Long-term Debt and Line of Credit (Details) (USD $)	3 Months Ended
Mar. 31, 2015
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 11,400,000
Balance outstanding under revolver	22,500,000orn_Balanceoutstandingunderrevolver
Fixed charge coverage ratio	1.50orn_FixedChargeCoverageRatio
Leverage ratio	2.50orn_LeverageRatio
Debt instrument, description of variable rate basis	LIBOR
Line of credit facility, interest rate during period	2.38%
LIBOR
Debt Instrument [Line Items]
Line of credit facility, interest rate at period end	2.19%
Eligible accounts receivable
Debt Instrument [Line Items]
Line of credit, current borrowing capacity base components	80.00%
Adjusted cash balance
Debt Instrument [Line Items]
Line of credit, current borrowing capacity base components	90.00%
Secured Debt
Debt Instrument [Line Items]
Line of credit facility, additional borrowing capacity	25,000,000
Long-term debt	10,500,000
Principal loan payments	389,000
Line of credit facility, unused capacity commitment fee percentage	0.25%
Secured Debt \| Term Loan Two
Debt Instrument [Line Items]
Debt Instrument, Periodic Payment	53,000
Debt Instrument, Interest Rate, Stated Percentage	3.10%
Letter of credit \| Secured Debt
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity	20,000,000
Letters of credit outstanding, amount	1,100,000.000000000
Revolving Credit Facility \| Secured Debt \| Prime Rate Based Loans
Debt Instrument [Line Items]
Line of Credit Facility, Integral Multiple of Borrowings	500,000
Revolving Credit Facility \| Secured Debt \| Eurodollar Rate Loan
Debt Instrument [Line Items]
Line of Credit Facility, Integral Multiple of Borrowings	1,000,000
Swingline Loan \| Secured Debt \| Prime Rate Based Loans
Debt Instrument [Line Items]
Line of Credit Facility, Integral Multiple of Borrowings	100,000
Amended credit agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 35,000,000

balance outstanding under revolver

No definition available.

Name:	orn_Balanceoutstandingunderrevolver
Namespace Prefix:	orn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fixed Charge Coverage Ratio

+ References

No definition available.

+ Details

Name:	orn_FixedChargeCoverageRatio
Namespace Prefix:	orn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Leverage Ratio

+ References

No definition available.

+ Details

Name:	orn_LeverageRatio
Namespace Prefix:	orn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of Credit, Current Borrowing Capacity Base Components

+ References

No definition available.

+ Details

Name:	orn_LineOfCreditCurrentBorrowingCapacityBaseComponents
Namespace Prefix:	orn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of Credit Facility, Additional Borrowing Capacity

+ References

No definition available.

+ Details

Name:	orn_LineOfCreditFacilityAdditionalBorrowingCapacity
Namespace Prefix:	orn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of Credit Facility, Integral Multiple of Borrowings

+ References

No definition available.

+ Details

Name:	orn_LineOfCreditFacilityIntegralMultipleOfBorrowings
Namespace Prefix:	orn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Definition

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

+ References

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

+ Details

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

- Definition

Amount of the required periodic payments applied to principal.

+ References

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ 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 210.5-02.19(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

+ Details

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

- Definition

The effective interest rate at the end of the reporting period.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The effective interest rate during the reporting period.

+ References

+ Details

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

- Definition

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.

+ References

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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

- Details

Name:	orn_CreditFacilityNameAxis=orn_AmendedCreditAgreementOf2012Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	orn_LineOfCreditBorrowingCapacityBaseComponentsAxis=orn_AdjustedCashBalanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	orn_LineOfCreditBorrowingCapacityBaseComponentsAxis=orn_EligibleAccountsReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	orn_RevolvingCreditFacilityInterestRateOptionsAxis=orn_LiborMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: