Portfolio Loans - Summary of Portfolio Loans Individually Evaluated for Impairment by Category (Details) - Non-Covered Loans - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	$ 11,864	$ 25,497
Recorded Investment With No Allowance	5,072	6,741
Recorded Investment With Allowance	4,915	16,249
Total Recorded Investment	9,987	22,990
Related Allowance	2,335	2,394
Average Recorded Investment	11,924	18,607
Commercial and industrial
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	5,554	8,042
Recorded Investment With No Allowance	509	2,609
Recorded Investment With Allowance	4,204	3,464
Total Recorded Investment	4,713	6,073
Related Allowance	1,953	704
Average Recorded Investment	6,970	4,136
Commercial - Owner Occupied
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	329	610
Recorded Investment With No Allowance	85	0
Recorded Investment With Allowance	113	519
Total Recorded Investment	198	519
Related Allowance	6	0
Average Recorded Investment	301	1,281
Commercial - Investor Owned
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	927	5,036
Recorded Investment With No Allowance	927	0
Recorded Investment With Allowance	0	5,187
Total Recorded Investment	927	5,187
Related Allowance	0	0
Average Recorded Investment	970	4,375
Construction and land development
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	4,349	7,961
Recorded Investment With No Allowance	2,914	419
Recorded Investment With Allowance	530	6,929
Total Recorded Investment	3,444	7,348
Related Allowance	369	352
Average Recorded Investment	3,001	7,280
Residential real estate
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	705	3,082
Recorded Investment With No Allowance	637	2,943
Recorded Investment With Allowance	68	150
Total Recorded Investment	705	3,093
Related Allowance	7	1,052
Average Recorded Investment	682	954
Consumer and other
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	0	766
Recorded Investment With No Allowance	0	770
Recorded Investment With Allowance	0	0
Total Recorded Investment	0	770
Related Allowance	0	286
Average Recorded Investment	$ 0	$ 581

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableImpairedLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5258-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953550-111524

+ Details

Name:	us-gaap_ImpairedFinancingReceivableRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	efsc_LoansByMajorCategoryAxis=efsc_NoncoveredLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=efsc_CommercialAndIndustrialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=efsc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=efsc_CommercialRealEstateInvestorOwnedFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=efsc_ConstructionAndLandDevelopmentFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=efsc_ResidentialRealEstateFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=efsc_ConsumerAndOtherPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: