Black Stone Minerals (BSM) 10-Q 5 Jun 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	29-May-15
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Trading Symbol	BSM
Entity Registrant Name	Black Stone Minerals, L.P.
Entity Central Index Key	1621434
Current Fiscal Year End Date	-19
Entity Filer Category	Non-accelerated Filer
Common Units
Document Information [Line Items]
Entity Partnership Units Outstanding		96,177,147
Subordinate Units
Document Information [Line Items]
Entity Partnership Units Outstanding		95,057,312
Preferred Units
Document Information [Line Items]
Entity Partnership Units Outstanding		117,963

CONSOLIDATED_BALANCE_SHEETS_Un

CONSOLIDATED BALANCE SHEETS (Unaudited) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
CURRENT ASSETS
Cash and cash equivalents	$8,368	$14,803
Accounts receivable	50,794	74,092
Commodity derivative assets	38,913	37,471
Prepaid expenses and other current assets	10,523	8,538
TOTAL CURRENT ASSETS	108,598	134,904
PROPERTY AND EQUIPMENT
Oil and natural gas properties, at cost, on the basis of the successful efforts method of accounting, includes unproved properties of $625,392 and $626,376 at March 31, 2015 and December 31, 2014, respectively	2,394,096	2,379,543
Accumulated depreciation, depletion and amortization, including impairment	-1,232,584	-1,191,861
Oil and natural gas properties, net	1,161,512	1,187,682
Other property and equipment, net of accumulated depreciation of $13,558 and $12,994 at March 31, 2015 and December 31, 2014, respectively	1,098	1,664
NET PROPERTY AND EQUIPMENT	1,162,610	1,189,346
DEFERRED CHARGES AND OTHER LONG-TERM ASSETS	3,083	2,532
TOTAL ASSETS	1,274,291	1,326,782
CURRENT LIABILITIES
Accounts payable	31,080	29,415
Accrued liabilities	12,165	16,252
Accrued partners' distribution payable	52,724	52,905
TOTAL CURRENT LIABILITIES	95,969	98,572
LONG-TERM LIABILITIES
Credit facilities	389,000	394,000
Accrued incentive compensation	3,714	6,530
Commodity derivative liabilities	37
Deferred revenue	3,813	3,917
Asset retirement obligations	9,621	9,381
TOTAL LIABILITIES	502,154	512,400
COMMITMENTS AND CONTINGENCIES (Note 7)
MEZZANINE EQUITY
Partners' equity - redeemable preferred units, 118 and 157 units outstanding at March 31, 2015 and December 31, 2014, respectively	120,889	161,165
EQUITY
Partners' equity - common limited partner units, 167,767 and 164,484 units outstanding at March 31, 2015 and December 31, 2014, respectively	648,672	650,598
Noncontrolling interests	2,576	2,619
TOTAL EQUITY	651,248	653,217
TOTAL LIABILITIES, MEZZANINE EQUITY AND EQUITY	$1,274,291	$1,326,782

CONSOLIDATED_BALANCE_SHEETS_Un1

CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, except Share data, unless otherwise specified
Oil and natural gas properties, unproved property costs	$625,392	$626,376
Other property and equipment accumulated depreciation and amortization	$13,558	$12,994
Preferred Units
Partners' equity, preferred units, outstanding	117,980	157,203
Common Units
Partners' equity, common units, outstanding	167,767,000	164,484,000

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
REVENUE
Oil and condensate sales	$36,163	$59,642
Natural gas and natural gas liquids sales	31,640	58,206
Gain (loss) on commodity derivative instruments	19,647	-5,995
Lease bonus and other income	3,611	15,559
TOTAL REVENUE	91,061	127,412
OPERATING (INCOME) EXPENSE
Lease operating expenses and other	6,172	4,869
Production costs and ad valorem taxes	8,256	10,586
Depreciation, depletion and amortization	27,891	23,134
Impairment of oil and natural gas properties	13,467
General and administrative	14,818	15,451
Accretion of asset retirement obligations	271	147
Gain on sale of assets	-7
TOTAL OPERATING EXPENSE	70,868	54,187
INCOME FROM OPERATIONS	20,193	73,225
OTHER INCOME (EXPENSE)
Interest and investment income	1	22
Interest expense	-2,945	-3,433
Other income	50	70
TOTAL OTHER EXPENSE	-2,894	-3,341
NET INCOME	17,299	69,884
NET (INCOME) LOSS ATTRIBUTABLE TO NONCONTROLLING INTERESTS	-9	3
DIVIDENDS ON PREFERRED UNITS	-2,909	-3,882
NET INCOME ATTRIBUTABLE TO THE GENERAL PARTNER AND LIMITED PARTNERS	14,381	66,005
ALLOCATION OF NET INCOME ATTRIBUTABLE TO:
Common limited partner interest	14,381	66,005
NET INCOME ATTRIBUTABLE TO THE GENERAL PARTNER AND LIMITED PARTNERS	$14,381	$66,005
Common Units
NET INCOME ATTRIBUTABLE TO LIMITED PARTNERS PER UNIT:
Per common limited partner unit (basic)	$0.09	$0.40
Per common limited partner unit (diluted)	$0.09	$0.40
Weighted average common limited partner units outstanding (basic and diluted)	167,452	164,585

CONSOLIDATED_STATEMENT_OF_EQUI

CONSOLIDATED STATEMENT OF EQUITY (Unaudited) (USD $)	Total	Common Units	Partners Equity Common Units	Noncontrolling Interest
In Thousands	USD ($)		USD ($)	USD ($)
Beginning balance at Dec. 31, 2014	$653,217		$650,598	$2,619
Beginning balance, units at Dec. 31, 2014		164,484
Conversion of redeemable preferred units	39,223		39,223
Conversion of preferred units, units		2,749
Restricted common units granted		562
Repurchase of common units	-523		-523
Repurchase of common units, units		-28
Equity-based compensation	1,243		1,243
Distributions	-56,302		-56,250	-52
Net income	17,299		17,290	9
Dividends on preferred units	-2,909		-2,909
Ending balance at Mar. 31, 2015	$651,248		$648,672	$2,576
Ending balance, units at Mar. 31, 2015		167,767

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$17,299	$69,884
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	27,891	23,134
Impairment of oil and natural gas properties	13,467
Accretion of asset retirement obligations	271	147
Amortization of deferred charges	241	241
(Gain) loss on commodity derivative instruments	-19,647	5,995
Net cash received (paid) on settlement of commodity derivative instruments	17,450	-2,084
Equity-based compensation	1,243	3,499
Gain on disposal of assets	-7
Changes in operating assets and liabilities:
Accounts receivable	23,298	-16,882
Prepaid expenses and other current assets	-365	-333
Accounts payable and accrued liabilities	-6,620	-6,914
Deferred revenue	-104	-2,516
Settlement of asset retirement obligations	-58	-8
NET CASH PROVIDED BY OPERATING ACTIVITIES	74,359	74,163
CASH FLOWS FROM INVESTING ACTIVITIES
Additions to oil and natural gas properties	-13,612	-13,966
Purchase of other property and equipment		-60
Proceeds from the sale of oil and natural gas properties	406	5,439
Acquisitions of oil and natural gas properties		-29,431
NET CASH USED IN INVESTING ACTIVITIES	-13,206	-38,018
CASH FLOWS FROM FINANCING ACTIVITIES
Distributions to common equity owners	-56,483	-55,517
Repurchase of common equity units	-523	-406
Dividends on preferred units	-3,962	-3,968
Net (repayments) borrowings under senior line of credit	-5,000	11,500
Note receivable-officers		101
Payments incurred for initial public offering	-1,620
NET CASH USED IN FINANCING ACTIVITIES	-67,588	-48,290
NET CHANGE IN CASH AND CASH EQUIVALENTS	-6,435	-12,145
CASH AND CASH EQUIVALENTS - beginning of the period	14,803	30,123
CASH AND CASH EQUIVALENTS - end of the period	8,368	17,978
SUPPLEMENTAL DISCLOSURE
Interest paid	2,664	3,187
NON-CASH ACTIVITIES
Property additions financed through accounts payable and accrued liabilities	15,512	23,332
Liabilities assumed as consideration for oil and natural gas properties acquired		7,000
Deferred revenue settled through acquisition of oil and natural gas properties		-2,657
Asset retirement obligations incurred	27	31
Accrued distributions payable	-181	806
Conversion of redeemable preferred units	($39,223)

Business_and_Basis_of_Presenta

Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Business and Basis of Presentation	NOTE 1—BUSINESS AND BASIS OF PRESENTATION
	Description of the business: Black Stone Minerals Company, L.P., a Delaware limited partnership, and its subsidiaries (collectively referred to as “BSMC” or the “Predecessor”) own oil and natural gas mineral interests in the United States (“U.S.”). Black Stone Minerals, L.P. (“BSM”) is a publicly traded Delaware limited partnership formed on September 16, 2014. On May 6, 2015, BSM completed its initial public offering (the “IPO”) of 22,500,000 common units representing limited partner interests at a price to the public of $19.00 per common unit. BSM received proceeds of $391.6 million from the sale of its common units, net of underwriting discount, structuring fee, and estimated offering expenses (including costs previously incurred and capitalized). BSM used the net proceeds from the IPO to repay substantially all indebtedness outstanding under its credit facility. On May 1, 2015, BSM’s common units began trading on the New York Stock Exchange under the symbol “BSM.”
	In connection with the IPO, BSMC was merged into a wholly owned subsidiary of BSM, with BSMC as the surviving entity. Pursuant to the merger, the Class A and Class B common units representing limited partner interests of the Predecessor were converted into an aggregate of 72,574,715 common units and 95,057,312 subordinated units of BSM at a conversion ratio of 12.9465:1 for 0.4329 common units and 0.5671 subordinated units, and the preferred units of BSMC were converted into an aggregate of 117,963 preferred units of BSM at a conversion ratio of one to one. The merger is accounted for as a combination of entities under common control with assets and liabilities transferred at their carrying amounts in a manner similar to a pooling of interests. Unless otherwise stated or the context otherwise indicates, all references to the “Company” or similar expressions for time periods prior to the IPO refer to Black Stone Minerals Company, L.P. and its subsidiaries, the Predecessor, for accounting purposes. For time periods subsequent to the IPO, these terms refer to Black Stone Minerals, L.P. and its subsidiaries.
	In addition to mineral interests, the Company’s assets include nonparticipating and overriding royalty interests. These non-cost-bearing interests are collectively referred to as “mineral and royalty interests.” As of March 31, 2015, the Company’s mineral and royalty interests are located in most of the major onshore oil and natural gas producing basins spread across 41 states and 62 onshore oil and natural gas producing basins of the continental U.S. The Company also owns non-operated working interests in certain oil and natural gas properties.
	Basis of presentation: The accompanying unaudited interim consolidated financial statements of the Company have been prepared in accordance with generally accepted accounting principles (“GAAP”) in the U.S. and pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). These unaudited interim consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and, therefore, do not include all disclosures required for financial statements prepared in conformity with U.S. GAAP. Accordingly, the accompanying unaudited interim consolidated financial statements and related notes should be read in conjunction with the Company’s annual consolidated financial statements and related notes included in its final prospectus (the “Prospectus”) dated April 30, 2015 and filed with the SEC, pursuant to Rule 424(b) under the Securities Act of 1933 (the “Securities Act”), on May 1, 2015. Certain reclassifications have been made to the prior periods presented to conform to the current period financial statement presentation. The reclassifications have no effect on the consolidated financial position, results of operations, or cash flows of the Company. In the opinion of management, all material adjustments, which are of a normal and recurring nature, necessary for a fair presentation of the results for the periods presented have been reflected. The results of operations for the three months ended March 31, 2015 are not necessarily indicative of the results to be expected for the full year.
	The Company evaluates significant terms of its investments to determine the method of accounting applied to the investments. Investments in which the Company has less than a 20% ownership interest and does not have control or exercise significant influence are accounted for under the cost method. The Company’s cost method investment is included in deferred charges and other long-term assets in the consolidated balance sheets. Investments in which the Company exercises control are consolidated, and the noncontrolling interests of such investments, which are not attributable directly or indirectly to the Company, are presented as a separate component of net income and equity in the accompanying consolidated financial statements.
	The consolidated financial statements include undivided interests in oil and natural gas property rights. The Company accounts for its share of oil and natural gas property rights by reporting its proportionate share of assets, liabilities, revenues, costs and cash flows within the relevant lines on the accompanying consolidated balance sheets, statements of operations, and cash flow statements.
	Segment reporting: The Company operates in a single operating and reportable segment. Operating segments are defined as components of an enterprise for which separate financial information is evaluated regularly by the chief operating decision maker in deciding how to allocate resources and assess performance. The Company’s chief executive officer has been determined to be the chief operating decision maker and allocates resources and assesses performance based upon financial information at the consolidated level.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE 2—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	Significant accounting policies: Our significant accounting policies are disclosed in Note 2 of the consolidated financial statements for the years ended December 31, 2014 and 2013 included in the Prospectus. There have been no changes in such policies or the application of such policies during the quarter ended March 31, 2015.
	New accounting pronouncements: In May 2014, the Financial Accounting Standards Board (the “FASB”) issued an accounting standards update on a comprehensive new revenue recognition standard that will supersede Accounting Standards Codification (“ASC”) 605, Revenue Recognition. The new accounting guidance creates a framework under which an entity will allocate the transaction price to separate performance obligations and recognize revenue when each performance obligation is satisfied. Under the new standard, entities will be required to use judgment and make estimates, including identifying performance obligations in a contract, estimating the amount of variable consideration to include in the transaction price, allocating the transaction price to each separate performance obligation and determining when an entity satisfies its performance obligations. The standard allows for either “full retrospective” adoption, meaning that the standard is applied to all of the periods presented with a cumulative catch-up as of the earliest period presented, or “modified retrospective” adoption, meaning the standard is applied only to the most current period presented in the financial statements with a cumulative catch-up as of the current period. The accounting standard will be effective for reporting periods beginning after December 15, 2016 for public companies. However, in April 2015, the FASB tentatively decided to defer the effective date by one year to be effective for annual reporting periods beginning after December 15, 2017. The Company is evaluating the impact that the new accounting guidance will have on its consolidated financial position, results of operations, and cash flows and has not yet determined the method by which it will adopt the standard.
	In April 2015, the FASB issued an accounting standards update that requires debt issuance costs related to a recognized debt liability to be presented in the balance sheet as a direct deduction from the carrying value of that debt liability, consistent with debt discounts. The guidance is effective retrospectively for fiscal years, and interim periods within those years, beginning after December 15, 2015. Early adoption is permitted for financial statements that have not been previously issued. The Company does not expect the impact of adopting this guidance will be material to the Company’s consolidated financial statements and related disclosures.
	In April 2015, the FASB issued an accounting standards update that specifies that for purposes of calculating historical earnings per unit under the two-class method, the earnings (losses) of a transferred business before the date of a dropdown transaction should be allocated entirely to the general partner. In that circumstance, the previously reported earnings per unit of the limited partners (which is typically the earnings per unit measure presented in the financial statements) would not change as a result of the dropdown transaction. Qualitative disclosures about how the rights to the earnings (losses) differ before and after the dropdown transaction occurs for purposes of computing earnings per unit under the two-class method also are required.  The guidance is effective retrospectively for fiscal years, and interim periods within those years, beginning after December 15, 2015. Early adoption is permitted. The Company does not expect the impact of adopting this guidance will be material to the Company’s consolidated financial statements and related disclosures.

