XML 46 R50.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Summary of Significant Accounting Policies - Net Changes in Capitalized Exploratory Well Costs (Detail) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Capitalized Costs Relating To Oil And Gas Properties [Roll Forward] |  |  |
Beginning of period | $ 40,424 | $ 20,207 | $ 5,176
Exploratory well cost additions (pending determination of proved reserves) | 346,814 | 160,813 | 73,947
Exploratory well cost reclassifications (successful determination of proved reserves) | (264,023) | (140,091) | (57,646)
Exploratory well dry hole costs (unsuccessful in adding proved reserves) |  | (505) | (1,270)
End of period | $ 123,215 | $ 40,424 | $ 20,207

X
- Details
Name: | oas_CapitalizedCostsRelatingToOilAndGasPropertiesRollForward
Namespace Prefix: | oas_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Additions to capitalized exploratory well costs that were added during the reporting period pending the determination of proved reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447 + Details
Name: | us-gaap_CapitalizedExploratoryWellCostAdditionsPendingDeterminationOfProvedReserves
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of capitalized exploratory well costs that is pending the determination of proved reserves. This does not include amounts that were capitalized and subsequently expensed in the same annual period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447 + Details
Name: | us-gaap_CapitalizedExploratoryWellCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Previously capitalized costs of the drilling of wells that were reclassified as part of the costs of the enterprise's wells and related equipment and facilities at the time that proved reserves were found. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447 + Details
Name: | us-gaap_ReclassificationToWellFacilitiesAndEquipmentBasedOnDeterminationOfProvedReserves
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Dry hole costs from oil and gas producing activities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 360 -Section 25 -Paragraph 9 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6474861&loc=d3e64954-109465 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 23 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62136-109447 + Details
Name: | us-gaap_ResultsOfOperationsDryHoleCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration