Debt Instrument, Convertible, Threshold Percentage of Stock Price to Product of Stock Sale Price and Conversion Rate

No definition available.

Name:	oas_DebtInstrumentConvertibleThresholdPercentageofStockPricetoProductofStockSalePriceandConversionRate
Namespace Prefix:	oas_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of Credit Facility, Maximum Borrowing Capacity, Accordian Feature

+ References

No definition available.

+ Details

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

- Definition

Ownership percentage, guarantor

+ References

No definition available.

+ Details

Name:	oas_OwnershipPercentageGuarantor
Namespace Prefix:	oas_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031898-161870

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionRatio1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instrument must exceed threshold percentage for specified number of trading days to trigger conversion feature.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum percentage of common stock price to conversion price of convertible debt instruments to determine eligibility of conversion.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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+ Details

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

- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

+ Details

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

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
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-Subparagraph (SX 210.5-02.22(a)(1))
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+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

Name:	us-gaap_DebtInstrumentRedemptionPricePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value amount of debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchaseAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchasedFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after accumulated amortization, of debt discount.

+ References

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+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

+ Details

Name:	us-gaap_DeferredFinanceCostsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainsLossesOnExtinguishmentOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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+ Details

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

- Definition

The maximum amount of borrowing capacity under a line of credit that is available as of the balance sheet date for a specific purpose other than for financing goods acquired for inventory or imminent delivery to a customer.

+ References

No definition available.

+ Details

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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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+ Details

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

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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-Paragraph 14
-Subparagraph (b)
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+ Details

Name:	us-gaap_ProceedsFromIssuanceOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt.

+ References

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+ Details

Name:	us-gaap_RepaymentsOfUnsecuredDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

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+ Details

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

- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

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Balance Type:	debit
Period Type:	duration

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- Details

Name:	us-gaap_DebtInstrumentAxis=oas_AmendedCreditFacilityMember
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- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_BridgeLoanMember
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- Details

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- Details

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- Details

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- Details

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Name:	srt_RangeAxis=srt_MaximumMember
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Long-Term Debt - Additional Information (Details)			3 Months Ended		9 Months Ended
Long-Term Debt - Additional Information (Details)	May 29, 2018 USD ($)	May 14, 2018 USD ($)	Sep. 30, 2018 USD ($) $ / shares	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) day $ / shares	Sep. 30, 2017 USD ($)	Oct. 16, 2018 USD ($)	Jun. 30, 2018 USD ($)	May 25, 2018 USD ($)	Apr. 19, 2018 USD ($)	Feb. 26, 2018 USD ($)	Dec. 31, 2017 USD ($)	Apr. 10, 2017 USD ($)	Sep. 30, 2016 USD ($)
Debt Instrument [Line Items]
Total long-term debt			$ 2,633,009,000		$ 2,633,009,000							$ 2,097,606,000
Payment to redeem outstanding notes					423,190,000	$ 0
Loss on extinguishment of debt			(47,000)	$ 0	(13,698,000)	$ 0
Write-off of deferred financing costs					$ 4,000,000
Ownership percentage, guarantors (as percent)					100.00%
Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt, fair value			2,172,300,000		$ 2,172,300,000
Amended Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, remaining borrowing capacity			814,000,000		814,000,000
Swingline Loan [Member] \| The Credit Agreement [Member]
Debt Instrument [Line Items]
Credit facility borrowing base			10,000,000		10,000,000
Line of Credit [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, amount outstanding			14,000,000		14,000,000
Line of Credit [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility amount			$ 2,500,000,000		$ 2,500,000,000
Credit facility borrowing base										$ 1,600,000,000
Line of credit facility, current borrowing capacity										$ 1,350,000,000	$ 1,350,000,000		$ 1,150,000,000
Weighted average interest rate (as percent)			4.00%		4.00%
Line of Credit [Member] \| Revolving Credit Facility [Member] \| Senior Secured Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Long-term debt, gross			$ 522,000,000		$ 522,000,000							70,000,000
Weighted average interest rate (as percent)			3.90%		3.90%
Line of Credit [Member] \| Revolving Credit Facility [Member] \| OMP Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Long-term debt, gross			$ 166,000,000		$ 166,000,000							78,000,000
Credit facility borrowing base			250,000,000		250,000,000			$ 200,000,000
Senior Notes [Member]
Debt Instrument [Line Items]
Debt issuance costs			22,212,000		22,212,000							22,956,000
Long-term debt, gross			2,039,409,000		2,039,409,000							2,052,950,000
Aggregate principal amount repurchased									$ 390,600,000
Debt Instrument, Repurchase Amount									$ 402,000,000
Senior Notes [Member] \| Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Total long-term debt			2,039,400,000		2,039,400,000
Senior Notes [Member] \| 2026 Notes [Member]
Debt Instrument [Line Items]
Stated interest rate (as percent)		6.25%
Net proceeds from debt issuance		$ 394,400,000
Debt issued		$ 400,000,000
Senior Notes [Member] \| Notes [Member]
Debt Instrument [Line Items]
Unsecured debt			$ 1,739,400,000		$ 1,739,400,000
Senior Notes [Member] \| Notes [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Stated interest rate (as percent)			6.25%		6.25%
Senior Notes [Member] \| Notes [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Stated interest rate (as percent)			6.875%		6.875%
Senior Notes [Member] \| 7.25% senior unsecured notes due February 1, 2019 [Member]
Debt Instrument [Line Items]
Long-term debt, gross			$ 0		$ 0							54,275,000
Stated interest rate (as percent)			7.25%		7.25%				7.25%
Debt issued									$ 31,300,000
Payment to redeem outstanding notes	$ 23,000,000
Debt redemption price (percent)	100.00%
Senior Notes [Member] \| 6.50% senior unsecured notes due November 1, 2021 [Member]
Debt Instrument [Line Items]
Long-term debt, gross			$ 71,835,000		$ 71,835,000							395,501,000
Stated interest rate (as percent)			6.50%		6.50%				6.50%
Debt issued									$ 323,700,000
Senior Notes [Member] \| 6.875% senior unsecured notes due March 15, 2022 [Member]
Debt Instrument [Line Items]
Long-term debt, gross			$ 901,480,000		$ 901,480,000							937,080,000
Stated interest rate (as percent)			6.875%		6.875%				6.875%
Debt issued									$ 35,600,000
Senior Notes [Member] \| 6.875% senior unsecured notes due January 15, 2023 [Member]
Debt Instrument [Line Items]
Long-term debt, gross			$ 366,094,000		$ 366,094,000							366,094,000
Stated interest rate (as percent)			6.875%		6.875%
Senior Notes [Member] \| 2.625% senior convertible notes due September 15, 2023 [Member]
Debt Instrument [Line Items]
Debt discount			$ 72,188,000		$ 72,188,000							80,388,000		$ 93,200,000
Long-term debt, gross			$ 300,000,000		$ 300,000,000							$ 300,000,000
Stated interest rate (as percent)			2.625%		2.625%
Debt issued			$ 300,000,000		$ 300,000,000
Debt conversion rate per $1000 principal (in shares per $1000)					0.0763650
Debt conversion price (in dollars per share) \| $ / shares			$ 13.10		$ 13.10
Debt instrument effective interest rate (percent)														8.97%
Estimated fair value of debt														$ 206,800,000
Revolving Credit Facility [Member] \| LIBOR [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Commitment fee percentage			0.375%
Revolving Credit Facility [Member] \| LIBOR [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Commitment fee percentage			0.50%
Debt Conversion Scenario 1 [Member] \| Senior Notes [Member] \| 2.625% senior convertible notes due September 15, 2023 [Member]
Debt Instrument [Line Items]
Number of trading days \| day					20
Number of consecutive trading days \| day					30
Stock price relative to conversion price (percent)					130.00%
Debt Conversion Scenario 2 [Member] \| Senior Notes [Member] \| 2.625% senior convertible notes due September 15, 2023 [Member]
Debt Instrument [Line Items]
Number of trading days \| day					5
Number of consecutive trading days \| day					5
Stock price relative to product of sale price and conversion rate (percent)					98.00%
OMP Operating, LLC [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Credit facility borrowing base			$ 10,000,000		$ 10,000,000
OMP Operating, LLC [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity subject to certain conditions			$ 400,000,000		$ 400,000,000
OMP Operating, LLC [Member] \| Revolving Credit Facility [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Commitment fee percentage					0.375%
OMP Operating, LLC [Member] \| Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Commitment fee percentage					0.50%
OMP Operating, LLC [Member] \| ABR Loans [Member] \| Revolving Credit Facility [Member] \| Federal Funds Effective Swap Rate [Member]
Debt Instrument [Line Items]
Spread on variable rate					0.50%
OMP Operating, LLC [Member] \| ABR Loans [Member] \| Revolving Credit Facility [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Spread on variable rate					1.00%
OMP Operating, LLC [Member] \| Eurodollar Loans [Member] \| Revolving Credit Facility [Member] \| LIBOR [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Spread on variable rate					1.75%
OMP Operating, LLC [Member] \| Eurodollar Loans [Member] \| Revolving Credit Facility [Member] \| LIBOR [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Spread on variable rate					2.75%
OMP Operating, LLC [Member] \| ABR Loans or Swingline Loans [Member] \| Revolving Credit Facility [Member] \| Federal Funds Effective Swap Rate [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Spread on variable rate					0.75%
OMP Operating, LLC [Member] \| ABR Loans or Swingline Loans [Member] \| Revolving Credit Facility [Member] \| Federal Funds Effective Swap Rate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Spread on variable rate					1.75%
OMP Operating, LLC [Member] \| ABR Loans or Swingline Loans [Member] \| Revolving Credit Facility [Member] \| LIBOR [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Spread on variable rate					0.75%
OMP Operating, LLC [Member] \| ABR Loans or Swingline Loans [Member] \| Revolving Credit Facility [Member] \| LIBOR [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Spread on variable rate					1.75%
Subsequent Event [Member] \| Line of Credit [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility amount							$ 3,000,000,000