Western Midstream Partners 10-Q 6 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	4-May-15
Document And Entity Information [Abstract]
Trading Symbol	WES
Entity Registrant Name	Western Gas Partners LP
Entity Central Index Key	1414475
Document Type	10-Q
Document Period End Date	31-Mar-15
Amendment Flag	FALSE
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Units Outstanding		128,466,997

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Revenues
Total revenues	$375,094		$293,717	[1]
Equity income, net	18,220	[2],[3],[4]	9,251	[1],[2],[3],[4]
Operating expenses
Cost of product	137,920	[5]	94,376	[1],[5]
Operation and maintenance	56,149	[5]	44,577	[1],[5]
General and administrative	10,512	[5]	8,904	[1],[5]
Property and other taxes	8,523		7,234	[1]
Depreciation, amortization and impairments	70,292		42,085	[1]
Total operating expenses	283,396		197,176	[1]
Operating income	109,918		105,792	[1]
Interest income - affiliates	4,225	[6]	4,225	[1],[6]
Interest expense	-22,960	[7]	-13,961	[1],[7]
Other income (expense), net	71		477	[1]
Income before income taxes	91,254		96,533	[1]
Income tax (benefit) expense	4,460		1,785	[1]
Net income	86,794		94,748	[1]
Net income attributable to noncontrolling interests	3,226		3,692	[1]
Net income attributable to Western Gas Partners, LP	83,568		91,056	[1]
Limited partners' interest in net income:
Pre-acquisition net (income) loss allocated to Anadarko	-1,742		-2,665	[1]
General partner interest in net (income) loss	-41,993	[8]	-24,834	[1],[8]
Limited partners' interest in net income	39,833	[8]	63,557	[1],[8]
Net income per common unit - basic	$0.26	[9]	$0.54	[1],[9]
Net income per common unit - diluted	$0.26	[10],[9]	$0.54	[1],[10],[9]
Affiliated Entity [Member]
Revenues
Gathering, processing and transportation of natural gas and natural gas liquids	128,309		92,683	[1]
Natural gas, natural gas liquids and drip condensate sales	117,236		121,585	[1]
Other	170		728	[1]
Total revenues	245,715		214,996	[1]
Operating expenses
Cost of product	42,407		18,356
Operation and maintenance	15,376	[11]	12,551	[11]
General and administrative	7,566	[12]	7,303	[12]
Total operating expenses	65,349		38,210
Interest expense	-1,420	[13]	0	[13]
Third Parties [Member]
Revenues
Gathering, processing and transportation of natural gas and natural gas liquids	81,535		61,814	[1]
Natural gas, natural gas liquids and drip condensate sales	46,932		16,064	[1]
Other	912		843	[1]
Total revenues	129,379		78,721	[1]
Operating expenses
Interest expense	($21,540)		($13,961)
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[2]	Income earned from equity investments is classified as affiliate. See Note 1.
[3]	Represents amounts earned or incurred on and subsequent to the date of acquisition of the Partnership assets, as well as amounts earned or incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets, recognized under gathering, treating or processing agreements, and purchase and sale agreements.
[4]	Income earned on, distributions from and contributions to equity investments are classified as affiliate. See Note 1.
[5]	Cost of product includes product purchases from Anadarko (as defined in Note 1) of $42.4 million and $18.4 million for the three months ended March 31, 2015 and 2014, respectively. Operation and maintenance includes charges from Anadarko of $15.4 million and $12.6 million for the three months ended March 31, 2015 and 2014, respectively. General and administrative includes charges from Anadarko of $7.6 million and $7.3 million for the three months ended March 31, 2015 and 2014, respectively. See Note 5.
[6]	Represents interest income recognized on the note receivable from Anadarko.
[7]	Includes affiliate (as defined in Note 1) interest expense of $1.4 million and zero for the three months ended March 31, 2015 and 2014, respectively. See Note 2 and Note 9.
[8]	Represents net income earned on and subsequent to the date of acquisition of the Partnership assets (as defined in Note 1). See Note 4.
[9]	See Note 4 for the calculation of net income per unit.
[10]	Inclusion of 10,938,232 Class C units in the calculation would have had an anti-dilutive effect.
[11]	Represents expenses incurred on and subsequent to the date of the acquisition of the Partnership assets, as well as expenses incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets.
[12]	Represents general and administrative expense incurred on and subsequent to the date of the Partnership’s acquisition of the Partnership assets, as well as a management services fee for reimbursement of expenses incurred by Anadarko for periods prior to the acquisition of the Partnership assets by the Partnership. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see WES LTIP and WGP LTIP and Anadarko Incentive Plans within this Note 5).
[13]	For the three months ended March 31, 2015, includes accretion expense recognized on the Deferred purchase price obligation - Anadarko for the acquisition of DBJV (see Note 2 and Note 9).

Consolidated_Statements_of_Inc1

Consolidated Statements of Income (Parenthetical) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Cost of product	$137,920	[1]	$94,376	[1],[2]
Operation and maintenance	56,149	[1]	44,577	[1],[2]
General and administrative	10,512	[1]	8,904	[1],[2]
Interest expense	22,960	[3]	13,961	[2],[3]
Affiliated Entity [Member]
Cost of product	42,407		18,356
Operation and maintenance	15,376	[4]	12,551	[4]
General and administrative	7,566	[5]	7,303	[5]
Interest expense	$1,420	[6]	$0	[6]
[1]	Cost of product includes product purchases from Anadarko (as defined in Note 1) of $42.4 million and $18.4 million for the three months ended March 31, 2015 and 2014, respectively. Operation and maintenance includes charges from Anadarko of $15.4 million and $12.6 million for the three months ended March 31, 2015 and 2014, respectively. General and administrative includes charges from Anadarko of $7.6 million and $7.3 million for the three months ended March 31, 2015 and 2014, respectively. See Note 5.
[2]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[3]	Includes affiliate (as defined in Note 1) interest expense of $1.4 million and zero for the three months ended March 31, 2015 and 2014, respectively. See Note 2 and Note 9.
[4]	Represents expenses incurred on and subsequent to the date of the acquisition of the Partnership assets, as well as expenses incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets.
[5]	Represents general and administrative expense incurred on and subsequent to the date of the Partnership’s acquisition of the Partnership assets, as well as a management services fee for reimbursement of expenses incurred by Anadarko for periods prior to the acquisition of the Partnership assets by the Partnership. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see WES LTIP and WGP LTIP and Anadarko Incentive Plans within this Note 5).
[6]	For the three months ended March 31, 2015, includes accretion expense recognized on the Deferred purchase price obligation - Anadarko for the acquisition of DBJV (see Note 2 and Note 9).

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2015		Dec. 31, 2014
Current assets
Cash and cash equivalents	$58,639,000		$67,054,000	[1]
Accounts receivable, net	144,218,000	[2]	109,243,000	[1],[2]
Other current assets	10,480,000	[3]	10,067,000	[1],[3]
Total current assets	213,337,000		186,364,000	[1]
Note receivable - Anadarko	260,000,000		260,000,000	[1]
Property, plant and equipment
Cost	5,814,914,000		5,626,650,000	[1]
Less accumulated depreciation	1,103,643,000		1,055,207,000	[1]
Net property, plant and equipment	4,711,271,000		4,571,443,000	[1]
Goodwill	393,035,000		389,087,000	[1]
Other intangible assets	853,449,000		884,857,000	[1]
Equity investments	635,920,000		634,492,000	[1]
Other assets	27,616,000		28,289,000	[1]
Total assets	7,094,628,000		6,954,532,000	[1]
Current liabilities
Accounts and natural gas imbalance payables	51,015,000	[4]	54,232,000	[1],[4]
Accrued ad valorem taxes	19,725,000		14,812,000	[1]
Accrued liabilities	171,609,000		170,789,000	[1]
Total current liabilities	242,349,000		239,833,000	[1]
Long-term debt	2,532,995,000		2,422,954,000	[1]
Deferred income taxes	7,802,000		45,656,000	[1]
Asset retirement obligations and other	114,766,000		111,714,000	[1]
Deferred purchase price obligation - Anadarko	175,696,000	[5]	0	[1],[5]
Total long-term liabilities	2,831,259,000		2,580,324,000	[1]
Total liabilities	3,073,608,000		2,820,157,000	[1]
Equity and partners' capital
General partner units (2,583,068 units issued and outstanding at March 31, 2015, and December 31, 2014)	111,071,000		105,725,000	[1]
Net investment by Anadarko	0		122,509,000	[1]
Total partners' capital	3,951,474,000		4,064,905,000	[1]
Noncontrolling interest	69,546,000		69,470,000	[1]
Total equity and partners' capital	4,021,020,000		4,134,375,000	[1]
Total liabilities, equity and partners' capital	7,094,628,000		6,954,532,000	[1]
Common Units [Member]
Equity and partners' capital
Common units (128,177,253 and 127,695,130 units issued and outstanding at March 31, 2015, and December 31, 2014, respectively) and Class C Units (10,959,564 and 10,913,853 units issued and outstanding at March 31, 2015, and December 31, 2014, respectively)	3,116,504,000		3,119,714,000	[1]
Class C Units [Member]
Equity and partners' capital
Common units (128,177,253 and 127,695,130 units issued and outstanding at March 31, 2015, and December 31, 2014, respectively) and Class C Units (10,959,564 and 10,913,853 units issued and outstanding at March 31, 2015, and December 31, 2014, respectively)	$723,899,000		$716,957,000	[1]
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[2]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $38.9 million and $64.7 million as of March 31, 2015, and December 31, 2014, respectively.
[3]	Other current assets includes natural gas imbalance receivables from affiliates of zero and $0.2 million as of March 31, 2015, and December 31, 2014, respectively.
[4]	Accounts and natural gas imbalance payables includes amounts payable to affiliates of zero and $0.1 million as of March 31, 2015, and December 31, 2014, respectively.
[5]	See Note 2.

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, except Share data, unless otherwise specified
General partner units issued	2,583,068		2,583,068
General partner units outstanding	2,583,068		2,583,068
Accounts receivable, net	$144,218	[1]	$109,243	[1],[2]
Other current assets	10,480	[3]	10,067	[2],[3]
Accounts and natural gas imbalance payables	51,015	[4]	54,232	[2],[4]
Common Units [Member]
Units issued	128,177,253		127,695,130
Units outstanding	128,177,253		127,695,130
Class C Units [Member]
Units issued	10,959,564		10,913,853
Units outstanding	10,959,564		10,913,853
Affiliated Entity [Member]
Accounts receivable, net	38,900		64,700
Other current assets	0		200
Accounts and natural gas imbalance payables	$0		$100
[1]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $38.9 million and $64.7 million as of March 31, 2015, and December 31, 2014, respectively.
[2]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[3]	Other current assets includes natural gas imbalance receivables from affiliates of zero and $0.2 million as of March 31, 2015, and December 31, 2014, respectively.
[4]	Accounts and natural gas imbalance payables includes amounts payable to affiliates of zero and $0.1 million as of March 31, 2015, and December 31, 2014, respectively.

Consolidated_Statement_of_Equi

Consolidated Statement of Equity and Partners' Capital (USD $)		Total	Net Investment by Anadarko [Member]	Common Units [Member]	Class C Units [Member]	General Partner Units [Member]	Noncontrolling Interest [Member]
In Thousands
Balance at Dec. 31, 2014	[1]	$4,134,375	$122,509	$3,119,714	$716,957	$105,725	$69,470
Net income (loss)		86,794	1,742	36,576	3,257	41,993	3,226
Issuance of common units, net of offering expenses		31,044		31,044
Amortization of beneficial conversion feature of Class C units		0		-3,685	3,685
Distributions to noncontrolling interest owner		-3,150					-3,150
Distributions to unitholders		-126,044		-89,387		-36,657
Acquisitions from affiliates		-174,276	-196,191	21,915
Contributions of equity-based compensation from Anadarko		845		828		17
Net pre-acquisition contributions from (distributions to) Anadarko		30,096	30,096
Net distributions to Anadarko of other assets		-348		-341		-7
Elimination of net deferred tax liabilities		41,844	41,844
Other		-160		-160
Balance at Mar. 31, 2015		$4,021,020	$0	$3,116,504	$723,899	$111,071	$69,546
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Cash flows from operating activities
Net income	$86,794		$94,748	[1]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and impairments	70,292		42,085	[1]
Non-cash equity-based compensation expense	1,035		1,150	[1]
Deferred income taxes	3,758		993	[1]
Accretion and amortization of long-term obligations, net	2,112		680	[1]
Equity income, net	-18,220	[2],[3],[4]	-9,251	[1],[2],[3],[4]
Distributions from equity investment earnings	18,706	[4]	10,269	[1],[4]
Changes in assets and liabilities:
(Increase) decrease in accounts receivable, net	-17,672		-15,439	[1]
Increase (decrease) in accounts and natural gas imbalance payables and accrued liabilities, net	10,451		6,706	[1]
Change in other items, net	-1,220		1,878	[1]
Net cash provided by operating activities	156,036		133,819	[1]
Cash flows from investing activities
Capital expenditures	-200,940		-199,150	[1]
Investments in equity affiliates	-4,878		-28,462	[1]
Distributions from equity investments in excess of cumulative earnings	2,964	[4],[5]	2,044	[1],[4]
Net cash used in investing activities	-203,960		-586,520	[1]
Cash flows from financing activities
Borrowings, net of debt issuance costs	140,000		917,742	[1]
Repayments of debt	-30,000		-430,000	[1]
Increase (decrease) in outstanding checks	-2,468		1,928	[1]
Proceeds from the issuance of common and general partner units, net of offering expenses	31,075		18,289	[1]
Distributions to unitholders	-126,044		-92,609	[1]
Distributions to noncontrolling interest owner	-3,150		-4,124	[1]
Net contributions from Anadarko	30,096		23,838	[1]
Net cash provided by financing activities	39,509		435,064	[1]
Net increase (decrease) in cash and cash equivalents	-8,415		-17,637	[1]
Cash and cash equivalents at beginning of period	67,054	[1]	100,728	[1]
Cash and cash equivalents at end of period	58,639		83,091	[1]
Supplemental disclosures
Net distributions to (contributions from) Anadarko of other assets	348		-43	[1]
Interest paid, net of capitalized interest	17,594		14,106	[1]
Taxes paid (reimbursements received)	-138		-340	[1]
Affiliated Entity [Member]
Cash flows from investing activities
Acquisitions	-1,128		-360,952	[1]
Cash flows from financing activities
Distributions to unitholders	-71,695	[6]	-51,882	[6]
Third Parties [Member]
Cash flows from investing activities
Proceeds from the sale of assets to third parties	22		0	[1]
Delaware Basin JV Gathering LLC [Member]
Cash flows from operating activities
Net income			3,621
Adjustments to reconcile net income to net cash provided by operating activities:
Equity income, net			0
Supplemental disclosures
Acquisition of DBJV from Anadarko	$174,276	[7]	$0	[7]
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[2]	Income earned from equity investments is classified as affiliate. See Note 1.
[3]	Represents amounts earned or incurred on and subsequent to the date of acquisition of the Partnership assets, as well as amounts earned or incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets, recognized under gathering, treating or processing agreements, and purchase and sale agreements.
[4]	Income earned on, distributions from and contributions to equity investments are classified as affiliate. See Note 1.
[5]	Distributions in excess of cumulative earnings, classified as investing cash flows in the consolidated statements of cash flows, is calculated on an individual investment basis.
[6]	Represents distributions paid under the partnership agreement (see Note 3 and Note 4).
[7]	See Note 2.

Description_of_Business_and_Ba

Description of Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Description of Business and Basis of Presentation	1.  DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION
	General. Western Gas Partners, LP is a growth-oriented Delaware master limited partnership formed by Anadarko Petroleum Corporation in 2007 to acquire, own, develop and operate midstream energy assets.
	For purposes of these consolidated financial statements, the “Partnership” refers to Western Gas Partners, LP and its subsidiaries. The Partnership’s general partner, Western Gas Holdings, LLC (the “general partner” or “GP”), is owned by Western Gas Equity Partners, LP (“WGP”), a Delaware master limited partnership formed by Anadarko Petroleum Corporation in September 2012 to own the Partnership’s general partner, as well as a significant limited partner interest in the Partnership (see Western Gas Equity Partners, LP below). Western Gas Equity Holdings, LLC is WGP’s general partner and is a wholly owned subsidiary of Anadarko Petroleum Corporation. “Anadarko” refers to Anadarko Petroleum Corporation and its subsidiaries, excluding the Partnership and the general partner, and “affiliates” refers to subsidiaries of Anadarko, excluding the Partnership, and includes equity interests in Fort Union Gas Gathering, LLC (“Fort Union”), White Cliffs Pipeline, LLC (“White Cliffs”), Rendezvous Gas Services, LLC (“Rendezvous”), Enterprise EF78 LLC (the “Mont Belvieu JV”), Texas Express Pipeline LLC (“TEP”), Texas Express Gathering LLC (“TEG”) and Front Range Pipeline LLC (“FRP”). The interests in TEP, TEG and FRP are referred to collectively as the “TEFR Interests.” “Equity investment throughput” refers to the Partnership’s 14.81% share of average Fort Union throughput and 22% share of average Rendezvous throughput, but excludes throughput measured in barrels, consisting of the Partnership’s 10% share of average White Cliffs throughput, 25% share of average Mont Belvieu JV throughput, 20% share of average TEP and TEG throughput and 33.33% share of average FRP throughput. The “DJ Basin complex” refers to the Platte Valley system, Wattenberg system and Lancaster plant, all of which were combined into a single complex in the first quarter of 2014. The “MGR assets” include the Red Desert complex, the Granger straddle plant and the 22% interest in Rendezvous.
	The Partnership is engaged in the business of gathering, processing, compressing, treating and transporting natural gas, condensate, NGLs and crude oil for Anadarko, as well as for third-party producers and customers. As of March 31, 2015, the Partnership’s assets and investments accounted for under the equity method consisted of the following:
		Owned and	Operated	Non-Operated	Equity Interests
		Operated	Interests	Interests
	Natural gas gathering systems	14	2	5	2
	Natural gas treating facilities	8	5	—	1
	Natural gas processing facilities	13	3	—	2
	NGL pipelines	3	—	—	3
	Natural gas pipelines	4	—	—	—
	Oil pipelines	1	—	—	1
	These assets and investments are located in the Rocky Mountains (Colorado, Utah and Wyoming), the Mid-Continent (Kansas and Oklahoma), North-central Pennsylvania and Texas. The Partnership is constructing Train II at the Lancaster plant (located at the DJ Basin complex) with operations expected to commence in the second quarter of 2015. In addition, the Partnership is preparing for construction of Train IV at the DBM complex (see Note 2), with operations expected to commence in the first quarter of 2016. The Partnership has also made progress payments towards the construction of another cryogenic unit at the DBM complex (Train V), with an expected in-service date of mid-2016.
	1.  DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (CONTINUED)
	Western Gas Equity Partners, LP. WGP owns the following types of interests in the Partnership: (i) the general partner interest and all of the incentive distribution rights (“IDRs”) in the Partnership, both owned through WGP’s 100% ownership of the Partnership’s general partner and (ii) a significant limited partner interest (see Holdings of Partnership equity in Note 4). WGP has no independent operations or material assets other than its partnership interests in the Partnership.
	Basis of presentation. The consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”). The consolidated financial statements include the accounts of the Partnership and entities in which it holds a controlling financial interest. All significant intercompany transactions have been eliminated. Investments in non-controlled entities over which the Partnership exercises significant influence are accounted for under the equity method. The Partnership proportionately consolidates its 33.75% share of the assets, liabilities, revenues and expenses attributable to the Non-Operated Marcellus Interest systems and Anadarko-Operated Marcellus Interest systems and its 50% share of the assets, liabilities, revenues and expenses attributable to the Newcastle system and the DBJV system (see Note 2) in the accompanying consolidated financial statements.
	In preparing financial statements in accordance with GAAP, management makes informed judgments and estimates that affect the reported amounts of assets, liabilities, revenues and expenses. Management evaluates its estimates and related assumptions regularly, using historical experience and other methods considered reasonable. Changes in facts and circumstances or additional information may result in revised estimates and actual results may differ from these estimates. Effects on the business, financial condition and results of operations resulting from revisions to estimates are recognized when the facts that give rise to the revisions become known. The information furnished herein reflects all normal recurring adjustments which are, in the opinion of management, necessary for a fair presentation of the consolidated financial statements, and certain prior-period amounts have been reclassified to conform to the current-year presentation.
	Certain information and note disclosures commonly included in annual financial statements have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Accordingly, the accompanying consolidated financial statements and notes should be read in conjunction with the Partnership’s 2014 Form 10-K, as filed with the SEC on February 26, 2015. Management believes that the disclosures made are adequate to make the information not misleading.
	Presentation of Partnership assets. The term “Partnership assets” refers to the assets owned and interests accounted for under the equity method (see Note 7) by the Partnership as of March 31, 2015. Because Anadarko controls the Partnership through its ownership and control of WGP, which owns the Partnership’s entire general partner interest, each acquisition of Partnership assets from Anadarko has been considered a transfer of net assets between entities under common control. As such, the Partnership assets acquired from Anadarko were initially recorded at Anadarko’s historic carrying value, which did not correlate to the total acquisition price paid by the Partnership. Further, after an acquisition of Partnership assets from Anadarko, the Partnership may be required to recast its financial statements to include the activities of such Partnership assets from the date of common control. See Note 2.
	For those periods requiring recast, the consolidated financial statements for periods prior to the Partnership’s acquisition of the Partnership assets from Anadarko have been prepared from Anadarko’s historical cost-basis accounts and may not necessarily be indicative of the actual results of operations that would have occurred if the Partnership had owned the Partnership assets during the periods reported. Net income attributable to the Partnership assets acquired from Anadarko for periods prior to the Partnership’s acquisition of the Partnership assets is not allocated to the limited partners.
	1.  DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (CONTINUED)
	Recently issued accounting standards. The Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2015-06, Earnings Per Share (Topic - 260)—Effects on Historical Earnings per Unit of Master Limited Partnership Dropdown Transactions. This ASU contains guidance that addresses the historical earnings per unit presentation for master limited partnerships that apply the two-class method of calculating earnings per unit. When a general partner transfers or “drops down” net assets to a master limited partnership the transactions is accounted for as a transaction between entities under common control and the statements of operations are adjusted retrospectively to reflect the transaction. This ASU specifies that the historical earnings (losses) of a transferred business before the date of a dropdown transaction should be allocated entirely to the general partner, and the previously reported earnings per unit of the limited partners should not change as a result of the dropdown transaction. The ASU also requires additional 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. This ASU is effective for annual and interim periods beginning in 2016 and is required to be adopted using a retrospective approach, with early adoption permitted. The Partnership believes it is currently in compliance with this ASU, but will continue to evaluate the impact of the adoption of this ASU on its consolidated financial statements.
	The FASB issued ASU 2015-03, Interest—Imputation of Interest (Subtopic 853-30)—Simplifying the Presentation of Debt Issuance Costs. This ASU will simplify the presentation of debt issuance costs by requiring such costs to be presented in the balance sheet as a reduction from the corresponding debt liability rather than as an asset. This ASU is effective for annual and interim periods beginning in 2016 and is required to be adopted using a retrospective approach, with early adoption permitted. The Partnership is considering the alternatives for timing of adoption.
	The FASB issued ASU 2015-02, Consolidation—Amendments to the Consolidation Analysis. This ASU will simplify existing requirements by reducing the number of consolidation models and placing more emphasis on risk of loss when determining a controlling financial interest. The provisions will affect how limited partnerships and similar entities are assessed for consolidation, including the elimination of the presumption that a general partner should consolidate a limited partnership. This ASU is effective for annual and interim periods beginning in 2016 and is required to be adopted using a retrospective or modified retrospective approach, with early adoption permitted. The Partnership is evaluating the impact of the adoption of this ASU on its consolidated financial statements.
	The FASB issued ASU 2014-09, Revenue from Contracts with Customers. This ASU supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and industry-specific guidance in Subtopic 932-605, Extractive Activities—Oil and Gas—Revenue Recognition, and requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration the entity expects to be entitled to in exchange for those goods or services. This ASU is effective for annual and interim periods beginning in 2017 and is required to be adopted using one of two retrospective application methods, with no early adoption permitted. The Partnership is evaluating the impact of the adoption of this ASU on its consolidated financial statements.

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2015
Business Combinations [Abstract]
Acquisitions	2.  ACQUISITIONS
	The following table presents the acquisitions completed by the Partnership during 2015 and 2014, and identifies the funding sources for such acquisitions:
	thousands except unit and percent amounts		Acquisition		Percentage			Deferred Purchase Price Obligation - Anadarko			Borrowings		Cash		Common	Class C Units Issued to Anadarko
			Date		Acquired								On Hand		Units Issued to Anadarko
	TEFR Interests (1)		3/3/14		Various (1)			$	—		$	350,000	$	6,250	308,490	—
	DBM (2)		11/25/14		100	%		—			475,000		298,327		—	10,913,853
	DBJV system (3)		3/2/15		50	%		174,276			—		—		—	—
	(1)	The Partnership acquired a 20% interest in each of TEG and TEP and a 33.33% interest in FRP from Anadarko. These assets gather and transport NGLs primarily from the Anadarko and Denver-Julesburg (“DJ”) Basins. The interests in these entities are accounted for under the equity method of accounting. In connection with the issuance of the common units, the Partnership’s general partner purchased 6,296 general partner units in exchange for the general partner’s proportionate capital contribution of $0.4 million.
	(2)	The Partnership acquired Nuevo Midstream, LLC (“Nuevo”) from a third party. Following the acquisition, the Partnership changed the name of Nuevo to Delaware Basin Midstream, LLC (“DBM”). The assets acquired include cryogenic processing plants, a gas gathering system, and related facilities and equipment, which are collectively referred to as the “DBM complex” and serve production from Reeves, Loving and Culberson Counties, Texas and Eddy and Lea Counties, New Mexico.
	(3)	The Partnership acquired Anadarko’s interest in Delaware Basin JV Gathering LLC (“DBJV”), which owns a 50% interest in a gathering system and related facilities (the “DBJV system”). The DBJV system is located in the Delaware Basin in Loving, Ward, Winkler and Reeves Counties, Texas. The Partnership will make a cash payment on March 31, 2020, to Anadarko as consideration for the acquisition of DBJV. The Partnership currently estimates the future payment will be $282.8 million, the net present value of which was $174.3 million as of the acquisition date. See Deferred purchase price obligation - Anadarko below.
	DBJV acquisition. Because the acquisition of DBJV was a transfer of net assets between entities under common control, the Partnership’s historical financial statements previously filed with the SEC have been recast in this Form 10-Q to include the results attributable to the DBJV system as if the Partnership owned DBJV for all periods presented. The consolidated financial statements for periods prior to the Partnership’s acquisition of DBJV have been prepared from Anadarko’s historical cost-basis accounts and may not necessarily be indicative of the actual results of operations that would have occurred if the Partnership had owned DBJV during the periods reported.
	The following table presents the impact of the DBJV system on revenue, equity income, net and net income as presented in the Partnership’s historical consolidated statements of income:
			Three Months Ended March 31, 2014
	thousands		Partnership Historical				DBJV System			Combined
	Revenues		$	279,457			$	14,260		$	293,717
	Equity income, net		9,251				—			9,251
	Net income		91,127				3,621			94,748
	Deferred purchase price obligation - Anadarko. The consideration to be paid by the Partnership for the acquisition of DBJV consists of a cash payment to Anadarko due on March 31, 2020. The cash payment will be equal to eight multiplied by (a) the average of the Partnership’s share in the Net Earnings (see definition below) of the DBJV system for the calendar years 2018 and 2019, less (b) the Partnership’s share of all capital expenditures incurred for the DBJV system between March 1, 2015, and February 29, 2020. Net Earnings is defined as all revenues less cost of product, operating expenses and property taxes, in each case attributable to the DBJV system on an accrual basis. As of the acquisition date, the estimated future payment obligation was $282.8 million, which had a net present value of $174.3 million, using a discount rate of 10%. As of March 31, 2015, the net present value of this obligation was $175.7 million and has been recorded on the consolidated balance sheet under Deferred purchase price obligation - Anadarko. Accretion expense for the three months ended March 31, 2015, was $1.4 million and has been recorded as a charge to interest expense. The fair value measurement was calculated using Level 3 inputs, which consisted of management’s estimate of the Partnership’s share of forecasted Net Earnings and capital expenditures for the DBJV system.
	2.  ACQUISITIONS (CONTINUED)
	DBM acquisition. The DBM acquisition has been accounted for under the acquisition method of accounting. The assets acquired and liabilities assumed in the DBM acquisition were recorded in the consolidated balance sheet at their estimated fair values as of the acquisition date. Results of operations attributable to the DBM acquisition were included in the Partnership’s consolidated statement of income beginning on the acquisition date in the fourth quarter of 2014.
	The following is the preliminary allocation of the purchase price as of March 31, 2015, including $3.5 million of post-closing purchase price adjustments, to the assets acquired and liabilities assumed in the DBM acquisition as of the acquisition date, pending final review of support related to the acquired entity’s assets:
	thousands
	Current assets		$	63,020
	Property, plant and equipment		467,171
	Goodwill		282,999
	Other intangible assets		811,048
	Accounts payables		(17,679		)
	Accrued liabilities		(38,684		)
	Deferred income taxes		(1,342		)
	Asset retirement obligations and other		(9,060		)
	Total purchase price		$	1,557,473
	The purchase price allocation is based on an assessment of the fair value of the assets acquired and liabilities assumed in the DBM acquisition using inputs that are not observable in the market and thus represent Level 3 inputs. The fair values of the processing plants, gathering system, and related facilities and equipment are based on market and cost approaches. The fair value of the intangible assets was determined using an income approach. Deferred taxes represent the tax effects of differences in the tax basis and acquisition-date fair value of the assets acquired and liabilities assumed.

Partnership_Distributions

Partnership Distributions	3 Months Ended
	Mar. 31, 2015
Distributions Made to Members or Limited Partners [Abstract]
Partnership Distributions	3.  PARTNERSHIP DISTRIBUTIONS
	The partnership agreement of Western Gas Partners, LP requires the Partnership to distribute all of its available cash (as defined in the partnership agreement) to unitholders of record on the applicable record date within 45 days of the end of each quarter. The Board of Directors of the general partner declared the following cash distributions to the Partnership’s common and general partner unitholders for the periods presented:
	thousands except per-unit amounts		Total Quarterly		Total Quarterly		Date of
	Quarters Ended		Distribution		Cash Distribution		Distribution
			per Unit
	31-Mar-14		$	0.625	$	98,749	May 2014
	March 31, 2015 (1)		0.725		133,203		May 2015
	(1)	On April 20, 2015, the Board of Directors of the Partnership’s general partner declared a cash distribution to the Partnership’s unitholders of $0.725 per unit, or $133.2 million in aggregate, including incentive distributions, but excluding distributions on Class C units (see Class C unit distributions below). The cash distribution is payable on May 13, 2015, to unitholders of record at the close of business on April 30, 2015.
	3.  PARTNERSHIP DISTRIBUTIONS (CONTINUED)
	Class C unit distributions. The Class C units receive quarterly distributions at a rate equivalent to the Partnership’s common units. The distributions are paid in the form of additional Class C units (“PIK Class C units”) until the end of 2017 (unless earlier converted), and the Class C units are disregarded with respect to distributions of the Partnership’s available cash until they are converted to common units. The number of additional PIK Class C units to be issued in connection with a distribution payable on the Class C units is determined by dividing the corresponding distribution attributable to the Class C units by the volume-weighted-average price of the Partnership’s common units for the ten days immediately preceding the payment date for the common unit distribution, less a 6% discount. The Partnership records the PIK Class C unit distributions at fair value at the time of issuance. This Level 2 fair value measurement uses the Partnership’s unit price as a significant input in the determination of the fair value. On February 12, 2015, the Partnership issued 45,711 PIK Class C units to APC Midstream Holdings, LLC (“AMH”), a subsidiary of Anadarko and the holder of the Class C units, based on the $0.700 common unit distribution for the fourth quarter of 2014, with an implied fair value of $3.1 million. The Class C unit distribution was prorated for the 37-day period the Class C units were outstanding during the fourth quarter of 2014.

Equity_and_Partners_Capital

Equity and Partners' Capital	3 Months Ended
	Mar. 31, 2015
Partners' Capital Notes [Abstract]
Equity and Partners' Capital	4.  EQUITY AND PARTNERS’ CAPITAL
	Equity offerings. The Partnership completed the following public offerings of its common units during 2015 and 2014, including through its Continuous Offering Programs (“COP”):
	thousands except unit and per-unit amounts		Common Units Issued			GP Units Issued (1)			Price Per			Underwriting		Net
									Unit			Discount and		Proceeds
												Other Offering
												Expenses
	$125.0 million COP (2)		1,133,384			23,132			$	73.48		$	1,738	$	83,245
	November 2014 equity offering (3)		8,620,153			153,061			70.85			18,615		602,967
	$500.0 million COP (4)		480,109			—			65.55			396		31,076
	(1)	Represents general partner units issued to the general partner in exchange for the general partner’s proportionate capital contribution.
	(2)	Represents common and general partner units issued during the year ended December 31, 2014, pursuant to the Partnership’s registration statement filed with the SEC in August 2012 authorizing the issuance of up to an aggregate of $125.0 million of common units (the “$125.0 million COP”). Gross proceeds generated (including the general partner’s proportionate capital contributions) during the year ended December 31, 2014, were $85.0 million. The price per unit in the table above represents an average price for all issuances under the $125.0 million COP during the year ended December 31, 2014. As of December 31, 2014, the Partnership had used all the capacity to issue common units under this registration statement.
