XML 75 R59.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Acquisitions - Additional Information (Details) (USD $) | 3 Months Ended | 12 Months Ended | 0 Months Ended | 1 Months Ended | 0 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 | Oct. 01, 2013 acre seller | Oct. 31, 2013 | Sep. 26, 2013 acre
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenues | $ 299,672,000 us-gaap_OilAndGasRevenue | $ 368,659,000 us-gaap_OilAndGasRevenue | $ 372,378,000 us-gaap_OilAndGasRevenue | $ 349,519,000 us-gaap_OilAndGasRevenue | $ 333,615,000 us-gaap_OilAndGasRevenue | $ 305,498,000 us-gaap_OilAndGasRevenue | $ 254,582,000 us-gaap_OilAndGasRevenue | $ 248,304,000 us-gaap_OilAndGasRevenue | $ 1,390,228,000 us-gaap_OilAndGasRevenue | $ 1,141,999,000 us-gaap_OilAndGasRevenue | $ 686,668,000 us-gaap_OilAndGasRevenue |  |  |
Operating income | 15,924,000 us-gaap_OperatingIncomeLoss | 134,103,000 us-gaap_OperatingIncomeLoss | 166,545,000 us-gaap_OperatingIncomeLoss | 329,080,000 us-gaap_OperatingIncomeLoss | 122,133,000 us-gaap_OperatingIncomeLoss | 150,862,000 us-gaap_OperatingIncomeLoss | 113,450,000 us-gaap_OperatingIncomeLoss | 117,953,000 us-gaap_OperatingIncomeLoss | 645,652,000 us-gaap_OperatingIncomeLoss | 504,398,000 us-gaap_OperatingIncomeLoss | 276,993,000 us-gaap_OperatingIncomeLoss |  |  |
Capital spending commitment | 4,800,000 oas_CapitalSpendingCommitment |  |  |  |  |  |  |  | 4,800,000 oas_CapitalSpendingCommitment |  |  |  |  |
West Williston Acquisition [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of sellers |  |  |  |  |  |  |  |  |  |  |  | 2 oas_BusinessCombinationNumberofSellers / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember |  |
Acres acquired |  |  |  |  |  |  |  |  |  |  |  | 136,000 oas_BusinessCombinationAcresAcquired / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember |  |
Recognized identifiable assets acquired | 1,475,361,000 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember |  |  |  |  |  |  |  | 1,475,361,000 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  |  |  |  |  | 57,600,000 us-gaap_OilAndGasRevenue / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember |
Operating income |  |  |  |  |  |  |  |  |  |  |  |  | 14,900,000 us-gaap_OperatingIncomeLoss / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember |
Acquisition costs |  |  |  |  |  |  |  |  |  |  |  |  | 2,000,000 us-gaap_BusinessCombinationAcquisitionRelatedCosts / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember |
Consideration transferred |  |  |  |  |  |  |  |  | 1,475,361,000 us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember |  |  |  |  |
East Nesson [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Acres acquired |  |  |  |  |  |  |  |  |  |  |  |  |  | 25,000 oas_BusinessCombinationAcresAcquired / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Recognized identifiable assets acquired | 56,750,000 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember |  |  |  |  |  |  |  | 56,750,000 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember |  |  |  |  |
Consideration transferred |  |  |  |  |  |  |  |  | 56,750,000 us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember |  |  |  |  | 56,800,000 us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember
Capital spending commitment |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 8,200,000 oas_CapitalSpendingCommitment / us-gaap_BusinessAcquisitionAxis = oas_EastNessonMember

X
- Definition Business Combination, Acres Acquired + References No definition available. + Details
Name: | oas_BusinessCombinationAcresAcquired
Namespace Prefix: | oas_
Data Type: | num:areaItemType
Balance Type: | na
Period Type: | duration

X
- Definition Business Combination, Number of Sellers + References No definition available. + Details
Name: | oas_BusinessCombinationNumberofSellers
Namespace Prefix: | oas_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Capital Spending Commitment + References No definition available. + Details
Name: | oas_CapitalSpendingCommitment
Namespace Prefix: | oas_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_BusinessAcquisitionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 23 -URI http://asc.fasb.org/extlink&oid=34752592&loc=d3e1043-128460 + Details
Name: | us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 + Details
Name: | us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Aggregate revenue during the period related to oil and gas business activities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 23 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62136-109447 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62246-109447 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Article 5 + Details
Name: | us-gaap_OilAndGasRevenue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The net result for the period of deducting operating expenses from operating revenues. + References No definition available. + Details
Name: | us-gaap_OperatingIncomeLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=oas_EastNessonMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=oas_WestWillistonAcquisitionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |