Pioneer Southwest Energy Partners 10-Q 6 Nov 13 2013 Q3 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	9 Months Ended
	Sep. 30, 2013	Nov. 04, 2013
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Entity Registrant Name	'Pioneer Southwest Energy Partners L.P.	'
Entity Central Index Key	'0001407463	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Accelerated Filer	'
Entity Common Units Outstanding	'	35,713,700

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'	'
Cash	$4,813	$1,601
Accounts Receivable:	'	'
Trade	22,188	15,651
Due from affiliates	391	0
Inventories	1,307	1,388
Prepaid expenses	148	228
Deferred tax assets, current	96	89
Derivative assets, current	5,238	4,553
Total current assets	34,181	23,510
Oil and gas properties, using the successful efforts method of accounting:	'	'
Proved properties	664,765	556,915
Unproved properties	6,727	5,682
Accumulated depletion, depreciation and amortization	-187,253	-163,542
Total property, plant and equipment	484,239	399,055
Derivative assets, noncurrent	3,055	7,227
Other assets, net	904	1,097
Total assets	522,379	430,889
Accounts payable:	'	'
Trade	33,982	15,557
Due to affiliates	0	1,277
Interest payable	11	9
Income taxes payable to affiliate	162	70
Derivative liabilities, current	4,795	13,390
Asset retirement obligations	600	900
Other current liabilities	109	146
Total current liabilities	39,659	31,349
Long-term debt	201,000	126,000
Derivative liabilities, noncurrent	0	150
Deferred tax liabilities, noncurrent	879	156
Asset retirement obligations	11,087	11,201
Other noncurrent liabilities	355	400
Partners' equity:	'	'
General partner's interest - 35,750 general partner units issued and outstanding	423	416
Limited partners' interest - 35,713,700 common units issued and outstanding	268,976	261,217
Total partners' equity	269,399	261,633
Commitments and contingencies	'	'
Total liabilities and partners' equity	$522,379	$430,889

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical)	Sep. 30, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]	'	'
General partner's interest, units issued	35,750	35,750
General partner's interest, units outstanding	35,750	35,750
Limited partners' interest, units issued	35,713,700	35,713,700
Limited partners' interest, units outstanding	35,713,700	35,713,700

Consolidated_Statements_Of_Ope

Consolidated Statements Of Operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues:	'	'	'	'
Oil and gas	$63,013	$46,385	$163,832	$139,655
Derivative gains (losses), net	-11,380	-13,592	-7,230	18,176
Revenues	51,633	32,793	156,602	157,831
Costs and expenses:	'	'	'	'
Oil and gas production	16,704	14,468	44,718	36,487
Production and ad valorem taxes	4,793	3,974	13,273	11,801
Depletion, depreciation and amortization	8,886	5,771	23,711	15,589
General and administrative	1,950	1,888	5,691	5,548
Accretion of discount on asset retirement obligations	209	189	623	567
Interest	1,027	638	2,848	1,456
Other	2,058	221	2,058	969
Total cost and expenses	35,627	27,149	92,922	72,417
Income before income taxes	16,006	5,644	63,680	85,414
Income tax provision	-249	-111	-835	-1,062
Net income	15,757	5,533	62,845	84,352
Allocation of net income:	'	'	'	'
General partner's interest	16	6	63	84
Limited partners' interest	15,689	5,474	62,631	84,058
Unvested participating securities' interest	52	53	151	210
Net income	$15,757	$5,533	$62,845	$84,352
Net income per common unit - basic and diluted	$0.44	$0.15	$1.75	$2.35
Weighted average common units outstanding - basic and diluted	35,714	35,714	35,714	35,714
Distributions declared per common unit	$0.52	$0.52	$1.56	$1.55

Consolidated_Statement_Of_Part

Consolidated Statement Of Partners' Equity (USD $)	Total	General Partner [Member]	Limited Partner [Member]
In Thousands, unless otherwise specified
Balance at Dec. 31, 2012	$261,633	$416	$261,217
Balance, units at Dec. 31, 2012	'	36	35,714
Increase (Decrease) in Partners' Capital [Roll Forward]	'	'	'
Cash distributions to partners	-55,769	-56	-55,713
Net income	62,845	63	62,782
Contributions of unit-based compensation	690	'	690
Balance at Sep. 30, 2013	$269,399	$423	$268,976
Balance, units at Sep. 30, 2013	'	36	35,714

Consolidated_Statement_Of_Part1

Consolidated Statement Of Partners' Equity (Parentheticals) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Partners' Capital [Abstract]	'	'	'	'
Distributions declared per common unit	$0.52	$0.52	$1.56	$1.55

Consolidated_Statements_Of_Cas

Consolidated Statements Of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:	'	'
Net income	$62,845	$84,352
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depletion, depreciation and amortization	23,711	15,589
Deferred income taxes	716	957
Accretion of discount on asset retirement obligations	623	567
Amortization of debt related costs	194	174
Amortization of unit-based compensation	690	639
Commodity derivative related activity	-5,258	-28,700
Other noncash expense	0	969
Change in operating assets and liabilities:	'	'
Accounts receivable	-6,928	1,531
Inventories	81	-353
Prepaid expenses	80	-91
Accounts payable	6,735	6,241
Interest payable	2	127
Income taxes payable to affiliate	92	-430
Asset retirement obligations	-1,325	-1,477
Other current liabilities	-82	-296
Net cash provided by operating activities	82,176	79,799
Cash flows from investing activities:	'	'
Additions to oil and gas properties	-98,195	-76,778
Net cash used in investing activities	-98,195	-76,778
Cash flows from financing activities:	'	'
Borrowings under credit facility	75,000	107,000
Principal payments on credit facility	0	-51,000
Payment of financing fees	0	-1,291
Distributions to unitholders	-55,769	-55,412
Net cash provided by (used in) financing activities	19,231	-703
Net increase in cash	3,212	2,318
Cash, beginning of period	1,601	1,176
Cash, end of period	$4,813	$3,494

Partnership_And_Nature_Of_Oper

Partnership And Nature Of Operations	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Partnership And Nature Of Operations	'
	Partnership and Nature of Operations
	Pioneer Southwest Energy Partners L.P. (the "Partnership") is a Delaware limited partnership that was formed in June 2007 by Pioneer Natural Resources Company (together with its subsidiaries, "Pioneer") to own, acquire, explore and develop oil and gas assets in the Partnership's area of operations. The Partnership's area of operations consists of onshore Texas and eight counties in the southeast region of New Mexico.
	As of September 30, 2013, Pioneer owns a 52.4 percent limited partner interest in the Partnership and Pioneer owns and controls Pioneer Natural Resources GP LLC (the "General Partner"), which manages the Partnership.

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	Presentation. In the opinion of management, the consolidated financial statements of the Partnership as of September 30, 2013, and for the three and nine months ended September 30, 2013 and 2012, include all adjustments and accruals, consisting only of normal recurring accrual adjustments, which are necessary for a fair presentation of the results for the interim periods. These interim results are not necessarily indicative of results for a full year.
	Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States ("GAAP") have been condensed in or omitted from this report pursuant to the rules and regulations of the United States Securities and Exchange Commission (the "SEC"). These consolidated financial statements should be read together with the consolidated financial statements and notes thereto included in the Partnership's Annual Report on Form 10-K for the year ended December 31, 2012.
	Merger Agreement with Pioneer. On August 9, 2013, the Partnership entered into an Agreement and Plan of Merger with Pioneer, Pioneer Natural Resources USA, Inc., a wholly-owned subsidiary of Pioneer ("Pioneer USA"), PNR Acquisition Company, LLC, a wholly-owned subsidiary of Pioneer ("MergerCo"), and the General Partner, which was amended on October 25, 2013 (as amended, the "Merger Agreement").
	Pursuant to the Merger Agreement, MergerCo will merge with and into the Partnership, with the Partnership surviving the merger (the "Merger"), such that following the Merger, the General Partner will remain a wholly-owned subsidiary of Pioneer and the sole general partner of the Partnership, and Pioneer USA will be the sole limited partner of the Partnership. Except for the common units owned by Pioneer, all of the common units outstanding as of the closing of the Merger will be cancelled and, except for the dissenting units (as defined in the next paragraph), converted into the right to receive 0.2325 of a share of common stock of Pioneer per common unit.
	Pursuant to the terms and conditions of the Merger Agreement, common units that are owned by a unitholder (a) other than the Partnership or its subsidiaries or Pioneer or its subsidiaries, (b) who does not vote at the special meeting of the Partnership in favor of the proposal to approve the Merger Agreement and the transactions contemplated thereby, including the Merger, and (c) who is entitled to demand and properly demands appraisal of such common units (the "dissenting units") pursuant to, and who complies in all respects with, the provisions of the Merger Agreement regarding appraisal rights (the "dissenting unitholders") will not be converted into the right to receive the merger consideration, but instead will be entitled to payment of the fair value of such dissenting units pursuant to and in accordance with the provisions of the Merger Agreement, unless and until such dissenting unitholder shall have failed to perfect or shall have effectively withdrawn or lost the appraisal rights. If a dissenting unitholder fails to perfect or effectively withdraws or loses the appraisal rights, then, as of the occurrence of such event or the closing of the Merger, whichever occurs later, each of such dissenting unitholder's dissenting units will be converted into the right to receive 0.2325 of a share of common stock of Pioneer per common unit.
	The Merger Agreement provides that regular quarterly distributions on the Partnership's common units, not to exceed $0.52 per common unit per quarter (which $0.52 per common unit is equivalent to the most recent distribution declared for the quarter ended September 30, 2013), are to continue until the closing of the Merger. Regular distributions for a quarter are declared late in the first month following such quarter, and no distribution will be paid for a quarter if the Merger closes prior to the normal record date for such distribution. No fractional shares of Pioneer common stock will be issued in the Merger. In lieu of receiving any fractional share of Pioneer common stock to which any holder of the Partnership's common units would otherwise have been entitled, after aggregating all fractions of shares to which such holder would be entitled, any fractional share will be rounded up to a whole share of Pioneer common stock. The closing of the Merger is subject to certain closing conditions, including the approval of the Merger Agreement and the transactions contemplated thereby by the affirmative vote of holders of a majority of the outstanding common units entitled to vote at a special meeting of the unitholders of the Partnership. Pursuant to a voting agreement, Pioneer has agreed to cause the common units owned by it and its subsidiaries to be voted in favor of the Merger, which units represent 52.4 percent of the Partnership's outstanding common units and therefore constitute a sufficient number of common units to approve the Merger at the special meeting of the unitholders of the Partnership. The parties anticipate that the Merger will close in the fourth quarter of 2013, pending satisfaction of certain conditions thereto. See Note J for a description of the litigation contingencies associated with the Merger.
	Net income per common unit. Net income per common unit is calculated by dividing the limited partners' interest in net income (which excludes net income allocable to unvested participating securities) by the weighted average number of common units outstanding.
	The Partnership applies the provisions of Accounting Standards Codification ("ASC") Topic 260 "Earnings Per Share" when determining net income per common unit. Instruments granted in unit-based payment transactions that are determined to be participating securities prior to vesting are included in the net income allocation in computing basic and diluted net income per unit. Participating securities represent unvested unit-based compensation awards that have non-forfeitable distribution rights during their vesting periods, such as the phantom units and restricted units awarded under the Pioneer Southwest Energy Partners L.P. 2008 Long Term Incentive Plan (the "LTIP").
	The Partnership's net income is allocated to partners' equity accounts in accordance with the provisions of the First Amended and Restated Agreement of Limited Partnership of Pioneer Southwest Energy Partners L.P. (the "Partnership Agreement").

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	Fair Value Measurements
	Fair value is defined as the price that would be received to sell an asset or the price that would be paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value measurements are based upon inputs that market participants use in pricing an asset or liability, which are characterized according to a hierarchy that prioritizes those inputs based on the degree to which they are observable. Observable inputs represent market data obtained from independent sources, whereas unobservable inputs reflect a company's own market assumptions, which are used if observable inputs are not reasonably available without undue cost and effort. The three input levels of the fair value hierarchy are as follows:
	•Level 1 – quoted prices for identical assets or liabilities in active markets.
	•	Level 2 – quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar assets or liabilities in markets that are not active; inputs other than quoted prices that are observable for the asset or liability (e.g. interest rates) and inputs derived principally from or corroborated by observable market data by correlation or other means.
	•	Level 3 – unobservable inputs for the asset or liability.
	Assets and liabilities measured at fair value on a recurring basis. The fair value input hierarchy level to which an asset or liability measurement in its entirety falls is determined based on the lowest level input that is significant to the measurement in its entirety.
	The following table presents the Partnership's assets and liabilities that are measured at fair value as of September 30, 2013:
			Fair Value Measurements at the End of the Reporting Period Using
			Quoted Prices in		Significant		Significant		Fair Value at September 30, 2013
			Active  Markets		Other		Unobservable
			for Identical		Observable		Inputs
			Assets		Inputs		(Level 3)
			(Level 1)		(Level 2)
			(in thousands)
	Recurring fair value measurements
	Assets:
	Commodity derivatives		$	—	$	8,293	$	—	$	8,293
	Liabilities:
	Commodity derivatives		—		4,795		—		4,795
	Total recurring fair value measurements		$	—	$	3,498	$	—	$	3,498
	Commodity derivatives. The Partnership's commodity derivatives represent oil and gas swap contracts, collar contracts and collar contracts with short puts. The asset and liability measurements for the Partnership's oil and gas derivative contracts represent Level 2 inputs in the hierarchy priority. The Partnership utilizes discounted cash flow and option-pricing models for valuing its commodity derivatives.
	The asset and liability values attributable to the Partnership's commodity derivatives were determined based on inputs that include (i) the contracted notional volumes, (ii) independent active market price quotes, (iii) the applicable estimated credit-adjusted risk-free rate yield curves and (iv) the implied rate of volatility inherent in the options underlying the Partnership's collar contracts and collar contracts with short puts, which is based on active and independent market-quoted volatility factors.
	Financial instruments not carried at fair value. The carrying values and fair values of financial instruments that are not recorded at fair value in the accompanying consolidated balance sheets as of September 30, 2013 and December 31, 2012 are as follows:
			September 30, 2013				December 31, 2012
			Carrying		Fair		Carrying		Fair
			Value		Value		Value		Value
			(in thousands)
	Credit facility		$	201,000	$	193,355	$	126,000	$	123,635
	Credit facility. The fair value of debt is characterized as a Level 2 measurement in the fair value hierarchy and is calculated using a discounted cash flow model based on (i) forecasted contractual interest and fee payments, (ii) forward active market-quoted London Interbank Offered Rate ("LIBOR") yield curves and (iii) the applicable credit-adjusted risk-free rate yield curve.
	The Partnership has other financial instruments consisting primarily of cash, receivables, prepaids, payables and other current assets and liabilities whose carrying values approximate their fair values due to the nature of the instruments and their relatively short maturities.

Derivative_Financial_Instrumen

Derivative Financial Instruments	9 Months Ended
	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Financial Instruments	'
	Derivative Financial Instruments
	The Partnership generally utilizes commodity swap contracts, collar contracts and collar contracts with short puts to (i) reduce the effect of price volatility on the commodities the Partnership produces and sells, (ii) support the Partnership's annual capital budgeting and expenditure plans and (iii) help sustain unitholder distributions.
	Oil production derivative activities. All material physical sales contracts governing the Partnership's oil production are tied directly or indirectly to the New York Mercantile Exchange ("NYMEX") prices. The following table sets forth the volumes per day in barrels ("BBLs") outstanding as of September 30, 2013 under the Partnership's oil derivative contracts and the weighted average NYMEX prices per BBL for those contracts as of September 30, 2013:
		Three Months Ending			Year Ending
		December 31,			December 31,
		2013			2014
	Collar contracts with short puts:
	Volume (BBLs per day)	—			5,000
	Average price per BBL:
	Ceiling	$	—		$	105.74
	Floor	$	—		$	100
	Short put	$	—		$	80
	Swap contracts:
	Volume (BBLs per day)	4,750			—
	Average price per BBL	$	87.83		$	—
	Gas production derivative activities. All material physical sales contracts governing the Partnership's gas production are tied directly or indirectly to regional index prices where the gas is sold. The Partnership uses derivative contracts to manage gas price volatility and basis swap contracts to reduce basis risk between the Permian Basin index price and the NYMEX Henry Hub index price used in gas swap contracts. The following table sets forth the volumes in millions of British Thermal Units ("MMBTUs") under outstanding gas derivative contracts and the weighted average index prices per MMBTU for those contracts as of September 30, 2013:
		Three Months Ending December 31,			Year Ending
					December 31,
		2013			2014			2015
	Collar contracts with short puts:
	Volume (MMBTUs per day)	—			—			5,000
	Average price per MMBTU:
	Ceiling	$	—		$	—		$	5
	Floor	$	—		$	—		$	4
	Short put	$	—		$	—		$	3
	Collar contracts:
	Volume (MMBTUs per day)	2,500			—			—
	Average price per MMBTU:
	Ceiling	$	4.5		$	—		$	—
	Floor	$	4		$	—		$	—
	Swap contracts:
	Volume (MMBTUs per day)	2,500			5,000			—
	Average price per MMBTU	$	6.89		$	4		$	—
	Basis swap contracts:
	Permian Basin index swaps - (MMBTUs per day)	2,500			—			—
	Price differential ($/MMBTU)	$	(0.31	)	$	—		$	—
	Tabular disclosure of derivative financial instruments. All of the Partnership's derivatives are accounted for as non-hedge derivatives as of September 30, 2013 and December 31, 2012 and therefore all changes in the fair values of its derivative contracts are recognized as gains or losses in the earnings of the periods in which they occur. The Partnership recognized derivative losses on commodity contracts of $11.4 million and $7.2 million during the three and nine months ended September 30, 2013, respectively, as compared to derivative losses of $13.6 million and derivative gains of $18.2 million for the three and nine months ended September 30, 2012, respectively, which are reflected in net derivative gains (losses) in the accompanying consolidated statement of operations. The Partnership classifies the fair value amounts of derivative assets and liabilities as net current or noncurrent derivative assets or net current or noncurrent derivative liabilities, whichever the case may be, by commodity and counterparty. The Partnership enters into derivatives under master netting agreements, which, in an event of default, allows the Partnership to offset payables to and receivables from the defaulting counterparty.
	The aggregate fair value of the Partnership's derivative instruments that are reported in the consolidated balance sheets consists of the following:
	Fair Value of Derivative Instruments as of September 30, 2013
	Consolidated Balance Sheet Location	Fair			Gross Amounts Offset in the Consolidated Balance Sheet			Net Fair Value Presented in the Consolidated Balance Sheet
		Value
		(in thousands)
	Derivatives not designated as hedging instruments
	Asset Derivatives:
	Derivatives - current	$	6,465		$	(1,227	)	$	5,238
	Derivatives - noncurrent	$	3,071		$	(16	)	3,055
								$	8,293
	Liability Derivatives:
	Derivatives - current	$	6,022		$	(1,227	)	$	4,795
	Derivatives - noncurrent	$	16		$	(16	)	—
								$	4,795
	Fair Value of Derivative Instruments as of December 31, 2012
	Consolidated Balance Sheet Location	Fair			Gross Amounts Offset in the Consolidated Balance Sheet			Net Fair Value Presented in the Consolidated Balance Sheet
		Value
		(in thousands)
	Derivatives not designated as hedging instruments
	Asset Derivatives:
	Derivatives - current	$	4,553		$	—		$	4,553
	Derivatives - noncurrent	$	7,278		$	(51	)	7,227
								$	11,780
	Liability Derivatives:
	Derivatives - current	$	13,390		$	—		$	13,390
	Derivatives - noncurrent	$	201		$	(51	)	150
							$	13,540
The Partnership uses credit and other financial criteria to evaluate the credit standing of, and to select, counterparties to its derivative instruments. Although the Partnership does not obtain collateral or otherwise secure the fair value of its derivative instruments, associated credit risk is mitigated by the Partnership's credit risk policies and procedures.

Exploratory_Costs

Exploratory Costs	9 Months Ended
	Sep. 30, 2013
Exploratory Cost Disclosure [Abstract]	'
Exploratory Costs	'
	Exploratory Costs
	The Partnership capitalizes exploratory well costs until a determination is made that the well has either found proved reserves, is impaired or is sold. The Partnership's capitalized exploratory well costs are presented in proved properties in the accompanying consolidated balance sheets. If the exploratory well is determined to be impaired, the impaired costs are charged to exploration and abandonments expense.
	The following table reflects the Partnership's capitalized exploratory well activity during the three and nine months ended September 30, 2013:
		Three Months Ended			Nine Months Ended
		September 30, 2013			September 30, 2013
		(in thousands)
	Beginning capitalized exploratory costs	$	10,572		$	—
	Additions to exploratory costs pending the determination of proved reserves	5,552			35,225
	Reclassification due to determination of proved reserves	(16,109		)	(35,210		)
	Ending capitalized exploratory costs (a)	$	15		$	15
	__________
	(a)	All capitalized exploratory costs are aged less than one year based on the date drilling was completed.

LongTerm_Debt

Long-Term Debt	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]	'
Long-Term Debt	'
	Long-term Debt
	The Partnership maintains a Credit Agreement (the "Credit Facility") with a syndicate of financial institutions that has aggregate loan commitments of $300 million that expires in March 2017. As of September 30, 2013, the Partnership had $201.0 million of borrowings outstanding under the Credit Facility. The Partnership's borrowing capacity under the Credit Facility is subject to a covenant requiring that the Partnership maintain a specified ratio of the net present value of the Partnership's projected future cash flows from its oil and gas assets to total debt, with the variables on which the calculation of net present value is based (including assumed commodity prices and discount rates) being subject to adjustment by the lenders. As a result, declines in commodity prices could reduce the Partnership's borrowing capacity under the Credit Facility and could require the Partnership to reduce its distributions to unitholders. Based on the financial covenant detailed above, the Partnership's available borrowing capacity under the Credit Facility was $68.6 million at September 30, 2013.
	During March 2013, the Partnership amended the Credit Facility to clarify the timing of the requirement to maintain swap contracts on at least 50 percent of forecasted production (the "minimum hedging requirement").  Prior to the amendment, the minimum hedging requirement was for all periods through December 31, 2014 and thereafter on a rolling basis of not less than two years or to March 2017 (the "Maturity Date").  The amended minimum hedging requirement includes all periods through December 31, 2014 and thereafter on a rolling basis of not less than four quarters, but in no case past the Maturity Date.  The Partnership accounted for the amendment as a modification of the existing Credit Facility.

