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Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
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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 amount of cash collateral that was provided by the reporting entity at the time a new financing agreement was entered into for issued letters of credit.

No definition available.

Name:	esi_CashCollateralForLettersOfCreditPaidAtFinancing
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Debt instrument base rate percentage.

No definition available.

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

Maximum amount of guarantee payments allowed under financial covenants in any future fiscal year.

No definition available.

Name:	esi_DebtInstrumentCovenantAmountFuturePeriods
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Maximum amount of guarantee payments allowed under financial covenants in any future fiscal year after the next fiscal year.

No definition available.

Name:	esi_DebtInstrumentCovenantAmountFuturePeriodsAfterNextFiscalYear
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Maximum amount of guarantee payments allowed under financial covenants in next fiscal year.

No definition available.

Name:	esi_DebtInstrumentCovenantAmountInNextFiscalYear
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Debt instrument prepayment premium percentage.

No definition available.

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

The amount of the required quarterly administrative fee.

No definition available.

Name:	esi_DebtInstrumentQuarterlyAdministrativeFee
Namespace Prefix:	esi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The period of time after entering into an agreement that excess cash flow must be paid to a lender.

No definition available.

Name:	esi_ExcessCashFlowTerm
Namespace Prefix:	esi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The percentage of excess cash flow, as defined in an agreement, that is required to be paid to a lender.

No definition available.

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

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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Period Type:	duration

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

No definition available.

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

Face (par) amount of debt instrument at time of issuance.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

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Period Type:	instant

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
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Period Type:	duration

Latest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

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Data Type:	xbrli:dateItemType
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Period Type:	duration

Amount of the required periodic payments including both interest and principal payments.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

Represents the charge against earnings during the period for commitment fees and debt issuance expenses.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 8

-Article 5

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

Amount of cash outflow for payment of an obligation from a lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(f))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph f

-Article 4

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

Name:	us-gaap_RepaymentsOfLinesOfCredit
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Name:	us-gaap_DebtInstrumentAxis=esi_OptionOneMember
Namespace Prefix:
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Name:	us-gaap_DebtInstrumentAxis=esi_OptionTwoMember
Namespace Prefix:
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Namespace Prefix:
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