Debt - Schedule of Principal Repayment under the Financing Agreement (Parenthetical) (Detail) $ in Thousands	Sep. 30, 2015 USD ($)
2017 [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Outstanding principal balance	$ 46,500

The amount necessary to repay the outstanding principal balance in full at the loan maturity date based on principal payments made through the reporting date and the scheduled principal repayment amounts through the loan maturity date.

No definition available.

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