Incentive_Plans

Incentive Plans	9 Months Ended
	Sep. 30, 2013
Incentive Plans [Abstract]	'
Incentive Plans	'
	Incentive Plans
	For the three and nine months ended September 30, 2013, the Partnership recognized $240 thousand and $791 thousand, respectively, of unit-based compensation, as compared to $287 thousand and $811 thousand, respectively, for the three and nine months ended September 30, 2012. As of September 30, 2013, there was $1.3 million of unrecognized compensation expense related to unvested unit-based compensation awards. This compensation will be recognized over the remaining vesting periods of the awards, which on a weighted average basis is a period of less than three years.
	The following table reflects the Partnership's outstanding unit-based awards as of September 30, 2013 and the activity related thereto for the nine months ended September 30, 2013:
		Restricted		Phantom
		Units		Units
	Outstanding at beginning of year	7,496		102,644
	Units granted	—		32,242
	Lapse of restrictions	(7,496	)	(35,118	)
	Outstanding at September 30, 2013	—		99,768

Asset_Retirement_Obligations

Asset Retirement Obligations	9 Months Ended
	Sep. 30, 2013
Asset Retirement Obligation Disclosure [Abstract]	'
Asset Retirement Obligations	'
	Asset Retirement Obligations
	The Partnership's asset retirement obligations primarily relate to the future plugging and abandonment of wells and facilities. The following table summarizes the Partnership's asset retirement obligation activity during the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2013			2012			2013			2012
		(in thousands)
	Beginning asset retirement obligations	$	11,946		$	9,867		$	12,101		$	10,315
	Liabilities settled	(636		)	(576		)	(1,325		)	(1,477		)
	New wells placed on production	168			48			288			123
	Accretion of discount	209			189			623			567
	Ending asset retirement obligations	$	11,687		$	9,528		$	11,687		$	9,528

Related_Party_Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2013
Related Party Transactions [Abstract]	'
Related Party Transactions	'
	Related Party Transactions
	In accordance with standard industry operating agreements and the various agreements entered into between the Partnership and Pioneer, the Partnership incurred the following charges from Pioneer during the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
		2013		2012		2013		2012
		(in thousands)
	Producing well overhead (COPAS) fees	$	3,074	$	2,863	$	9,083	$	8,361
	Payment of lease operating and supervision charges	3,558		2,498		9,548		7,384
	Drilling and completion related charges	11,334		8,546		38,668		28,775
	General and administrative expenses	1,298		1,181		3,648		3,422
	Total	$	19,264	$	15,088	$	60,947	$	47,942
	As of September 30, 2013, the Partnership has a net accounts receivable – due from affiliates in the accompanying consolidated balance sheet of $391 thousand, representing a $1.7 million receivable for reimbursable drilling and completion, and lease operating and supervision related charges that were provided by Pioneer, partially offset by a $1.3 million payable to Pioneer for general and administrative expenses and a $40 thousand payable to Pioneer for other miscellaneous items. As of December 31, 2012, the Partnership's net accounts payable – due to affiliates balance in the accompanying consolidated balance sheet of $1.3 million includes a $1.4 million payable to Pioneer for general and administrative expenses and a $106 thousand payable to Pioneer for other miscellaneous items, partially offset by a $266 thousand receivable for reimbursable drilling and completion related charges that were provided by Pioneer.
	As of September 30, 2013 and December 31, 2012, the Partnership had $162 thousand and $70 thousand, respectively, of income taxes payable to affiliate recorded in the accompanying consolidated balance sheets, representing amounts due to Pioneer under a tax sharing agreement between Pioneer and the Partnership.
	During the third quarter of 2013, Pioneer entered into leases on 1,200 acres in Midland County in West Texas to explore, develop and produce oil and gas from the properties and assigned to the Partnership an undivided 94 percent of Pioneer's interest in the leases in consideration for a payment to Pioneer of $2.5 million, representing a pro rata share of Pioneer's acquisition cost. There were no producing wells associated with the acquisition and the Partnership recorded the entire acquisition cost to unproved property.
	Prior to 2013, the General Partner annually awarded restricted common units to directors under the LTIP. Restricted common units were not awarded to directors under the LTIP during 2013. The Partnership paid the General Partner nil and $74 thousand during the three and nine months ended September 30, 2013, respectively, and $50 thousand and $147 thousand during the three and nine months ended September 30, 2012, respectively, which amounts represent the vested portion of the fair values of the annual director awards. In addition, the General Partner awarded 32,242 and 37,487 phantom units during the nine months ended September 30, 2013 and 2012, respectively, to certain officers of Pioneer and the General Partner, who were most responsible for the performance of the Partnership. The phantom units represent the right to receive common units after the lapse of a three-year vesting period, subject to the recipient's continuous employment with Pioneer. Distributions on the phantom units are paid concurrently with distributions paid to holders of common units. Associated therewith, the Partnership recognized general and administrative expense during the three and nine months ended September 30, 2013 of $240 thousand and $717 thousand, respectively, of which $231 thousand and $690 thousand, respectively, was noncash, as compared to $237 thousand and $664 thousand, respectively, of which $228 thousand and $639 thousand, respectively, was noncash, for the three and nine months ended September 30, 2012. The Merger Agreement provides that the phantom units outstanding as of the closing of the Merger will remain issued under the LTIP and will be converted into equivalent restricted stock units of common stock of Pioneer, with the number of shares subject to such restricted stock units adjusted to reflect the Merger exchange ratio, rounded down to the nearest whole share, but otherwise on the same terms and conditions as were applicable prior to the Merger.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies [Abstract]	'
Commitments and Contingencies Disclosure	'
	Commitments and Contingencies
	The Partnership is not currently a party to, or aware of, any material legal or governmental proceedings against it, aside from the legal proceedings described below. While many of these proceedings and claims involve inherent uncertainty, the Partnership believes that the amount of the liability, if any, ultimately incurred with respect to such proceedings and claims will not have a material adverse effect on the Partnership's consolidated financial position as a whole or on its liquidity, capital resources or future annual results of operations. The Partnership records reserves for contingencies when information available indicates that a loss is probable and the amount of the loss can be reasonably estimated.
	Lawsuits filed in state and federal courts in Texas relating to the Merger. On May 15, 2013, David Flecker, a purported unitholder of the Partnership, filed a class action petition on behalf of the Partnership's unitholders and a derivative suit on behalf of the Partnership against, Pioneer, Pioneer USA, the General Partner and the directors of the General Partner, in the 134th Judicial District of Dallas County, Texas (the "Flecker Lawsuit"). A similar class action petition and derivative suit was filed against the same defendants on May 20, 2013, in the 160th Judicial District of Dallas County, Texas, by purported unitholder Vipul Patel (the "Patel Lawsuit"). On August 27, 2013, the plaintiff in the Flecker Lawsuit filed an amended petition. On September 3, 2013, the court consolidated the Patel Lawsuit into the Flecker Lawsuit (as consolidated, the "Texas State Court Lawsuit"), and the plaintiffs filed a consolidated derivative and class action petition on September 5, 2013.
	The Texas State Court Lawsuit alleges, among other things, that the consideration offered by Pioneer in the Merger is unfair and inadequate and that, by pursuing a transaction that is the result of an allegedly conflicted and unfair process, the defendants have breached their duties under the Partnership Agreement as well as the implied covenant of good faith and fair dealing, and are engaging in self-dealing. Specifically, the lawsuit alleges that the director defendants: (i) engaged in self-dealing, failed to act in good faith toward the Partnership, and breached their duties owed to the Partnership; (ii) failed to properly value the Partnership and its various assets and operations and ignored or failed to protect against the numerous conflicts of interest arising out of the proposed transaction; and (iii) breached the implied covenant of good faith and fair dealing by engaging in a flawed merger process. The Texas State Court Lawsuit also alleges that Pioneer, Pioneer USA and the General Partner aided and abetted the director defendants in their purported breach of fiduciary duties.
	Based on these allegations, the plaintiffs in the Texas State Court Lawsuit seek to enjoin the defendants from proceeding with or consummating the proposed transaction. To the extent that the Merger is implemented before relief is granted, the plaintiffs seek to have the Merger rescinded. The plaintiffs also seek money damages and attorneys' fees. The defendants have filed a motion to dismiss the Texas State Court Lawsuit based on improper forum.
	On August 21, 2013, Allan H. Beverly, a purported unitholder, filed a class action complaint against the Partnership, Pioneer, Pioneer USA, MergerCo and the directors of the General Partner in the United States District Court for the Northern District of Texas (the "Beverly Lawsuit"). The Beverly Lawsuit alleges that the defendants breached their fiduciary duties by agreeing to the Merger by means of an unfair process and for an unfair price. Specifically, the lawsuit alleges that the director defendants: (i) failed to maximize the value of the Partnership to its public unitholders and took steps to avoid competitive bidding; (ii) failed to properly value the Partnership; and (iii) ignored or failed to protect against the numerous conflicts of interest arising out of the proposed transaction. The Beverly Lawsuit also alleges that Pioneer, Pioneer USA and MergerCo aided and abetted the director defendants in their purported breach of fiduciary duties.
	On September 13, 2013, Douglas Shelton, another purported unitholder, filed a class action complaint against the same defendants in the Beverly Lawsuit (as well as the General Partner) in the same court as the Beverly Lawsuit (the "Shelton Lawsuit"). The Shelton Lawsuit makes similar allegations to the Beverly Lawsuit, and also alleges that Section 7.9 of the Partnership Agreement fails to alter or eliminate the defendants' common law fiduciary duties owed to unitholders in the context of the Merger. Specifically, the lawsuit alleges: (i) that Pioneer, as controlling unitholder, failed to fulfill its fiduciary duties in connection with the Merger because it purportedly cannot establish that the proposed Merger is the result of a fair process that will return a fair price to the unaffiliated unitholders of the Partnership; (ii) that the director defendants breached their fiduciary duties by failing to exercise due care and diligence in connection with the proposed Merger because the proposed Merger is purportedly not the result of a fair process that will return a fair price to the unaffiliated unitholders; and (iii) that the non-director defendants aided and abetted the director defendants in their purported breach of fiduciary duties. The plaintiffs in the Beverly Lawsuit and the Shelton Lawsuit (together, the "Federal Lawsuits") seek the same remedies as the plaintiffs in the Texas State Court Lawsuit.
	On September 26, 2013, representatives of the plaintiffs in the Texas State Court Lawsuit and the Federal Lawsuits and representatives of the defendants in such lawsuits entered into a memorandum of understanding (the "memorandum of understanding") to settle the claims and allegations made in such lawsuits. The memorandum of understanding provides the plaintiffs with a period of confirmatory discovery during which the plaintiffs can confirm the fairness and reasonableness of the settlement contemplated by the memorandum of understanding. The parties agreed to use their reasonable best efforts to agree upon, execute and present to the Dallas County, Texas District Court a stipulation of settlement, which will provide for, among other things, a certification, for settlement purposes only, of the applicable class of unitholders to which the settlement will apply. Furthermore, the stipulation of settlement will provide for a full and complete discharge, dismissal with prejudice, settlement and release of all claims, suits and causes of action by the plaintiffs (other than appraisal rights under the Merger Agreement) against the defendants and their representatives arising out of or relating to the allegations made in the Texas State Court Lawsuit and the Federal Lawsuits, the Merger or any deliberations, negotiations, disclosures, omissions, press releases, statements or misstatements in connection therewith, any fiduciary or other obligations in respect of the Merger or any alternative transaction or under the Partnership Agreement, or any costs and expenses associated with settlement other than as provided in the stipulation. All proceedings relating to the allegations made in the Texas State Court Lawsuit other than with respect to the settlement have been stayed. As part of the consideration for the settlement, the Merger Agreement was amended to provide for contractual appraisal rights for the unitholders of the Partnership. The parties to the memorandum of understanding have agreed to use their reasonable best efforts to obtain the agreement of any plaintiffs filing similar lawsuits to the Texas State Court Lawsuit or the Federal Lawsuits (whether filed in any state or federal court) to become party to the memorandum of understanding and the related settlement, and it is a condition to the consummation of the final settlement that any such plaintiffs join the settlement or such similar lawsuits otherwise be dismissed with prejudice prior to the final approval of the settlement. On October 15, 2013, the plaintiffs in the Beverly Lawsuit voluntarily dismissed all claims in the lawsuit in accordance with the memorandum of understanding. On October 16, 2013, the plaintiffs in the Shelton Lawsuit likewise voluntarily dismissed all claims in the lawsuit in accordance with the memorandum of understanding. There can be no assurance that a final settlement will be consummated.
	Lawsuit filed in the Delaware Court of Chancery relating to the Merger. On September 23, 2013, Patrick Wilson, another purported unitholder, filed a class action petition on behalf of the unitholders against Pioneer USA, MergerCo, the Partnership, the General Partner and the directors of the General Partner in the Court of Chancery of the State of Delaware (the "Wilson Lawsuit"). The Wilson Lawsuit alleges that the director defendants breached their purported fiduciary obligations to the unitholders by engaging in a process that undervalued the Partnership and which allegedly constitutes gross negligence, recklessness, willful misconduct, bad faith or knowing violations of law. Additionally, the Wilson Lawsuit alleges that the non-director defendants aided and abetted the purported breaches of fiduciary duties of the director defendants. The Wilson Lawsuit seeks the same remedies as the plaintiffs in the Texas State Court Lawsuit and the Federal Lawsuits. As of the date of this Report, the plaintiffs in the Wilson Lawsuit have not joined the memorandum of understanding.
	The Partnership cannot predict the outcome of these or any other lawsuits that might be filed subsequent to the date of the filing of this Report, nor can the Partnership predict the amount of time and expense that will be required to resolve these lawsuits. See Note B for a description of the Merger Agreement.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	The Partnership's income tax provisions and benefits, which were entirely attributable to the Texas Margin tax (which rate currently approximates one percent of the Partnership's taxable income apportioned to Texas), consisted of the following for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
		2013		2012		2013		2012
		(in thousands)
	Current provisions:
	U.S. state	$	13	$	21	$	119	$	105
	Deferred provisions:
	U.S. state	236		90		716		957
		$	249	$	111	$	835	$	1,062
	The Partnership's net deferred tax attributes represented current assets of $96 thousand and $89 thousand as of September 30, 2013 and December 31, 2012, respectively, and noncurrent liabilities of $879 thousand and $156 thousand as of September 30, 2013 and December 31, 2012, respectively. In connection with the Partnership's initial public offering in 2008, the Partnership entered into a tax sharing agreement with Pioneer. Under this agreement, the Partnership pays Pioneer for its share of state and local income and other taxes (currently only the Texas Margin tax) for which the Partnership's results are included in a combined or consolidated tax return filed by Pioneer. The Partnership's share of Texas Margin tax is determined based on a pro forma tax return that includes only the income, deductions, gains, losses and credits of the Partnership as if the Partnership filed a separate return. As of September 30, 2013 and December 31, 2012, the Partnership had $162 thousand and $70 thousand, respectively, of income taxes payable to affiliate in the accompanying consolidated balance sheets, representing amounts due to Pioneer under the tax sharing agreement.

Subsequent_Event

Subsequent Event	9 Months Ended
	Sep. 30, 2013
Subsequent Events [Abstract]	'
Subsequent Event	'
	Subsequent Events
	Distribution declaration. In October 2013, the Partnership declared a cash distribution of $0.52 per common unit for the period from July 1, 2013 to September 30, 2013. The distribution is payable on November 12, 2013 to unitholders of record at the close of business on November 4, 2013. Associated therewith, the Partnership expects to pay $18.6 million of aggregate distributions.
	Merger Agreement. On October 25, 2013, the Partnership entered into an amendment to the Agreement and Plan of Merger with Pioneer, Pioneer USA, MergerCo and the General Partner dated August 9, 2013. Pursuant to the Merger Agreement, MergerCo will merge with and into the Partnership, with the Partnership surviving the Merger, such that following the Merger, the General Partner will remain a wholly-owned subsidiary of Pioneer and the sole general partner of the Partnership, and Pioneer USA will be the sole limited partner of the Partnership. Except for the common units owned by Pioneer, all of the common units outstanding as of the closing of the Merger will be cancelled and, except for the dissenting units, converted into the right to receive 0.2325 of a share of common stock of Pioneer per common unit. The closing of the Merger is subject to the satisfaction of certain closing conditions. See Note B for a description of the Merger Agreement.

Basis_of_Presentation_Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Net Income Per Common Unit	'
	Net income per common unit is calculated by dividing the limited partners' interest in net income (which excludes net income allocable to unvested participating securities) by the weighted average number of common units outstanding.
	The Partnership applies the provisions of Accounting Standards Codification ("ASC") Topic 260 "Earnings Per Share" when determining net income per common unit. Instruments granted in unit-based payment transactions that are determined to be participating securities prior to vesting are included in the net income allocation in computing basic and diluted net income per unit. Participating securities represent unvested unit-based compensation awards that have non-forfeitable distribution rights during their vesting periods, such as the phantom units and restricted units awarded under the Pioneer Southwest Energy Partners L.P. 2008 Long Term Incentive Plan (the "LTIP").
	The Partnership's net income is allocated to partners' equity accounts in accordance with the provisions of the First Amended and Restated Agreement of Limited Partnership of Pioneer Southwest Energy Partners L.P. (the "Partnership Agreement").

Incentive_Plans_Policies

Incentive Plans (Policies)	9 Months Ended
	Sep. 30, 2013
Incentive Plans [Abstract]	'
Unit-based awards	'
	This compensation will be recognized over the remaining vesting periods of the awards, which on a weighted average basis is a period of less than three years.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	'
	The following table presents the Partnership's assets and liabilities that are measured at fair value as of September 30, 2013:
		Fair Value Measurements at the End of the Reporting Period Using
		Quoted Prices in		Significant		Significant		Fair Value at September 30, 2013
		Active  Markets		Other		Unobservable
		for Identical		Observable		Inputs
		Assets		Inputs		(Level 3)
		(Level 1)		(Level 2)
		(in thousands)
	Recurring fair value measurements
	Assets:
	Commodity derivatives	$	—	$	8,293	$	—	$	8,293
	Liabilities:
	Commodity derivatives	—		4,795		—		4,795
	Total recurring fair value measurements	$	—	$	3,498	$	—	$	3,498
Schedule of Fair Value, by Balance Sheet Grouping	'
	The carrying values and fair values of financial instruments that are not recorded at fair value in the accompanying consolidated balance sheets as of September 30, 2013 and December 31, 2012 are as follows:
		September 30, 2013				December 31, 2012
		Carrying		Fair		Carrying		Fair
		Value		Value		Value		Value
		(in thousands)
	Credit facility	$	201,000	$	193,355	$	126,000	$	123,635

Derivative_Financial_Instrumen1

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Schedule of Oil Derivative Contract Volumes and Weighted Average Prices	'
	The following table sets forth the volumes per day in barrels ("BBLs") outstanding as of September 30, 2013 under the Partnership's oil derivative contracts and the weighted average NYMEX prices per BBL for those contracts as of September 30, 2013:
		Three Months Ending			Year Ending
		December 31,			December 31,
		2013			2014
	Collar contracts with short puts:
	Volume (BBLs per day)	—			5,000
	Average price per BBL:
	Ceiling	$	—		$	105.74
	Floor	$	—		$	100
	Short put	$	—		$	80
	Swap contracts:
	Volume (BBLs per day)	4,750			—
	Average price per BBL	$	87.83		$	—
Schedule of Gas Derivative Contract Volumes and Weighted Average Prices	'
	The following table sets forth the volumes in millions of British Thermal Units ("MMBTUs") under outstanding gas derivative contracts and the weighted average index prices per MMBTU for those contracts as of September 30, 2013:
		Three Months Ending December 31,			Year Ending
					December 31,
		2013			2014			2015
	Collar contracts with short puts:
	Volume (MMBTUs per day)	—			—			5,000
	Average price per MMBTU:
	Ceiling	$	—		$	—		$	5
	Floor	$	—		$	—		$	4
	Short put	$	—		$	—		$	3
	Collar contracts:
	Volume (MMBTUs per day)	2,500			—			—
	Average price per MMBTU:
	Ceiling	$	4.5		$	—		$	—
	Floor	$	4		$	—		$	—
	Swap contracts:
	Volume (MMBTUs per day)	2,500			5,000			—
	Average price per MMBTU	$	6.89		$	4		$	—
	Basis swap contracts:
	Permian Basin index swaps - (MMBTUs per day)	2,500			—			—
	Price differential ($/MMBTU)	$	(0.31	)	$	—		$	—
Schedule of Derivative Instruments	'
	The aggregate fair value of the Partnership's derivative instruments that are reported in the consolidated balance sheets consists of the following:
	Fair Value of Derivative Instruments as of September 30, 2013
	Consolidated Balance Sheet Location	Fair			Gross Amounts Offset in the Consolidated Balance Sheet			Net Fair Value Presented in the Consolidated Balance Sheet
		Value
		(in thousands)
	Derivatives not designated as hedging instruments
	Asset Derivatives:
	Derivatives - current	$	6,465		$	(1,227	)	$	5,238
	Derivatives - noncurrent	$	3,071		$	(16	)	3,055
								$	8,293
	Liability Derivatives:
	Derivatives - current	$	6,022		$	(1,227	)	$	4,795
	Derivatives - noncurrent	$	16		$	(16	)	—
								$	4,795
	Fair Value of Derivative Instruments as of December 31, 2012
	Consolidated Balance Sheet Location	Fair			Gross Amounts Offset in the Consolidated Balance Sheet			Net Fair Value Presented in the Consolidated Balance Sheet
		Value
		(in thousands)
	Derivatives not designated as hedging instruments
	Asset Derivatives:
	Derivatives - current	$	4,553		$	—		$	4,553
	Derivatives - noncurrent	$	7,278		$	(51	)	7,227
								$	11,780
	Liability Derivatives:
	Derivatives - current	$	13,390		$	—		$	13,390
	Derivatives - noncurrent	$	201		$	(51	)	150
								$	13,540

Exploratory_Costs_Tables

Exploratory Costs (Tables)	9 Months Ended
	Sep. 30, 2013
Exploratory Cost Disclosure [Abstract]	'
Capitalized Exploratory Well Activity	'
	The following table reflects the Partnership's capitalized exploratory well activity during the three and nine months ended September 30, 2013:
		Three Months Ended			Nine Months Ended
		September 30, 2013			September 30, 2013
		(in thousands)
	Beginning capitalized exploratory costs	$	10,572		$	—
	Additions to exploratory costs pending the determination of proved reserves	5,552			35,225
	Reclassification due to determination of proved reserves	(16,109		)	(35,210		)
	Ending capitalized exploratory costs (a)	$	15		$	15
	__________
	(a)	All capitalized exploratory costs are aged less than one year based on the date drilling was completed.

Incentive_Plans_Tables

Incentive Plans (Tables)	9 Months Ended
	Sep. 30, 2013
Incentive Plans [Abstract]	'
Schedule of Unit-based Awards Activity	'
	The following table reflects the Partnership's outstanding unit-based awards as of September 30, 2013 and the activity related thereto for the nine months ended September 30, 2013:
		Restricted		Phantom
		Units		Units
	Outstanding at beginning of year	7,496		102,644
	Units granted	—		32,242
	Lapse of restrictions	(7,496	)	(35,118	)
	Outstanding at September 30, 2013	—		99,768

Asset_Retirement_Obligations_T

Asset Retirement Obligations (Tables)	9 Months Ended
	Sep. 30, 2013
Asset Retirement Obligation [Abstract]	'
Schedule of Change in Asset Retirement Obligation	'
	The following table summarizes the Partnership's asset retirement obligation activity during the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2013			2012			2013			2012
		(in thousands)
	Beginning asset retirement obligations	$	11,946		$	9,867		$	12,101		$	10,315
	Liabilities settled	(636		)	(576		)	(1,325		)	(1,477		)
	New wells placed on production	168			48			288			123
	Accretion of discount	209			189			623			567
	Ending asset retirement obligations	$	11,687		$	9,528		$	11,687		$	9,528

Related_Party_Transactions_Tab

Related Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2013
Related Party Transactions [Abstract]	'
Schedule of Related Party Transactions	'
	In accordance with standard industry operating agreements and the various agreements entered into between the Partnership and Pioneer, the Partnership incurred the following charges from Pioneer during the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
		2013		2012		2013		2012
		(in thousands)
	Producing well overhead (COPAS) fees	$	3,074	$	2,863	$	9,083	$	8,361
	Payment of lease operating and supervision charges	3,558		2,498		9,548		7,384
	Drilling and completion related charges	11,334		8,546		38,668		28,775
	General and administrative expenses	1,298		1,181		3,648		3,422
	Total	$	19,264	$	15,088	$	60,947	$	47,942

Income_Taxes_Tables

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
Schedule of Components of Income Tax Provisions	'
	The Partnership's income tax provisions and benefits, which were entirely attributable to the Texas Margin tax (which rate currently approximates one percent of the Partnership's taxable income apportioned to Texas), consisted of the following for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
		2013		2012		2013		2012
		(in thousands)
	Current provisions:
	U.S. state	$	13	$	21	$	119	$	105
	Deferred provisions:
	U.S. state	236		90		716		957
		$	249	$	111	$	835	$	1,062

Partnership_And_Nature_Of_Oper1

Partnership And Nature Of Operations (Narrative) (Details)	Sep. 30, 2013
Limited Partner Interest [Member] | Pioneer Natural Resources Co [Member]	'
Noncontrolling Interest [Line Items]	'
Ownership Percentage by Parent (As a Percent)	52.40%
Pioneer Natural Resources Co [Member]	'
Noncontrolling Interest [Line Items]	'
Omnibus Agreement, Number of Counties Within the Southeast Region of New Mexico that Area of Operations is Limited To	8

Basis_of_Presentation_Recent_D

Basis of Presentation Recent Developments (Details) (USD $)	3 Months Ended
	Sep. 30, 2013	Oct. 25, 2013
Variable Interest Entity [Line Items]	'	'
Cash distribution declared per common unit	$0.52	'
Share Per Unit Exchange Ratio	'	0.2325
Cap on Distributions Made to Member or Limited Partner, Per Share	'	$0.52
Limited Partner Interest [Member] | Pioneer Natural Resources Co [Member]	'	'
Variable Interest Entity [Line Items]	'	'
Ownership Percentage by Parent (As a Percent)	52.40%	'

Fair_Value_Measurements_Assets

Fair Value Measurements (Assets and Liabilities Measured At Fair Value on a Recurring Basis) (Details) (Fair Value, Measurements, Recurring [Member], Commodity Derivatives [Member], USD $)	Sep. 30, 2013
In Thousands, unless otherwise specified
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'
Assets:	'
Commodity Derivatives	$0
Liabilities:	'
Commodity Derivatives	0
Recurring Measurements, (Fair Value, Net)	0
Significant Other Observable Inputs (Level 2) [Member]	'
Assets:	'
Commodity Derivatives	8,293
Liabilities:	'
Commodity Derivatives	4,795
Recurring Measurements, (Fair Value, Net)	3,498
Significant Unobservable Inputs (Level 3) [Member]	'
Assets:	'
Commodity Derivatives	0
Liabilities:	'
Commodity Derivatives	0
Recurring Measurements, (Fair Value, Net)	0
Fair Value [Member]	'
Assets:	'
Commodity Derivatives	8,293
Liabilities:	'
Commodity Derivatives	4,795
Recurring Measurements, (Fair Value, Net)	$3,498

Fair_Value_Measurements_Carryi

Fair Value Measurements (Carrying Values and Fair Values of Financial Instruments) (Details) (Significant Other Observable Inputs (Level 2) [Member], USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Carrying Value [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Credit facility	$201,000	$126,000
Fair Value [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Credit facility	$193,355	$123,635

Derivative_Financial_Instrumen2

Derivative Financial Instruments (Schedule of Oil Derivative Contract Volumes And Weighted Average Prices) (Details) (Oil Contracts [Member])	Sep. 30, 2013
	bbl
2014 Collar Contracts With Short Puts [Member]	'
Derivative [Line Items]	'
Volume (BBLs per day)	5,000
Average Price, Ceiling	105.74
Average Price, Floor	100
2014 Collar Contracts With Short Puts [Member] | Short Put [Member]	'
Derivative [Line Items]	'
Average Price, Short Put	80
2013 Swap Contracts [Member]	'
Derivative [Line Items]	'
Volume (BBLs per day)	4,750
Average Price, Fixed	87.83

Derivative_Financial_Instrumen3

Derivative Financial Instruments (Schedule of Gas Derivative Contract Volumes and Weighted Average Prices) (Details) (Gas Contracts [Member])	Sep. 30, 2013
	MMBTU
2015 Collar Contracts With Short Puts [Member]	'
Derivative [Line Items]	'
Volume (MMBTUs per day)	5,000
Average Price, Ceiling	5
Average Price, Floor	4
2015 Collar Contracts With Short Puts [Member] | Short Put [Member]	'
Derivative [Line Items]	'
Average Price, Short Put	3
2013 Collar Contracts [Member]	'
Derivative [Line Items]	'
Volume (MMBTUs per day)	2,500
Average Price, Ceiling	4.5
Average Price, Floor	4
2013 Swap Contracts [Member]	'
Derivative [Line Items]	'
Volume (MMBTUs per day)	2,500
Average Price, Fixed	6.89
2014 Swap Contracts [Member]	'
Derivative [Line Items]	'
Volume (MMBTUs per day)	5,000
Average Price, Fixed	4
2013 Basis Swap Contracts [Member]	'
Derivative [Line Items]	'
Volume (MMBTUs per day)	2,500
Price Differential ($/MMBTU)	-0.31

Derivative_Financial_Instrumen4

Derivative Financial Instruments (Schedule of Derivative Instruments) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Derivative [Line Items]	'	'	'	'	'
Derivative assets, current	$5,238	'	$5,238	'	$4,553
Derivative liabilities, current	4,795	'	4,795	'	13,390
Derivative assets, noncurrent	3,055	'	3,055	'	7,227
Derivative liabilities, noncurrent	0	'	0	'	150
Derivative gains (losses), net	-11,380	-13,592	-7,230	18,176	'
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]	'	'	'	'	'
Derivative [Line Items]	'	'	'	'	'
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	8,293	'	8,293	'	11,780
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	4,795	'	4,795	'	13,540
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Derivative Current [Member]	'	'	'	'	'
Derivative [Line Items]	'	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	6,465	'	6,465	'	4,553
Derivative Liability, Fair Value, Gross Liability	6,022	'	6,022	'	13,390
Derivative Assets and Liabilities Offset In Balance Sheet	-1,227	'	-1,227	'	0
Derivative assets, current	5,238	'	5,238	'	'
Derivative liabilities, current	4,795	'	4,795	'	'
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Derivative Noncurrent [Member]	'	'	'	'	'
Derivative [Line Items]	'	'	'	'	'
Derivative Asset, Fair Value, Gross Asset	3,071	'	3,071	'	7,278
Derivative Liability, Fair Value, Gross Liability	16	'	16	'	201
Derivative Assets and Liabilities Offset In Balance Sheet	-16	'	-16	'	-51
Derivative assets, noncurrent	3,055	'	3,055	'	'
Derivative liabilities, noncurrent	$0	'	$0	'	'

Exploratory_Costs_Schedule_of_

Exploratory Costs (Schedule of Capitalized Exploratory Well Activity) (Details) (USD $)	3 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013
Costs Incurred, Oil and Gas Property Exploration Activities [Line Items]	'	'
Beginning Capitalized Exploratory Costs	$10,572	$0
Additions to Exploratory Costs Pending Determination of Proved Reserves	5,552	35,225
Reclassification Due to Determination of Proved Reserves	-16,109	-35,210
Ending Capitalized Exploratory Costs	$15	$15

LongTerm_Debt_Details

Long-Term Debt (Details) (USD $)	1 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2013	Sep. 30, 2013	Mar. 31, 2012
	Quarters	Revolving Credit Facility [Member]	Revolving Credit Facility [Member]
Debt Instrument [Line Items]	'	'	'
Credit Facility, Maximum Borrowing Capacity	'	'	$300
Outstanding Borrowings Under Credit Facility	'	201	'
Remaining Borrowing Capacity Under Credit Facility	'	$68.60	'
Minimum Hedging Requirement Per Credit Agreement (As a Percent)	50.00%	'	'
Minimum Hedging Requirement Rolling Basis (in Years)	'2 years	'	'
Minimum Hedging Requirement Amended Rolling Basis (in Quarters)	4	'	'

Incentive_Plans_Narrative_Deta

Incentive Plans (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Unit-based compensation expense	$240,000	$287,000	$791,000	$811,000
Unit-based compensation, unvested awards, total compensation expense unrecognized	$1,300,000	'	$1,300,000	'
Maximum [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Unit-based compensation arrangement, award remaining vesting period (in years)	'	'	'3 years	'

Incentive_Plans_Unitbased_awar

Incentive Plans (Unit-based awards) (Details)	9 Months Ended
	Sep. 30, 2013
Restricted Units [Member]	'
Number of Units	'
Outstanding at beginning of year (in units)	7,496
Units granted (in units)	0
Lapse of restrictions (in units)	-7,496
Outstanding at end of year (in units)	0
Phantom Units [Member]	'
Number of Units	'
Outstanding at beginning of year (in units)	102,644
Units granted (in units)	32,242
Lapse of restrictions (in units)	-35,118
Outstanding at end of year (in units)	99,768

Asset_Retirement_Obligations_D

Asset Retirement Obligations (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]	'	'	'	'
Beginning asset retirement obligations	$11,946	$9,867	$12,101	$10,315
Liabilities settled	-636	-576	-1,325	-1,477
New wells placed on production	168	48	288	123
Accretion of discount	209	189	623	567
Ending asset retirement obligations	$11,687	$9,528	$11,687	$9,528

Related_Party_Transactions_Tab1

Related Party Transactions Table (Details) (Pioneer Natural Resources Co [Member], USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Related Party Transaction [Line Items]	'	'	'	'
Related Party Charges	$19,264	$15,088	$60,947	$47,942
Producing well overhead (COPAS) fees [Member]	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Related Party Charges	3,074	2,863	9,083	8,361
Payment of lease operating and supervision charges [Member]	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Related Party Charges	3,558	2,498	9,548	7,384
Drilling and completion related charges [Member]	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Related Party Charges	11,334	8,546	38,668	28,775
General and Administrative Expense [Member]	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Related Party Charges	$1,298	$1,181	$3,648	$3,422

Related_Party_Transactions_Nar

Related Party Transactions (Narrative) (Details) (USD $)

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Phantom units [Member]

Pioneer Natural Resources Co [Member]

Pioneer Natural Resources Co [Member]

General Partner [Member]

General Partner [Member]

General Partner [Member]

General Partner [Member]

General Partner [Member]

General Partner [Member]

General Partner [Member]

General Partner [Member]

Drilling and completion related charges [Member]

Drilling and completion related charges [Member]

General and Administrative Expense [Member]

General and Administrative Expense [Member]

Other miscellaneous items [Member]

Other miscellaneous items [Member]

Midland County [Member]

Phantom units [Member]

Phantom units [Member]

Phantom units [Member]

Phantom units [Member]

Pioneer Natural Resources Co [Member]

Pioneer Natural Resources Co [Member]

Pioneer Natural Resources Co [Member]

Pioneer Natural Resources Co [Member]

Pioneer Natural Resources Co [Member]

Pioneer Natural Resources Co [Member]

Pioneer Natural Resources Co [Member]

acre

Related Party Transaction [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Due from Affiliates

$391,000

$0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Due to affiliates

0

1,277,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Payable to related party, current

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,300,000

1,400,000

40,000

106,000

'

Receivable from related party, current

'

'

'

'

'

'

'

'

'

'

'

'

'

1,729,000

266,000

'

'

'

'

'

Income taxes payable to affiliate

'

'

'

162,000

70,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gas and Oil Area, Undeveloped, Net

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,200

Undivided Interest in Leases, Assigned from Related Party as Consideration of Related Party's Acquisition Costs, Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

94.00%

Acquisition Cost of Oil and Gas Property, Pro Rata Share

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,500,000

Restricted common units to directors, vested in period, total cash value

'

'

'

'

'

0

50,000

74,000

147,000

'

'

'

'

'

'

'

'

'

'

'

Units granted (in units)

'

'

32,242

'

'

'

'

'

'

'

'

32,242

37,487

'

'

'

'

'

'

'

Award remaining vesting period (in years)

'

'

'

'

'

'

'

'

'

'

'

'3 years

'

'

'

'

'

'

'

'

General and administrative expenses from transactions with related party

'

'

'

'

'

'

'

'

'

240,000

237,000

717,000

664,000

'

'

'

'

'

'

'

General and administrative expenses from transactions with related party, noncash

'

'

'

'

'

'

'

'

'

$231,000

$228,000

$690,000

$639,000

'

'

'

'

'

'

'

Income_Taxes_Schedule_of_Incom

Income Taxes (Schedule of Income Tax Provisions) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Current:	'	'	'	'
U.S. State	$13	$21	$119	$105
Deferred:	'	'	'	'
U.S. State	236	90	716	957
Income tax provision	$249	$111	$835	$1,062

Income_Taxes_Narrative_Details

Income Taxes (Narrative) (Details) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Income Tax [Line Items]	'	'
Deferred tax assets, current	$96	$89
Deferred tax liabilities, noncurrent	879	156
Pioneer Natural Resources Co [Member]	'	'
Income Tax [Line Items]	'	'
Income taxes payable to affiliate	$162	$70
Texas [Member]	'	'
Income Tax [Line Items]	'	'
Margin Tax Rate (As a Percent)	1.00%	'

Subsequent_Event_Details

Subsequent Event (Details) (USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Oct. 25, 2013
Subsequent Event [Line Items]	'	'
Cash distribution declared per common unit	$0.52	'
Share Per Unit Exchange Ratio	'	0.2325
Subsequent Event [Member]	'	'
Subsequent Event [Line Items]	'	'
Share Per Unit Exchange Ratio	'	0.2325
Subsequent Event [Member] | Cash Distribution [Member]	'	'
Subsequent Event [Line Items]	'	'
Cash distribution declared per common unit	$0.52	'
Aggregate distributions to be paid	$18.60	'