets	$ 859,629	$ 862,204
Tier 1 Capital to Average Assets, ratio (as a percentage)	0.1059	0.1091
Tier 1 Capital to Average Assets, ratio (as a percentage)	0.09	0.09
BancPlus Corporation \| Maximum
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital to Average Assets			$ 10,000,000
BancPlus Corporation \| Minimum
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital to Average Assets, ratio (as a percentage)			0.09
Subsidiaries
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital to Average Assets	$ 873,989	$ 844,129
Tier 1 Capital to Average Assets, ratio (as a percentage)	0.1077	0.1067
Tier 1 Capital to Average Assets, ratio (as a percentage)	0.09	0.09