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Acquisitions - Allocation of Purchase Price (Details) (USD $) In Thousands, unless otherwise specified | 0 Months Ended | 12 Months Ended
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Sep. 26, 2013 | Dec. 31, 2014
West Williston Acquisition [Member] |  |
Business Combination, Consideration Transferred [Abstract] |  |
Cash |  | $ 1,475,361 us-gaap_PaymentsToAcquireBusinessesGross / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Forgiveness of debt |  | 0 us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Total consideration |  | 1,475,361 us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract] |  |
Proved developed properties |  | 519,712 oas_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedProvedDevelopedProperties / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Proved undeveloped properties |  | 165,907 oas_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedProvedUndevelopedProperties / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Unproved lease acquisition costs |  | 787,589 oas_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedUnprovedLeaseAcquisitionCosts / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Other property and equipment |  | 13,157 oas_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherPropertyandEquipment / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Inventory |  | 3,181 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Accounts receivable |  | 276 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Total assets acquired |  | 1,489,822 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities [Abstract] |  |
Asset retirement obligations |  | 6,598 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Revenues payable |  | 7,863 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Total liabilities assumed |  | 14,461 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Total identifiable net assets |  | 1,475,361 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
East Nesson [Member] |  |
Business Combination, Consideration Transferred [Abstract] |  |
Cash |  | 56,793 us-gaap_PaymentsToAcquireBusinessesGross / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Forgiveness of debt |  | (43)us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Total consideration | 56,800 us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember | 56,750 us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract] |  |
Proved developed properties |  | 32,053 oas_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedProvedDevelopedProperties / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Proved undeveloped properties |  | 1,807 oas_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedProvedUndevelopedProperties / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Unproved lease acquisition costs |  | 23,369 oas_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedUnprovedLeaseAcquisitionCosts / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Other property and equipment |  | 0 oas_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherPropertyandEquipment / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Inventory |  | 148 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Accounts receivable |  | 0 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Total assets acquired |  | 57,377 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities [Abstract] |  |
Asset retirement obligations |  | 307 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Revenues payable |  | 320 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Total liabilities assumed |  | 627 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Total identifiable net assets |  | $ 56,750 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember

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- Definition Amount due from customers or clients for goods or services, including trade receivables, that have been delivered or sold in the normal course of business, and amounts due from others, including related parties expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 + Details
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- Definition The amount of inventory recognized as of the acquisition date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 55 -Paragraph 37 -URI http://asc.fasb.org/extlink&oid=35744172&loc=d3e2207-128464 + Details
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- Definition Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 55 -Paragraph 37 -URI http://asc.fasb.org/extlink&oid=35744172&loc=d3e2207-128464 + Details
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