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Acquisitions - Pro Forma (Details) (West Williston Acquisition [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
West Williston Acquisition [Member]
Business Acquisition, Pro Forma Information [Abstract]
Revenues	$ 1,297,545us-gaap_BusinessAcquisitionsProFormaRevenue / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember	$ 831,575us-gaap_BusinessAcquisitionsProFormaRevenue / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember
Net income	$ 231,217us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember	$ 136,004us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss / us-gaap_BusinessAcquisitionAxis = oas_WestWillistonAcquisitionMember

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- Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
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X

- Definition

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(2)-(3)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

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- Definition

The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(2)-(3)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

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