Portfolio Loans - Summary of Portfolio Loans Individually Evaluated for Impairment by Category (Details) - Portfolio loans, net - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	$ 11,512	$ 25,497
Recorded Investment With No Allowance	6,932	6,741
Recorded Investment With Allowance	2,975	16,249
Total Recorded Investment	9,907	22,990
Related Allowance	2,205	2,394
Average Recorded Investment	16,341	18,607
Commercial and industrial
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	3,702	8,042
Recorded Investment With No Allowance	658	2,609
Recorded Investment With Allowance	2,433	3,464
Total Recorded Investment	3,091	6,073
Related Allowance	1,802	704
Average Recorded Investment	5,696	4,136
Commercial - owner occupied
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	321	1,376
Recorded Investment With No Allowance	240	770
Recorded Investment With Allowance	0	519
Total Recorded Investment	240	1,289
Related Allowance	0	286
Average Recorded Investment	967	1,281
Commercial - investor owned
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	3,047	5,036
Recorded Investment With No Allowance	2,437	0
Recorded Investment With Allowance	0	5,187
Total Recorded Investment	2,437	5,187
Related Allowance	0	0
Average Recorded Investment	1,294	4,375
Construction and land development
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	3,728	7,961
Recorded Investment With No Allowance	2,862	419
Recorded Investment With Allowance	542	6,929
Total Recorded Investment	3,404	7,348
Related Allowance	403	352
Average Recorded Investment	5,934	7,280
Residential real estate
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	714	3,082
Recorded Investment With No Allowance	735	2,943
Recorded Investment With Allowance	0	150
Total Recorded Investment	735	3,093
Related Allowance	0	1,052
Average Recorded Investment	2,450	954
Consumer and other
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	0	0
Recorded Investment With No Allowance	0	0
Recorded Investment With Allowance	0	0
Total Recorded Investment	0	0
Related Allowance	0	0
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: