Name:	esi_AppraisedValuePercentageOfProperties
Namespace Prefix:	esi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The amount of cash collateral provided by the reporting entity for issued letters of credit.

No definition available.

Name:	esi_CashCollateralForLettersOfCredit
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The total amount of the contingent obligation under the ED Letter of Credit outstanding as of the reporting date.

No definition available.

Name:	esi_EDLetterOfCreditOutstandingAmount
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The maximum amount of letters of credits available to be issued under the credit agreement.

No definition available.

Name:	esi_LettersOfCreditMaximum
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The maximum borrowing capacity under the credit facility that was revised as a result of an amendment to the credit agreement.

No definition available.

Name:	esi_LineOfCreditFacilityMaximumBorrowingCapacityRevised
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Number Of Parcels Of Land

No definition available.

Name:	esi_NumberOfParcelsOfLand
Namespace Prefix:	esi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The limitation on asset dispositions as specified in the credit facility prior to revision.

No definition available.

Name:	esi_PriorLimitationOnAssetDispositions
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of permitted indebtedness allowed under the original credit agreement.

No definition available.

Name:	esi_PriorPermittedIndebtedness
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The percentage of the amount of certain issued letters of credit that are required to be collateralized with cash.

No definition available.

Name:	esi_RequiredCashCollateralForLettersOfCredit1
Namespace Prefix:	esi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The percentage of the amount of certain issued letters of credit that are required to be collateralized with cash.

No definition available.

Name:	esi_RequiredCashCollateralForLettersOfCredit2
Namespace Prefix:	esi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The revised limitation on asset dispositions as specified in the amended credit facility.

No definition available.

Name:	esi_RevisedLimitationOnAssetDispositions
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The amount of permitted indebtedness allowed under the amended credit agreement.

No definition available.

Name:	esi_RevisedPermittedIndebtedness
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Additional fees paid to lenders for letter of credit exposures.

No definition available.

Name:	esi_TickingFeeRate
Namespace Prefix:	esi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Amount borrowed under the credit facility as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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

Date the credit facility terminates, in CCYY-MM-DD format.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

The effective interest rate during the reporting period.

Name:	us-gaap_LineOfCreditFacilityInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

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

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

No definition available.

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The gross proceeds received from the asset(s) sold in connection with the transaction involving the sale of property to another party and the lease of the property back to the seller less the costs incurred in connection with the transaction, such as closing and deferred financing costs.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 40

-Section 55

-Paragraph 51

-URI http://asc.fasb.org/extlink&oid=28365400&loc=d3e51840-112757

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 40

-Section 55

-Paragraph 52

-URI http://asc.fasb.org/extlink&oid=28365400&loc=d3e51843-112757

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 40

-Section 55

-Paragraph 50

-URI http://asc.fasb.org/extlink&oid=28365400&loc=d3e51831-112757

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

Name:	us-gaap_CreditFacilityAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_DebtInstrumentAxis=esi_AmendedCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_DebtInstrumentAxis=esi_CreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: