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v3.19.1

Condensed Consolidating Financial Information - Additional Information (Details) | 3 Months Ended
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Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract] |
Ownership percentage, guarantors (as percent) | 100.00%

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- Definition Ownership percentage, guarantor + References No definition available. + Details
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Namespace Prefix: | oas_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
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