Asset_Retirement_Obligations

Asset Retirement Obligations	3 Months Ended
	Mar. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	NOTE 3—ASSET RETIREMENT OBLIGATIONS
	The asset retirement obligation (“ARO”) liability reflects the present value of estimated costs of dismantlement, removal, site reclamation, and similar activities associated with the Company’s oil and natural gas properties. The Company utilizes current retirement costs to estimate the expected cash outflows for retirement obligations. The Company estimates the ultimate productive life of its properties, a risk-adjusted discount rate, and an inflation factor in order to determine the current present value of this obligation. To the extent future revisions to these assumptions impact the present value of the existing ARO liability, a corresponding adjustment is made to the oil and natural gas property balance. The following table describes changes to the Company’s ARO liability during the period:
		For the three months ended
		31-Mar-15
		(In thousands)
	Beginning asset retirement obligations	$	9,381
	Liabilities incurred		27
	Liabilities settled		(58	)
	Accretion expense		271
	Ending asset retirement obligations	$	9,621

Derivatives_and_Financial_Inst

Derivatives and Financial Instruments	3 Months Ended
	Mar. 31, 2015
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivatives and Financial Instruments	NOTE 4—DERIVATIVES AND FINANCIAL INSTRUMENTS
	The Company’s ongoing operations expose it to changes in the market price for oil and natural gas. To mitigate the given commodity price risk associated with its operations, the Company uses derivative instruments. From time to time, such instruments may include fixed-price contracts, variable to fixed-price swaps, costless collars, and other contractual arrangements. The Company does not enter into derivative instruments for speculative purposes.
	Costless collars are a combination of a purchased put option and a sold call option, in which the premiums net to zero. With a costless collar, the counterparty is required to make a payment to the Company if the settlement price for any settlement period is below the exercise price of the purchased put. The Company is required to make a payment to the counterparty if the settlement price for any settlement period is above the exercise price for the sold call of the collar. The settlement paid or received is the difference between the market price on the settlement date and the related exercise price. The Company has also entered into commodity derivative instruments in the form of fixed price swap contracts. A fixed price swap contract between the Company and a counterparty specifies a fixed commodity price and a future settlement date. The Company will receive from, or pay to, the counterparty the difference between the fixed swap price and the market price on the settlement date. All derivative instruments that have not yet been settled in cash are reflected as either assets or liabilities in the Company’s accompanying consolidated balance sheets as of March 31, 2015 and December 31, 2014. See Note 5 – Fair Value Measurement for further discussion.
	The table below summarizes the fair value and classification of the Company’s derivative instruments:
	As of March 31, 2015
	(In thousands)
	Classification	Balance Sheet Location		Gross Fair				Effect of				Net Carrying
				Value				Counterparty				Value on
								Netting				Balance Sheet
	Assets:
	Current asset	Commodity derivative assets		$	39,055			$	(142	)		$	38,913
	Non-current asset	Deferred charges and other long-term assets			992				(200	)			792
	Total assets			$	40,047			$	(342	)		$	39,705
	Liabilities:
	Current liability	Commodity derivative liabilities		$	142			$	(142	)		$	—
	Non-current liability	Commodity derivative liabilities			237				(200	)			37
	Total liabilities			$	379			$	(342	)		$	37
	As of December 31, 2014
	(In thousands)
	Classification	Balance Sheet Location		Gross Fair				Effect of				Net Carrying
				Value				Counterparty				Value on
								Netting				Balance Sheet
	Assets:
	Current asset	Commodity derivative assets		$	37,656			$	(185	)		$	37,471
	Non-current asset	Deferred charges and other long-term assets			—				—				—
	Total assets			$	37,656			$	(185	)		$	37,471
	Liabilities:
	Current liability	Commodity derivative liability		$	185			$	(185	)		$	—
	Non-current liability	Commodity derivative liability			—				—				—
	Total liabilities			$	185			$	(185	)		$	—
	Changes in the fair values of the Company’s derivative instruments (both assets and liabilities) are presented on a net basis in the accompanying consolidated statements of operations. Changes in the fair value of the Company’s commodity derivative instruments (both assets and liabilities) are as follows:
		For the three months ended March 31,
	Derivatives not designated as hedging instruments under ASC 815	2015				2014
		(In thousands)
	Beginning fair value of commodity derivative instruments	$	37,471			$	(1,812	)
	Gain (loss) on oil derivative instruments		13,019				(1,551	)
	Gain (loss) on natural gas derivative instruments		6,628				(4,444	)
	Net cash (received) paid on settlements of oil derivative		(11,509	)			18
	instruments
	Net cash (received) paid on settlements of natural gas		(5,941	)			2,066
	derivative instruments
	Net change in fair value of commodity derivative		2,197				(3,911	)
	instruments
	Ending fair value of commodity derivative instruments	$	39,668			$	(5,723	)
	The Company had the following open derivative contracts for oil as of March 31, 2015:
		Volume				Weighted Average				Range (Per Bbl)
	Period and Type of Contract	(Bbl)				(Per Bbl)				Low				High
	Oil Collars:
	2015
	Collar contracts:
	Call Options		625,000			$	102.02			$	99.05			$	104
	Put Options		625,000			$	84.88			$	80			$	90
	Oil Swaps:
	2015
	Swap contracts:		1,106,000			$	58.71			$	52.05			$	61.71
	2016
	Swap contracts:		1,540,000			$	57.98			$	54.8			$	60.41
	The Company had the following open derivative contracts for natural gas as of March 31, 2015:
		Volume				Weighted Average				Range (Per MMBtu)
	Period and Type of Contract	(MMBtu)				(Per MMBtu)				Low				High
	Natural Gas Collars:
	2015
	Collar contracts:
	Call Options		3,640,000			$	4.82			$	4.51			$	5.13
Put Options		3,640,000			$	3.81			$	3.5			$	4
Natural Gas Swaps:
2015
Swap contracts:		18,580,000			$	3.12			$	2.72			$	3.53
2016
Swap contracts:		22,450,000			$	3.18			$	3.03			$	3.41

