Stock Options and Restricted Shares - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Closing common stock price (usd per share)	$ 1.16
Compensation cost related to non-vested common stock-based compensation	$ 0.2
Weighted average expected term	1 year 3 months 7 days
Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of stock based compensation issued during the period (shares)	771,252	485,184
Stock issued in lieu of cash compensation (shares)	57,065
Weighted-average per share price on grant date (usd per share)	$ 1.38
Deferred stock-based compensation related to grants of restricted shares, period of recognition	2 years 5 months 18 days
Deferred stock-based compensation related to grants of restricted shares	$ 2.5
Minimum \| Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average per share price on grant date (usd per share)	$ 1.38	$ 2.21
Weighted-average per share price on grant date (usd per share)	1.34
Maximum \| Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average per share price on grant date (usd per share)	1.50	$ 2.62
Weighted-average per share price on grant date (usd per share)	$ 6.80
2003 Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved shares for issuance to key employees (shares)	13,500,000

Deferred compensation arrangement with individual compensation expense period of recognition.

No definition available.

Name:	oesx_DeferredCompensationArrangementWithIndividualCompensationExpensePeriodOfRecognition
Namespace Prefix:	oesx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of closing common stock price.

+ References

No definition available.

+ Details

Name:	oesx_FairValueOfClosingCommonStockPrice
Namespace Prefix:	oesx_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Share based compensation arrangement by share based payment award per share price.

+ References

No definition available.

+ Details

Name:	oesx_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerSharePrice
Namespace Prefix:	oesx_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Aggregate number of common shares reserved for future issuance.

+ References

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 210.5-02.29)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockCapitalSharesReservedForFutureIssuance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The compensation expense recognized during the period pertaining to the deferred compensation arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-SubTopic 10
-Section 30
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363

+ Details

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

- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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

- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

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

- Definition

Number of share instruments newly issued under a share-based compensation plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares issued in lieu of cash for services contributed to the entity. Number of shares includes, but is not limited to, shares issued for services contributed by vendors and founders.

+ References

No definition available.

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesIssuedForServices
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_PlanNameAxis=oesx_TwoThousandThreeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: