v3.19.1

Commitments and Contingencies -Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Apr. 30, 2017 ft²
Operating Leased Assets [Line Items]
Deferred rent liability	$ 1.2	$ 0.9
Sublease agreement, area of general office space | ft²			7,735
Amount recognized under sublease	0.3	0.3
Rent expense	2.1	1.7
Security deposits	$ 0.4	$ 0.4
Cambridge, Massachusetts [Member]
Operating Leased Assets [Line Items]
Operating lease expiration period	2024-09
Cambridge, Massachusetts [Member] | Additional Space [Member]
Operating Leased Assets [Line Items]
Operating lease commencement period	2019-03
Extended operating lease expiration period	2024-09
Woburn Massachusetts [Member]
Operating Leased Assets [Line Items]
Operating lease expiration period	2022-01

X

- Definition

Date which lease is set to commence, in CCYY-MM format.

+ References

No definition available.

+ Details

Name:	ever_OperatingLeaseCommencingMonthYear
Namespace Prefix:	ever_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Date which lease is set to expire, in CCYY-MM format.

+ References

No definition available.

+ Details

Name:	ever_OperatingLeaseExpirationMonthYear
Namespace Prefix:	ever_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Date which lease is set to expire, in CCYY-MM format.

+ References

No definition available.

+ Details

Name:	ever_OperatingLeaseExpirationMonthYearOne
Namespace Prefix:	ever_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The cumulative difference between the rental payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense over the term of the leased property by the lessor or lessee, respectively.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=77902458&loc=d3e39896-112707

+ Details

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

X

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

X

- Definition

The amount of revenue recognized for the period under subleasing arrangements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 55
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=77891322&loc=d3e41620-112719

+ Details

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

X

- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41499-112717

+ Details

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

X

- Definition

The amount of an asset, typically cash, provided to a counterparty to provide certain assurance of performance by the entity pursuant to the terms of a written or oral agreement, such as a lease.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.8,17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

X

- Details

Name:	srt_StatementGeographicalAxis=ever_CambridgeMassachusettsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LeaseArrangementTypeAxis=ever_AdditionalSpaceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_StatementGeographicalAxis=ever_WoburnMassachusettsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: