Capital and Regulatory Matters - Actual Capital Amounts and Ratios (Details) $ in Thousands	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Origin Bancorp, Inc.
Common Equity Tier 1 Capital to Risk-Weighted Assets
Actual, amount	$ 1,034,347	$ 1,012,916
Actual, ratio	0.1197	0.1183
Minimum capital required, amount	$ 604,669	$ 599,455
Minimum capital required, ratio	0.0700	0.0700
Tier 1 Capital to Risk-Weighted Assets
Actual, amount	$ 1,050,183	$ 1,028,729
Actual, ratio	0.1215	0.1201
Minimum capital required, amount	$ 734,696	$ 727,907
Minimum capital required, ratio	0.0850	0.0850
Total Capital to Risk-Weighted Assets
Actual, amount	$ 1,294,542	$ 1,286,604
Actual, ratio	0.1498	0.1502
Minimum capital required, amount	$ 907,389	$ 899,184
Minimum capital required, ratio	0.1050	0.1050
Leverage Ratio
Actual, amount	$ 1,050,183	$ 1,028,729
Actual, ratio	0.1066	0.1050
Minimum capital required, amount	$ 393,987	$ 391,822
Minimum capital required, ratio	0.0400	0.0400
Origin Bank | Origin Bank
Common Equity Tier 1 Capital to Risk-Weighted Assets
Actual, amount	$ 1,040,139	$ 1,019,732
Actual, ratio	0.1208	0.1195
Minimum capital required, amount	$ 602,730	$ 597,548
Minimum capital required, ratio	0.0700	0.0700
Well capitalized, amount	$ 559,677	$ 554,866
Well capitalized, ratio	6.50%	6.50%
Tier 1 Capital to Risk-Weighted Assets
Actual, amount	$ 1,040,139	$ 1,019,732
Actual, ratio	0.1208	0.1195
Minimum capital required, amount	$ 731,886	$ 725,593
Minimum capital required, ratio	0.0850	0.0850
To be well capitalized under prompt corrective action provisions, amount	$ 688,834	$ 682,912
To be well capitalized under prompt corrective action provisions, ratio	0.0800	0.0800
Total Capital to Risk-Weighted Assets
Actual, amount	$ 1,209,498	$ 1,188,000
Actual, ratio	0.1405	0.1392
Minimum capital required, amount	$ 903,968	$ 896,320
Minimum capital required, ratio	0.1050	0.1050
To be well capitalized under prompt corrective action provisions, amount	$ 860,922	$ 853,638
To be well capitalized under prompt corrective action provisions, ratio	0.1000	0.1000
Leverage Ratio
Actual, amount	$ 1,040,139	$ 1,019,732
Actual, ratio	0.1060	0.1045
Minimum capital required, amount	$ 392,550	$ 390,246
Minimum capital required, ratio	0.0400	0.0400
To be well capitalized under prompt corrective action provisions, amount	$ 490,687	$ 487,807
To be well capitalized under prompt corrective action provisions, ratio	0.0500	0.0500