Loans and Allowance for Loan Losses (Allowance For Loan Losses By Segment) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 4,411	$ 4,505	$ 4,505
Charge-Offs	(186)	(210)	(370)
Recoveries	240	908	901
(Recovery of) provision for loan losses	248	(759)	(625)
Ending Balance	4,713	4,444	4,411
Ending balance: Individually evaluated for impairment	213		458
Ending balance: collectively evaluated for impairment	4,500		3,953
Loans Ending Balance	598,899		569,238
Ending balance individually evaluated for impairment	6,361		11,426
Ending balance collectively evaluated for impairment	592,538		557,812
Construction and Farmland
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	332	450	450
Charge-Offs	0		(19)
Recoveries	28		535
(Recovery of) provision for loan losses	256		(634)
Ending Balance	616		332
Ending balance: Individually evaluated for impairment	0		0
Ending balance: collectively evaluated for impairment	616		332
Loans Ending Balance	62,562		52,354
Ending balance individually evaluated for impairment	290		315
Ending balance collectively evaluated for impairment	62,272		52,039
Residential
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,754	1,992	1,992
Charge-Offs	(3)		(55)
Recoveries	24		212
(Recovery of) provision for loan losses	51		(395)
Ending Balance	1,826		1,754
Ending balance: Individually evaluated for impairment	158		195
Ending balance: collectively evaluated for impairment	1,668		1,559
Loans Ending Balance	229,330		227,305
Ending balance individually evaluated for impairment	4,425		8,315
Ending balance collectively evaluated for impairment	224,905		218,990
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,627	1,522	1,522
Charge-Offs	0		(1)
Recoveries	75		65
(Recovery of) provision for loan losses	77		41
Ending Balance	1,779		1,627
Ending balance: Individually evaluated for impairment	55		59
Ending balance: collectively evaluated for impairment	1,724		1,568
Loans Ending Balance	252,539		239,915
Ending balance individually evaluated for impairment	1,266		1,904
Ending balance collectively evaluated for impairment	251,273		238,011
Commercial - Non Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	570	235	235
Charge-Offs	(122)		(187)
Recoveries	85		44
(Recovery of) provision for loan losses	(213)		478
Ending Balance	320		570
Ending balance: Individually evaluated for impairment	0		195
Ending balance: collectively evaluated for impairment	320		375
Loans Ending Balance	36,549		37,427
Ending balance individually evaluated for impairment	379		858
Ending balance collectively evaluated for impairment	36,170		36,569
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	69	69	69
Charge-Offs	(28)		(59)
Recoveries	16		40
(Recovery of) provision for loan losses	5		19
Ending Balance	62		69
Ending balance: Individually evaluated for impairment	0		9
Ending balance: collectively evaluated for impairment	62		60
Loans Ending Balance	9,367		10,187
Ending balance individually evaluated for impairment	1		34
Ending balance collectively evaluated for impairment	9,366		10,153
All Other Loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	29	22	22
Charge-Offs	(33)		(49)
Recoveries	12		5
(Recovery of) provision for loan losses	102		51
Ending Balance	110		29
Ending balance: Individually evaluated for impairment	0		0
Ending balance: collectively evaluated for impairment	110		29
Loans Ending Balance	8,552		2,050
Ending balance individually evaluated for impairment	0		0
Ending balance collectively evaluated for impairment	8,552		2,050
Unallocated
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	30	$ 215	215
(Recovery of) provision for loan losses	(30)		(185)
Ending Balance	0		30
Ending balance: collectively evaluated for impairment	$ 0		$ 30

A valuation allowance for financing receivables that are expected to be uncollectible.

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

- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

+ Details

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

- Definition

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

+ References

+ Details

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

- Definition

Amount of recovery of financing receivables doubtful of collection that were previously charged off.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount of direct write-downs of financing receivables charged against the allowance.

+ References

+ Details

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

- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

+ Details

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

- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

+ Details

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

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

+ Details

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

- Definition

Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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