Regulatory Matters (Details)	Dec. 31, 2019	Dec. 31, 2018
Enterprise Financial Services Corp [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual, Ratio	12.90%	13.02%
Tier 1 Capital (to Risk Weighted Assets) [Abstract]
Actual, Ratio	11.40%	11.14%
Tier One Common Equity Capital to Risk Weighted Assets	9.90%	9.79%
Tier 1 Capital (to Average Assets) [Abstract]
Actual, Ratio	10.05%	10.29%
Enterprise Bank and Trust [Member]
Total Capital (to Risk Weighted Assets) [Abstract]
Actual, Ratio	12.40%	12.26%
To Be Well Capitalized Under Applicable Action Provisions, Ratio	10.00%
Capital to Risk Weighted Assets CCB Minimum	10.50%
Tier 1 Capital (to Risk Weighted Assets) [Abstract]
Actual, Ratio	11.70%	11.38%
To Be Well Capitalized Under Applicable Action Provisions, Ratio	8.00%
Tier One Risk Based Capital CCB Minimum	8.50%
Tier One Common Equity Capital to Risk Weighted Assets	11.69%	11.37%
Tier One Common Equity Capital Required to be Well Capitalized to Risk Weighted Assets	6.50%
Tier One Common Equity Capital CCB Minimum	7.00%
Tier 1 Capital (to Average Assets) [Abstract]
Actual, Ratio	10.31%	10.52%
To Be Well Capitalized Under Applicable Action Provisions, Ratio	5.00%
Tier One Leverage Capital to Average Assets CCB Minimum	4.00%