Fair_Value_Measurement

Fair Value Measurement	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	NOTE 5—FAIR VALUE MEASUREMENT
	ASC 820, Fair Value Measurement, defines fair value as the amount at which an asset (or liability) could be bought (or incurred) or sold (or settled) in an orderly transaction between market participants at the measurement date. Further, ASC 820 establishes a framework for measuring fair value, establishes a fair value hierarchy based on the quality of inputs used to measure fair value, and includes certain disclosure requirements. Fair value estimates are based on either (i) actual market data or (ii) assumptions that other market participants would use in pricing an asset or liability, including estimates of risk.
	ASC 820 establishes a three-level valuation hierarchy for disclosure of fair value measurements. The valuation hierarchy categorizes assets and liabilities measured at fair value into one of three different levels depending on the observability of the inputs employed in the measurement. The three levels are defined as follows:
	Level 1—Unadjusted quoted prices for identical assets or liabilities in active markets.
	Level 2—Quoted prices for similar assets or liabilities in non-active markets, and inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the financial instrument.
	Level 3—Inputs that are unobservable and significant to the fair value measurement (including the Company’s own assumptions in determining fair value).
	A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability. There were no transfers into, or out of, the three levels of the fair value hierarchy for the three months ended March 31, 2015 or the year ended December 31, 2014.
	Fair Value on a Recurring Basis
	The Company estimated the fair value of derivative instruments using the market approach via a model that uses inputs that are observable in the market or can be derived from, or corroborated by, observable data. See Note 4 – Derivatives and Financial Instruments for further discussion.
	The following table presents information about the Company’s assets and liabilities measured at fair value on a recurring basis:
		Fair Value Measurements Using						Effect of
								Counterparty
		Level 1		Level 2		Level 3		Netting			Total
		(In thousands)
	As of March 31, 2015
	Financial Assets
	Commodity derivative instruments	$	—	$	40,047	$	—	$	(342	)	$	39,705
	Financial Liabilities
	Commodity derivative instruments		—		379		—		(342	)	$	37
	As of December 31, 2014
	Financial Assets
	Commodity derivative instruments	$	—	$	37,656	$	—	$	(185	)	$	37,471
	Financial Liabilities
	Commodity derivative instruments		—		185		—		(185	)	$	—
	Fair Value on a Non-Recurring Basis
	The determination of the fair values of proved and unproved properties acquired in purchase transactions are prepared by estimating discounted cash flow projections. The factors used to determine fair value include estimates of economic reserves, future operating and development costs, future commodity prices, and a market-based weighted average cost of capital.
	Oil and natural gas properties are measured at fair value on a nonrecurring basis using the income approach. Proved and unproved oil and natural gas properties are reviewed for impairment when events and circumstances indicate a possible decline in the recoverability of the carrying value of those properties. Significant Level 3 assumptions used to determine fair value include estimates of proved reserves, future commodity prices, the timing and amount of future production and capital expenditures, and a discount rate commensurate with the risk associated with the respective oil and natural gas properties.
	The Company’s estimates of fair value have been determined at discrete points in time based on relevant market data. These estimates involve uncertainty and cannot be determined with precision. There were no significant changes in valuation techniques or related inputs as of March 31, 2015 or December 31, 2014.
	The following table presents information about the Company’s assets measured at fair value on a non-recurring basis:
		Fair Value Measurements Using						Net Book			Impairment
		Level 1		Level 2		Level 3		Value			Loss
		(In thousands)
	As of March 31, 2015
	Impaired oil and natural gas properties	$	—	$	—	$	17,826	$	31,293		$	13,467
	As of December 31, 2014
	Impaired oil and natural gas properties	$	—	$	—	$	81,864	$	199,794		$	117,930
	The estimated fair value of all debt as of March 31, 2015 and December 31, 2014 approximated the carrying value. These fair values, which are Level 3 measurements, were estimated based on the Company’s incremental borrowing rates for similar types of borrowing arrangements, when quoted market prices were not available. The estimated fair values of the Company’s financial instruments are not necessarily indicative of the amounts that would be realized in a current market exchange.

Related_Party_Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2015
Related Party Transactions [Abstract]
Related Party Transactions	NOTE 6—RELATED PARTY TRANSACTIONS
	The Company executed promissory notes dated April 15, 2010, in the amount of $0.5 million to officers of the Company. The promissory notes related to the acquisition of a partnership interest in a former affiliate by the officers, and the notes were collateralized by a security interest in the Company. The aggregate outstanding note balance and interest receivable of $0.1 million was received during the quarter ended March 31, 2014.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 7—COMMITMENTS AND CONTINGENCIES
	Environmental Matters
	The Company’s business includes activities that are subject to U.S. federal, state, and local environmental regulations with regard to air, land, and water quality and other environmental matters.
	The Company does not consider the estimated remediation costs that could result from any environmental site assessments to be significant to the consolidated balance sheet or statement of operations of the Company. No provision for potential remediation costs is reflected in the consolidated financial statements.
	Litigation
	From time to time, the Company is involved in legal actions and claims arising in the ordinary course of business. The Company believes these claims will be resolved without material adverse effect to the Company’s consolidated balance sheet, statement of operations or cash flows.

Credit_Facility

Credit Facility	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Credit Facility	NOTE 8—CREDIT FACILITY
	In September 2006, the Company entered into a credit agreement (the “Senior Line of Credit”) with a syndicate of lenders. During the first quarter of 2012, the Senior Line of Credit was amended to extend the term of the facility to February 3, 2017, at which time all unpaid principal and interest is due. On June 28, 2013, the terms of the Senior Line of Credit were amended to increase the maximum credit amount from the original $600.0 million to $1.0 billion. The borrowing base was $700.0 million at both March 31, 2015 and December 31, 2014, respectively. Our semi-annual borrowing base redetermination process resulted in a decrease of the borrowing base to $600.0 million, effective April 10, 2015. The borrowing base is based on the value of the Company’s oil and natural gas properties. Proceeds from the Senior Line of Credit are used for the acquisition of oil and natural gas properties and for other general business purposes.
	On January 23, 2015, the Senior Line of Credit was amended and restated. Borrowings under the Senior Line of Credit bear interest at LIBOR plus a margin between 1.50% and 2.50%, or prime rate plus a margin between 0.50% and 1.50%, with the margin depending on the borrowing base utilization percentage of the loan. The prime rate is determined to be the higher of the financial institution’s prime rate or the federal funds effective rate plus 0.50% per annum. The weighted average interest rate of the Senior Line of Credit was 2.18% and 2.41% as of March 31, 2015 and December 31, 2014, respectively. Accrued interest is payable at the end of each calendar quarter or at the end of each interest period, unless the interest period is longer than 90 days in which case interest is payable at the end of every 90-day period. In addition, a commitment fee is payable at the end of each calendar quarter based on either a rate of 0.375% if the borrowing base utilization percentage is less than 50%, or 0.50% per annum if the borrowing base utilization percentage is equal to or greater than 50%. The Senior Line of Credit is secured by a majority of the Company’s oil and natural gas production and assets.
	The Senior Line of Credit contains various restrictions on future borrowings, leases and sales of assets. Additionally, the Senior Line of Credit requires the Company to maintain a current ratio of not less than 1.0:1.0 and a ratio of total debt to EBITDAX (Earnings before Interest, Taxes, Depreciation, Amortization, and Exploration) of not more than 3.5:1.0. As of March 31, 2015, the Company was in compliance with all financial covenants in the Senior Line of Credit.
	The aggregate principal balance outstanding was $389.0 million and $394.0 million at March 31, 2015 and December 31, 2014, respectively. The unused portion of the available borrowings under the Senior Line of Credit was $311.0 million and $306.0 million at March 31, 2015 and December 31, 2014, respectively. Refer to Note 1 – Business and Basis of Presentation for discussion of the use of proceeds from the IPO that occurred subsequent to March 31, 2015.

Redeemable_Preferred_Units

Redeemable Preferred Units	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Redeemable Preferred Units	NOTE 9—REDEEMABLE PREFERRED UNITS
	The Company has 117,980 and 157,203 preferred units outstanding with a book value of $120.9 million and $161.2 million as of March 31, 2015 and December 31, 2014, respectively, which includes accrued and unpaid dividends of $2.9 million and $4.0 million as of March 31, 2015 and December 31, 2014, respectively. The preferred units are classified as mezzanine equity on the consolidated balance sheets since redemption is outside the control of the Company. The preferred units are entitled to an annual dividend coupon of 10% of the funded capital of the preferred units payable on a quarterly basis in arrears. The Company accrued dividends on the preferred units of $2.9 million and $3.9 million for the quarters ended March 31, 2015 and 2014, respectively.
	The preferred units are convertible into common units at any time at the option of the preferred unitholders. The preferred units have an adjusted initial conversion price of $14.2683 and an adjusted initial conversion rate of 70.0858 common units per preferred unit, which reflects the reverse split described in Note 1 – Business and Basis of Presentation but does not give pro forma effect to the capital restructuring related to the IPO. In the event the preferred unitholders have not converted all of the preferred units by December 31, 2014, the owners of the preferred units can elect to have the Company redeem up to 25% per year of its preferred units at face value, plus any accrued and unpaid dividends, on December 31 of each year from 2014 to 2017. The Company shall have the right, at its sole option, to redeem an amount of preferred units equal to the units being redeemed by an owner of preferred units on each December 31. Any amount of a given year’s 25% of preferred units not redeemed on December 31 shall automatically convert to common units on January 1 of the following year. On January 1, 2015 and during the quarter ended March 31, 2015, 39,223 preferred units totaling $39.2 million were automatically converted into 2,748,974 common units. No preferred units were converted into common units during the quarter ended March 31, 2014.

Earnings_Per_Unit

Earnings Per Unit	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Unit	NOTE 10—EARNINGS PER UNIT
	Class A and Class B common units have been combined as a single class for purposes of basic and diluted earnings per unit (“EPU”) as they contain the same economic rights and preferences. The holders of the Company’s restricted common units have all the rights of a unitholder, including non-forfeitable distribution rights. As participating securities, the restricted common units are included in the calculation of basic earnings per unit using the two-class method. For the periods presented, the amount of earnings allocated to the participating restricted common units was not material. The redeemable preferred units can be converted into 8.3 million common units and 11.0 million common units as of March 31, 2015 and 2014, respectively. At March 31, 2015 and 2014, if the redeemable preferred units were converted to common units, their effect would be anti-dilutive. Therefore, the redeemable preferred units are not included in the diluted EPU calculation. The following table reflects the retrospective application of the reverse split described in Note 1 – Business and Basis of Presentation but does not give pro forma effect to the capital restructuring related to the IPO.
	The following table sets forth the computation of basic and diluted earnings per unit:
		Three Months Ended March 31,
		2015			2014
		(In thousands, except per unit
		amounts)
	Net income	$	17,299		$	69,884
	Net (income) loss attributable to noncontrolling interests		(9	)		3
	Dividends on preferred units		(2,909	)		(3,882	)
	Net income attributable to the general partner and	$	14,381		$	66,005
	limited partners
	Allocation of net income attributable to:
	General partner interest	$	—		$	—
	Common limited partner interest		14,381			66,005
		$	14,381		$	66,005
	Net income attributable to limited partners per unit:
	Per common limited partner unit (basic and diluted)	$	0.09		$	0.4
	Weighted average common limited partner units outstanding (basic and diluted)		167,452			164,585

Subsequent_Events

Subsequent Events	3 Months Ended
	Mar. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	NOTE 11—SUBSEQUENT EVENTS
	On April 10, 2015, the borrowing base for the Company’s senior line of credit was redetermined and set at $600.0 million by the lenders.
	On April 14, 2015, the Company paid distributions totaling $56.3 million to the holders of common units and $2.9 million to the holders of the Preferred Units.
	On May 6, 2015, the Company completed its initial public offering of 22,500,000 common units representing limited partner interests at a price to the public of $19.00 per common unit. See Note 1 – Business and Basis of Presentation for further discussion of the IPO and related transactions.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
New Accounting Pronouncements	New accounting pronouncements: In May 2014, the Financial Accounting Standards Board (the “FASB”) issued an accounting standards update on a comprehensive new revenue recognition standard that will supersede Accounting Standards Codification (“ASC”) 605, Revenue Recognition. The new accounting guidance creates a framework under which an entity will allocate the transaction price to separate performance obligations and recognize revenue when each performance obligation is satisfied. Under the new standard, entities will be required to use judgment and make estimates, including identifying performance obligations in a contract, estimating the amount of variable consideration to include in the transaction price, allocating the transaction price to each separate performance obligation and determining when an entity satisfies its performance obligations. The standard allows for either “full retrospective” adoption, meaning that the standard is applied to all of the periods presented with a cumulative catch-up as of the earliest period presented, or “modified retrospective” adoption, meaning the standard is applied only to the most current period presented in the financial statements with a cumulative catch-up as of the current period. The accounting standard will be effective for reporting periods beginning after December 15, 2016 for public companies. However, in April 2015, the FASB tentatively decided to defer the effective date by one year to be effective for annual reporting periods beginning after December 15, 2017. The Company is evaluating the impact that the new accounting guidance will have on its consolidated financial position, results of operations, and cash flows and has not yet determined the method by which it will adopt the standard.
	In April 2015, the FASB issued an accounting standards update that requires debt issuance costs related to a recognized debt liability to be presented in the balance sheet as a direct deduction from the carrying value of that debt liability, consistent with debt discounts. The guidance is effective retrospectively for fiscal years, and interim periods within those years, beginning after December 15, 2015. Early adoption is permitted for financial statements that have not been previously issued. The Company does not expect the impact of adopting this guidance will be material to the Company’s consolidated financial statements and related disclosures.
	In April 2015, the FASB issued an accounting standards update that specifies that for purposes of calculating historical earnings per unit under the two-class method, the earnings (losses) of a transferred business before the date of a dropdown transaction should be allocated entirely to the general partner. In that circumstance, the previously reported earnings per unit of the limited partners (which is typically the earnings per unit measure presented in the financial statements) would not change as a result of the dropdown transaction. Qualitative disclosures about how the rights to the earnings (losses) differ before and after the dropdown transaction occurs for purposes of computing earnings per unit under the two-class method also are required.  The guidance is effective retrospectively for fiscal years, and interim periods within those years, beginning after December 15, 2015. Early adoption is permitted. The Company does not expect the impact of adopting this guidance will be material to the Company’s consolidated financial statements and related disclosures.

Asset_Retirement_Obligations_T

Asset Retirement Obligations (Tables)	3 Months Ended
	Mar. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]
Schedule of Change in Asset Retirement Obligation Liability	The following table describes changes to the Company’s ARO liability during the period:
		For the three months ended
		31-Mar-15
		(In thousands)
	Beginning asset retirement obligations	$	9,381
	Liabilities incurred		27
	Liabilities settled		(58	)
	Accretion expense		271
	Ending asset retirement obligations	$	9,621

Derivatives_and_Financial_Inst1

Derivatives and Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative [Line Items]
Summary of Fair Value and Classification of Derivative Instruments	The table below summarizes the fair value and classification of the Company’s derivative instruments:
	As of March 31, 2015
	(In thousands)
	Classification	Balance Sheet Location		Gross Fair				Effect of				Net Carrying
				Value				Counterparty				Value on
								Netting				Balance Sheet
	Assets:
	Current asset	Commodity derivative assets		$	39,055			$	(142	)		$	38,913
	Non-current asset	Deferred charges and other long-term assets			992				(200	)			792
	Total assets			$	40,047			$	(342	)		$	39,705
	Liabilities:
	Current liability	Commodity derivative liabilities		$	142			$	(142	)		$	—
	Non-current liability	Commodity derivative liabilities			237				(200	)			37
	Total liabilities			$	379			$	(342	)		$	37
	As of December 31, 2014
	(In thousands)
	Classification	Balance Sheet Location		Gross Fair				Effect of				Net Carrying
				Value				Counterparty				Value on
								Netting				Balance Sheet
	Assets:
	Current asset	Commodity derivative assets		$	37,656			$	(185	)		$	37,471
	Non-current asset	Deferred charges and other long-term assets			—				—				—
	Total assets			$	37,656			$	(185	)		$	37,471
	Liabilities:
	Current liability	Commodity derivative liability		$	185			$	(185	)		$	—
	Non-current liability	Commodity derivative liability			—				—				—
	Total liabilities			$	185			$	(185	)		$	—
Changes in Fair Value of Company's Commodity Derivative Instruments	. Changes in the fair value of the Company’s commodity derivative instruments (both assets and liabilities) are as follows:
		For the three months ended March 31,
	Derivatives not designated as hedging instruments under ASC 815	2015				2014
		(In thousands)
	Beginning fair value of commodity derivative instruments	$	37,471			$	(1,812	)
	Gain (loss) on oil derivative instruments		13,019				(1,551	)
	Gain (loss) on natural gas derivative instruments		6,628				(4,444	)
	Net cash (received) paid on settlements of oil derivative		(11,509	)			18
	instruments
	Net cash (received) paid on settlements of natural gas		(5,941	)			2,066
	derivative instruments
	Net change in fair value of commodity derivative		2,197				(3,911	)
	instruments
	Ending fair value of commodity derivative instruments	$	39,668			$	(5,723	)
Natural Gas
Derivative [Line Items]
Summary of Open Derivative Contracts	The Company had the following open derivative contracts for natural gas as of March 31, 2015:
		Volume				Weighted Average				Range (Per MMBtu)
	Period and Type of Contract	(MMBtu)				(Per MMBtu)				Low				High
	Natural Gas Collars:
	2015
	Collar contracts:
	Call Options		3,640,000			$	4.82			$	4.51			$	5.13
	Put Options		3,640,000			$	3.81			$	3.5			$	4
	Natural Gas Swaps:
	2015
	Swap contracts:		18,580,000			$	3.12			$	2.72			$	3.53
	2016
	Swap contracts:		22,450,000			$	3.18			$	3.03			$	3.41
Oil
Derivative [Line Items]
Summary of Open Derivative Contracts	The Company had the following open derivative contracts for oil as of March 31, 2015:
		Volume				Weighted Average				Range (Per Bbl)
	Period and Type of Contract	(Bbl)				(Per Bbl)				Low				High
	Oil Collars:
	2015
	Collar contracts:
	Call Options		625,000			$	102.02			$	99.05			$	104
	Put Options		625,000			$	84.88			$	80			$	90
	Oil Swaps:
	2015
	Swap contracts:		1,106,000			$	58.71			$	52.05			$	61.71
	2016
	Swap contracts:		1,540,000			$	57.98			$	54.8			$	60.41

Fair_Value_Measurement_Tables

Fair Value Measurement (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table presents information about the Company’s assets and liabilities measured at fair value on a recurring basis:
		Fair Value Measurements Using						Effect of
								Counterparty
		Level 1		Level 2		Level 3		Netting			Total
		(In thousands)
	As of March 31, 2015
	Financial Assets
	Commodity derivative instruments	$	—	$	40,047	$	—	$	(342	)	$	39,705
	Financial Liabilities
	Commodity derivative instruments		—		379		—		(342	)	$	37
	As of December 31, 2014
	Financial Assets
	Commodity derivative instruments	$	—	$	37,656	$	—	$	(185	)	$	37,471
	Financial Liabilities
	Commodity derivative instruments		—		185		—		(185	)	$	—
Schedule of Assets Measured at Fair Value on a Non Recurring Basis	The following table presents information about the Company’s assets measured at fair value on a non-recurring basis:
		Fair Value Measurements Using						Net Book			Impairment
		Level 1		Level 2		Level 3		Value			Loss
		(In thousands)
	As of March 31, 2015
	Impaired oil and natural gas properties	$	—	$	—	$	17,826	$	31,293		$	13,467
	As of December 31, 2014
	Impaired oil and natural gas properties	$	—	$	—	$	81,864	$	199,794		$	117,930

Earnings_Per_Unit_Tables

Earnings Per Unit (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings per Unit	The following table sets forth the computation of basic and diluted earnings per unit:
		Three Months Ended March 31,
		2015			2014
		(In thousands, except per unit
		amounts)
	Net income	$	17,299		$	69,884
	Net (income) loss attributable to noncontrolling interests		(9	)		3
	Dividends on preferred units		(2,909	)		(3,882	)
	Net income attributable to the general partner and	$	14,381		$	66,005
	limited partners
	Allocation of net income attributable to:
	General partner interest	$	—		$	—
	Common limited partner interest		14,381			66,005
		$	14,381		$	66,005
	Net income attributable to limited partners per unit:
	Per common limited partner unit (basic and diluted)	$	0.09		$	0.4
	Weighted average common limited partner units outstanding (basic and diluted)		167,452			164,585

Business_and_Basis_of_Presenta1

Business and Basis of Presentation - Additional Information (Details) (USD $)	0 Months Ended
In Millions, except Share data, unless otherwise specified	6-May-15	Mar. 31, 2015
Limited Partners Capital Account [Line Items]
Cost basis, ownership percentage		20.00%
U.S.
Limited Partners Capital Account [Line Items]
Number of states major onshore oil and natural gas basins located		41
Number of onshore oil and natural gas producing basins		62
Subsequent Event | IPO | Limited Partner
Limited Partners Capital Account [Line Items]
Units issued in public offering	22,500,000
Price per common unit (in dollars per unit)	$19
Subsequent Event | Common Units | Predecessor
Limited Partners Capital Account [Line Items]
Units exchanged in merger	72,574,715
Units conversion ratio as part of merger	12.9465
Subsequent Event | Common Units | IPO | Limited Partner
Limited Partners Capital Account [Line Items]
Units issued in public offering	22,500,000
Price per common unit (in dollars per unit)	$19
Proceeds from sale of common units, net of offering expenses and underwriting discounts and commissions	$391.60
Subsequent Event | Subordinate Units | Predecessor
Limited Partners Capital Account [Line Items]
Units exchanged in merger	95,057,312
Units conversion ratio as part of merger	12.9465
Subsequent Event | Preferred Units | Predecessor
Limited Partners Capital Account [Line Items]
Units exchanged in merger	117,963
Units conversion ratio as part of merger	1

Asset_Retirement_Obligations_S

Asset Retirement Obligations - Schedule of Change in Asset Retirement Obligation Liability (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]
Beginning asset retirement obligations	$9,381
Asset retirement obligations incurred	27	31
Liabilities settled	-58
Accretion expense	271	147
Ending asset retirement obligations	$9,621

Derivatives_and_Financial_Inst2

Derivatives and Financial Instruments - Summary of Fair Value and Classification of Derivative Instruments (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Derivatives Fair Value [Line Items]
Gross Fair Value, Assets	$40,047	$37,656
Effect of Counterparty Netting, Assets	-342	-185
Net Carrying Value on Balance Sheet, Assets	39,705	37,471
Gross Fair Value, Liabilities	379	185
Effect of Counterparty Netting, Liabilities	-342	-185
Net Carrying Value on Balance Sheet, Liabilities	37
Commodity Derivative Assets, Current
Derivatives Fair Value [Line Items]
Gross Fair Value, Assets	39,055	37,656
Effect of Counterparty Netting, Assets	-142	-185
Net Carrying Value on Balance Sheet, Assets	38,913	37,471
Deferred Charges and Other Long-term Assets, Non-current
Derivatives Fair Value [Line Items]
Gross Fair Value, Assets	992
Effect of Counterparty Netting, Assets	-200
Net Carrying Value on Balance Sheet, Assets	792
Commodity Derivative Liabilities, Current
Derivatives Fair Value [Line Items]
Gross Fair Value, Liabilities	142	185
Effect of Counterparty Netting, Liabilities	-142	-185
Commodity Derivative Liabilities, Non-current
Derivatives Fair Value [Line Items]
Gross Fair Value, Liabilities	237
Effect of Counterparty Netting, Liabilities	-200
Net Carrying Value on Balance Sheet, Liabilities	$37

Derivatives_and_Financial_Inst3

Derivatives and Financial Instruments - Changes in Fair Value of Company's Commodity Derivative Instruments (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Derivative [Line Items]
Gain (loss) on commodity derivative instruments	$19,647	($5,995)
Net cash (received) paid on settlements of derivative instruments	-17,450	2,084
Not Designated as Hedging Instrument
Derivative [Line Items]
Beginning fair value of commodity derivative instruments	37,471	-1,812
Net change in fair value of commodity derivative instruments	2,197	-3,911
Ending fair value of commodity derivative instruments	39,668	-5,723
Oil | Not Designated as Hedging Instrument
Derivative [Line Items]
Gain (loss) on commodity derivative instruments	13,019	-1,551
Net cash (received) paid on settlements of derivative instruments	-11,509	18
Natural Gas | Not Designated as Hedging Instrument
Derivative [Line Items]
Gain (loss) on commodity derivative instruments	6,628	-4,444
Net cash (received) paid on settlements of derivative instruments	($5,941)	$2,066

Derivatives_and_Financial_Inst4

Derivatives and Financial Instruments - Summary of Open Derivative Contracts (Details) (Not Designated as Hedging Instrument)	3 Months Ended
	Mar. 31, 2015
	bbl
Oil | 2015 | 2015 Collar Contracts | Call Options
Derivative [Line Items]
Derivative Contract, Volume	625,000
Derivative Contract, Weighted Average Price	102.02
Derivative Contract, Price Range Low	99.05
Derivative Contract, Price Range High	104
Oil | 2015 | 2015 Collar Contracts | Put Options
Derivative [Line Items]
Derivative Contract, Volume	625,000
Derivative Contract, Weighted Average Price	84.88
Derivative Contract, Price Range Low	80
Derivative Contract, Price Range High	90
Oil | 2015 | Swap Contracts | Swap
Derivative [Line Items]
Derivative Contract, Volume	1,106,000
Derivative Contract, Weighted Average Price	58.71
Derivative Contract, Price Range Low	52.05
Derivative Contract, Price Range High	61.71
Oil | 2016 | Swap Contracts | Swap
Derivative [Line Items]
Derivative Contract, Volume	1,540,000
Derivative Contract, Weighted Average Price	57.98
Derivative Contract, Price Range Low	54.8
Derivative Contract, Price Range High	60.41
Natural Gas | 2015 | 2015 Collar Contracts | Call Options
Derivative [Line Items]
Derivative Contract, Volume	3,640,000
Derivative Contract, Weighted Average Price	4.82
Derivative Contract, Price Range Low	4.51
Derivative Contract, Price Range High	5.13
Natural Gas | 2015 | 2015 Collar Contracts | Put Options
Derivative [Line Items]
Derivative Contract, Volume	3,640,000
Derivative Contract, Weighted Average Price	3.81
Derivative Contract, Price Range Low	3.5
Derivative Contract, Price Range High	4
Natural Gas | 2015 | Swap Contracts | Swap
Derivative [Line Items]
Derivative Contract, Volume	18,580,000
Derivative Contract, Weighted Average Price	3.12
Derivative Contract, Price Range Low	2.72
Derivative Contract, Price Range High	3.53
Natural Gas | 2016 | Swap Contracts | Swap
Derivative [Line Items]
Derivative Contract, Volume	22,450,000
Derivative Contract, Weighted Average Price	3.18
Derivative Contract, Price Range Low	3.03
Derivative Contract, Price Range High	3.41

Fair_Value_Measurements_Schedu

Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gross Fair Value, Assets	$40,047	$37,656
Effect of Counterparty Netting, Assets	-342	-185
Net Carrying Value on Balance Sheet, Assets	39,705	37,471
Gross Fair Value, Liabilities	379	185
Effect of Counterparty Netting, Liabilities	-342	-185
Net Carrying Value on Balance Sheet, Liabilities	37
Commodity Derivative Instruments | Fair Value Measurements, Recurring Basis | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gross Fair Value, Assets	40,047	37,656
Effect of Counterparty Netting, Assets	-342	-185
Net Carrying Value on Balance Sheet, Assets	39,705	37,471
Gross Fair Value, Liabilities	379	185
Effect of Counterparty Netting, Liabilities	-342	-185
Net Carrying Value on Balance Sheet, Liabilities	$37

Fair_Value_Measurements_Schedu1

Fair Value Measurements - Schedule of Assets Measured at Fair Value on a Non Recurring Basis (Details) (USD $)	3 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Impaired oil and natural gas properties, Impairment Loss	$13,467
Fair Value Measurements, Nonrecurring Basis
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Impaired oil and natural gas properties, Net Book Value	31,293	199,794
Impaired oil and natural gas properties, Impairment Loss	13,467	117,930
Fair Value Measurements, Nonrecurring Basis | Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Impaired oil and natural gas properties, Fair Value Measurements	$17,826	$81,864

