Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

+ Details

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Namespace Prefix:	invest_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

The aggregate commitment may be increased to this amount by increasing the commitment of one or more lender(s) under the credit facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	oas_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of Financial Institutions

+ References

No definition available.

+ Details

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Namespace Prefix:	oas_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Average fixed price related to the group of price risk swap derivatives.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Details

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- Details

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Namespace Prefix:
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- Details

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Namespace Prefix:
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- Details

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Subsequent Events Subsequent Events (Details) (USD $)	Mar. 31, 2015 financial_institution	Apr. 13, 2015	Apr. 12, 2015	May 07, 2015
Subsequent Event [Line Items]
Number of lenders in the bank group	18oas_NumberofFinancialInstitutions
Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Line of credit facility maximum increase to aggregate commitments	2,000,000,000
Line of credit facility, maximum borrowing capacity	1,500,000,000
Revolving Credit Facility [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Line of credit facility maximum increase to aggregate commitments		1,700,000,000.0	2,000,000,000
Line of credit facility, maximum borrowing capacity		$ 1,525,000,000	$ 1,500,000,000
Not Designated as Hedging Instrument [Member] \| Energy Related Derivative [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Average swap price (in dollars per barrel)				61.28
Two Thousand Fifteen Swap Agreement [Member] \| Not Designated as Hedging Instrument [Member] \| Energy Related Derivative [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Total Notional Amount of Oil (Barrels)				1,102
Two Thousand Sixteen Swap Agreement [Member] \| Not Designated as Hedging Instrument [Member] \| Energy Related Derivative [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Total Notional Amount of Oil (Barrels)				703
Two Thousand Seventeen Swap Agreement [Member] \| Not Designated as Hedging Instrument [Member] \| Energy Related Derivative [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Total Notional Amount of Oil (Barrels)				31