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Concentration of Risk and Enterprise Wide Disclosures (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Concentration Risk [Line Items]                      
Contract revenues $ 107,333us-gaap_ContractsRevenue $ 106,976us-gaap_ContractsRevenue $ 90,251us-gaap_ContractsRevenue $ 81,258us-gaap_ContractsRevenue $ 106,412us-gaap_ContractsRevenue $ 88,992us-gaap_ContractsRevenue $ 84,081us-gaap_ContractsRevenue $ 75,059us-gaap_ContractsRevenue $ 385,818us-gaap_ContractsRevenue $ 354,544us-gaap_ContractsRevenue $ 292,042us-gaap_ContractsRevenue
Foreign                      
Concentration Risk [Line Items]                      
Contract revenues, percent                 12.90%orn_ContractsRevenuePercent
/ us-gaap_StatementGeographicalAxis
= orn_ForeignMember		 8.50%orn_ContractsRevenuePercent
/ us-gaap_StatementGeographicalAxis
= orn_ForeignMember		 4.00%orn_ContractsRevenuePercent
/ us-gaap_StatementGeographicalAxis
= orn_ForeignMember
Customer concentration risk | Trade and contract retainage receivables                      
Concentration Risk [Line Items]                      
Trade and retainage receivables 52,788orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		       49,537orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		       52,788orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		 49,537orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		  
Concentration risk, percentage                 100.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		   100.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
Customer concentration risk | Contract revenues                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                 100.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		 100.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		 100.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
Contract revenues                 385,818us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		 354,544us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		 292,042us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
Customer concentration risk | Private sector customer | Trade and contract retainage receivables                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                 14.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= orn_PrivateSectorCustomerMember		 9.90%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= orn_PrivateSectorCustomerMember		  
Customer concentration risk | Private sector customer | Contract revenues                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                     10.70%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= orn_PrivateSectorCustomerMember
Customer concentration risk | US Army Corps of Engineers | Contract revenues                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                   11.70%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= orn_USArmyCorpsOfEngineersMember		 16.70%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= orn_USArmyCorpsOfEngineersMember
Customer concentration risk | Federal Government | Trade and contract retainage receivables                      
Concentration Risk [Line Items]                      
Trade and retainage receivables 4,607orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeFederalMember		       4,849orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeFederalMember		       4,607orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeFederalMember		 4,849orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeFederalMember		  
Concentration risk, percentage                 9.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeFederalMember		   10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeFederalMember
Customer concentration risk | Federal Government | Contract revenues                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                 13.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeFederalMember		 19.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeFederalMember		 22.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeFederalMember
Contract revenues                 47,390us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeFederalMember		 65,926us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeFederalMember		 64,049us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeFederalMember
Customer concentration risk | State Governments | Trade and contract retainage receivables                      
Concentration Risk [Line Items]                      
Trade and retainage receivables 476orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeStateMember		       4,002orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeStateMember		       476orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeStateMember		 4,002orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeStateMember		  
Concentration risk, percentage                 1.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeStateMember		   8.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeStateMember
Customer concentration risk | State Governments | Contract revenues                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                 11.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeStateMember		 9.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeStateMember		 12.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeStateMember
Contract revenues                 43,147us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeStateMember		 30,451us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeStateMember		 35,799us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeStateMember
Customer concentration risk | Local Governments | Trade and contract retainage receivables                      
Concentration Risk [Line Items]                      
Trade and retainage receivables 13,927orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeLocalMember		       8,857orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeLocalMember		       13,927orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeLocalMember		 8,857orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeLocalMember		  
Concentration risk, percentage                 26.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeLocalMember		   18.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeLocalMember
Customer concentration risk | Local Governments | Contract revenues                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                 25.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeLocalMember		 15.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeLocalMember		 15.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeLocalMember
Contract revenues                 97,145us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeLocalMember		 54,702us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeLocalMember		 44,626us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypeLocalMember
Customer concentration risk | Private Companies | Trade and contract retainage receivables                      
Concentration Risk [Line Items]                      
Trade and retainage receivables 33,778orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypePrivateMember		       31,829orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypePrivateMember		       33,778orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypePrivateMember		 31,829orn_TradeAccountsReceivableAndContractReceivableRetainageNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypePrivateMember		  
Concentration risk, percentage                 64.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypePrivateMember		   64.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= orn_TradeAndContractRetainageReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypePrivateMember
Customer concentration risk | Private Companies | Contract revenues                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                 51.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypePrivateMember		 57.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypePrivateMember		 51.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypePrivateMember
Contract revenues                 $ 198,136us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypePrivateMember		 $ 203,465us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypePrivateMember		 $ 147,568us-gaap_ContractsRevenue
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueServicesNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ orn_CustomerByTypeAxis
= orn_CustomerTypePrivateMember