Related_Party_Transactions_Add

Related Party Transactions - Additional Information (Details) (Officer, USD $)	0 Months Ended
In Millions, unless otherwise specified	Apr. 15, 2010	Mar. 31, 2014
Officer
Related Party Transaction [Line Items]
Promissory note, executed amount	$0.50
Promissory notes receivable		$0.10

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Details) (USD $)	Mar. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Provision for remediation costs	$0

Credit_Facility_Additional_Inf

Credit Facility - Additional Information (Details) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2012	Jan. 23, 2015	Dec. 31, 2014	Jun. 28, 2013	Apr. 10, 2015
Line Of Credit Facility [Line Items]
Credit facilities	$389,000,000			$394,000,000
Senior Line of Credit
Line Of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity		600,000,000			1,000,000
Line of credit, borrowing base	700,000,000			700,000,000
Line of credit facility, expiration date		3-Feb-17
Line of credit, prime rate description	The prime rate is determined to be the higher of the financial institutionbs prime rate or the federal funds effective rate plus 0.50% per annum
Line of credit, weighted average interest rate	2.18%			2.41%
Line of credit, accrued interest periodic payments	Accrued interest is payable at the end of each calendar quarter or at the end of each interest period, unless the interest period is longer than 90 days in which case interest is payable at the end of every 90-day period.
Line of credit facility, frequency of commitment fee payment	Commitment fee is payable at the end of each calendar
Credit facilities	389,000,000			394,000,000
Line of credit, unused portion of current borrowing base	311,000,000			306,000,000
Senior Line of Credit | Borrowing Base Utilization Percentage Less Than 50%
Line Of Credit Facility [Line Items]
Line of credit, commitment fee payable rate	0.38%
Senior Line of Credit | Borrowing Base Utilization Percentage Equal to or Greater Than 50%
Line Of Credit Facility [Line Items]
Line of credit, commitment fee payable rate	0.50%
Senior Line of Credit | Minimum
Line Of Credit Facility [Line Items]
Line of credit, current ratio	100.00%
Senior Line of Credit | Maximum
Line Of Credit Facility [Line Items]
Line of credit, ratio of total debt to EBITDAX	350.00%
Senior Line of Credit | LIBOR Plus Margin Rate | Minimum
Line Of Credit Facility [Line Items]
Line of credit, interest rate			1.50%
Senior Line of Credit | LIBOR Plus Margin Rate | Maximum
Line Of Credit Facility [Line Items]
Line of credit, interest rate			2.50%
Senior Line of Credit | Prime Rate Plus Margin Rate | Minimum
Line Of Credit Facility [Line Items]
Line of credit, interest rate			0.50%
Senior Line of Credit | Prime Rate Plus Margin Rate | Maximum
Line Of Credit Facility [Line Items]
Line of credit, interest rate			1.50%
Senior Line of Credit | Federal funds effective rate
Line Of Credit Facility [Line Items]
Line of credit, interest rate			0.50%
Senior Line of Credit | Subsequent Event
Line Of Credit Facility [Line Items]
Line of credit, borrowing base						$600,000,000

Redeemable_Preferred_Units_Add

Redeemable Preferred Units - Additional Information (Details) (USD $)	0 Months Ended	3 Months Ended
	Jan. 02, 2015	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Class Of Stock [Line Items]
Dividends on preferred units		$2,909,000
Preferred Units
Class Of Stock [Line Items]
Partners' equity, preferred units, outstanding		117,980		157,203
Preferred units, outstanding value		120,900,000		161,200,000
Accrued and unpaid dividends		2,900,000		4,000,000
Preferred units dividend coupon rate		10.00%
Dividends on preferred units		2,900,000	3,900,000
Initial conversion price		$14.27
Initial conversion rate		70.0858
Preferred units, redemption terms		In the event the preferred unitholders have not converted all of the preferred units by December 31, 2014, the owners of the preferred units can elect to have the Company redeem up to 25% per year of its preferred units at face value, plus any accrued and unpaid dividends, on December 31 of each year from 2014 to 2017. The Company shall have the right, at its sole option, to redeem an amount of preferred units equal to the units being redeemed by an owner of preferred units on each December 31. Any amount of a given yearbs 25% of preferred units not redeemed on December 31 shall automatically convert to common units on January 1 of the following year.
Redemption percentage		25.00%
Preferred units redemption period start date		31-Dec-14
Preferred units redemption period end date		31-Dec-17
Number of preferred units converted	39,223	39,223	0
Conversion of preferred units to common units	$39,200,000	$39,200,000
Common Units
Class Of Stock [Line Items]
Converted into common units	2,748,974	2,748,974

Earnings_Per_Unit_Additional_I

Earnings Per Unit - Additional Information (Details) (Common Units)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Common Units
Earnings Per Share Basic [Line Items]
Common units issuable upon conversion of preferred units excluded from the calculation of diluted EPU	8.3	11

Earnings_Per_Unit_Computation_

Earnings Per Unit - Computation of Basic and Diluted Earnings per Unit (Details) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share Basic [Line Items]
Net income	$17,299	$69,884
NET (INCOME) LOSS ATTRIBUTABLE TO NONCONTROLLING INTERESTS	-9	3
DIVIDENDS ON PREFERRED UNITS	-2,909	-3,882
NET INCOME ATTRIBUTABLE TO THE GENERAL PARTNER AND LIMITED PARTNERS	14,381	66,005
Allocation of net income attributable to:
Common limited partner interest	14,381	66,005
NET INCOME ATTRIBUTABLE TO THE GENERAL PARTNER AND LIMITED PARTNERS	$14,381	$66,005
Common Units
Net income attributable to limited partners per unit:
Per common limited partner unit (basic)	$0.09	$0.40
Per common limited partner unit (diluted)	$0.09	$0.40
Weighted average common limited partner units outstanding (basic and diluted)	167,452	164,585

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Details) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	6-May-15	Apr. 14, 2015	Dec. 31, 2014	Apr. 10, 2015
Subsequent Event [Line Items]
Distributions made to common unit holders	$56,483,000	$55,517,000
Distributions made to preferred unit holders	2,909,000
Preferred Units
Subsequent Event [Line Items]
Distributions made to preferred unit holders	2,900,000	3,900,000
Senior Line of Credit
Subsequent Event [Line Items]
Borrowing base for senior line of credit re determined	700,000,000				700,000,000
Subsequent Event | IPO | Limited Partner
Subsequent Event [Line Items]
Units issued in public offering			22,500,000
Price per common unit (in dollars per unit)			$19
Subsequent Event | Common Units
Subsequent Event [Line Items]
Distributions made to common unit holders				56,300,000
Subsequent Event | Common Units | IPO | Limited Partner
Subsequent Event [Line Items]
Units issued in public offering			22,500,000
Price per common unit (in dollars per unit)			$19
Subsequent Event | Preferred Units
Subsequent Event [Line Items]
Distributions made to preferred unit holders				2,900,000
Subsequent Event | Senior Line of Credit
Subsequent Event [Line Items]
Borrowing base for senior line of credit re determined						$600,000,000