Long-term Debt and Line of Credit - Financial covenants (Details)	12 Months Ended
Dec. 31, 2020
Debt Disclosure [Abstract]
Covenant compliance, Fixed Charge Coverage Ratio, minimum	1.25
Covenant compliance, Leverage Ratio, maximum	3.00

Minimum Fixed Charge Coverage Ratio that is to be maintained per terms of the financial covenants of the Credit Facility.

No definition available.

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