	(3)	Includes the issuance of 1,120,153 common units pursuant to the partial exercise of the underwriters’ over-allotment option, the net proceeds from which were $77.0 million. Beginning with this partial exercise, the Partnership’s general partner elected not to make a corresponding capital contribution to maintain its 2.0% interest in the Partnership.
	(4)	Represents common units issued during the three months ended March 31, 2015, pursuant to the Partnership’s registration statement filed with the SEC in August 2014 authorizing the issuance of up to an aggregate of $500.0 million of common units (the “$500.0 million COP”). Gross proceeds generated and commissions paid during the three months ended March 31, 2015, were $31.5 million and $0.3 million, respectively. The price per unit in the table above represents an average price for all issuances under the $500.0 million COP during the three months ended March 31, 2015. Does not include sales of 289,744 common units that settled after March 31, 2015.
	4.  EQUITY AND PARTNERS’ CAPITAL (CONTINUED)
	Class C units. In connection with the closing of the DBM acquisition in November 2014, the Partnership issued 10,913,853 Class C units to AMH at a price of $68.72 per unit, generating proceeds of $750.0 million, pursuant to the Unit Purchase Agreement (“UPA”) with Anadarko and AMH. All outstanding Class C units will convert into common units on a one-for-one basis on December 31, 2017, unless the Partnership elects to convert such units earlier or Anadarko extends the conversion date. The Class C units were issued to partially fund the acquisition of DBM, and the UPA contains an optional redemption feature that provides the Partnership the ability to redeem up to $150.0 million of the Class C units within 10 days of the receipt of cash proceeds from an entity that is not an affiliate of the Partnership or AMH, if these cash proceeds were in relation to (i) the assets of DBM, (ii) the equity interests in DBM or (iii) the equity interests in a subsidiary of the Partnership that owns a majority of the outstanding equity interests in DBM. As of March 31, 2015, no such proceeds had been received and no Class C units had been redeemed.
	The Class C units were issued at a discount to the then-current market price of the common units into which they are convertible. This discount, totaling $34.8 million, represents a beneficial conversion feature and at December 31, 2014, was reflected as an increase in common unitholders’ capital and a decrease in Class C unitholder capital to reflect the fair value of the Class C units at issuance. The beneficial conversion feature is considered a non-cash distribution that will be recognized from the date of issuance through the date of conversion, resulting in an increase in Class C unitholder capital and a decrease in common unitholders’ capital. The Partnership is amortizing the beneficial conversion feature assuming a conversion date of December 31, 2017, using the effective yield method. The impact of the beneficial conversion feature is also included in the calculation of earnings per unit.
	Common, Class C and general partner units. The Partnership’s common units are listed on the New York Stock Exchange under the symbol “WES.”
	The following table summarizes the common, Class C and general partner units issued during the three months ended March 31, 2015:
			Common			Class C Units			General		Total
			Units						Partner Units
	Balance at December 31, 2014		127,695,130			10,913,853			2,583,068		141,192,051
	PIK Class C units		—			45,711			—		45,711
	Long-Term Incentive Plan award vestings		2,014			—			—		2,014
	$500.0 million COP		480,109			—			—		480,109
	Balance at March 31, 2015		128,177,253			10,959,564			2,583,068		141,719,885
	Holdings of Partnership equity. As of March 31, 2015, WGP held 49,296,205 common units, representing a 34.8% limited partner interest in the Partnership, and, through its ownership of the general partner, WGP indirectly held 2,583,068 general partner units, representing a 1.8% general partner interest in the Partnership, and 100% of the Partnership’s IDRs. As of March 31, 2015, other subsidiaries of Anadarko held 757,619 common units and 10,959,564 Class C units, representing an aggregate 8.3% limited partner interest in the Partnership. As of March 31, 2015, the public held 78,123,429 common units, representing a 55.1% limited partner interest in the Partnership.
	Net income per unit for common units. The Partnership’s net income earned on and subsequent to the date of the acquisition of the Partnership assets is allocated to the general partner and the limited partners, including any Class C unitholders, in accordance with their respective weighted-average ownership percentages and, when applicable, giving effect to incentive distributions allocable to the general partner. The Partnership’s net income allocable to the limited partners is net of amortization of the beneficial conversion feature related to the Class C units (see Class C units above) and is allocated between the common and Class C unitholders by applying the provisions of the partnership agreement that govern actual cash distributions and capital account allocations, as if all earnings for the period had been distributed. Net income attributable to the Partnership assets acquired from Anadarko for periods prior to the Partnership’s acquisition of the Partnership assets is not allocated to the limited partners for purposes of calculating net income per common unit.
	4.  EQUITY AND PARTNERS’ CAPITAL (CONTINUED)
	Basic net income per common unit is calculated by dividing the limited partners’ interest in net income attributable to common unitholders by the weighted-average number of common units outstanding during the period. The common units issued in connection with acquisitions and equity offerings are included on a weighted-average basis for periods they were outstanding. Because the Class C units participate in distributions with common units according to a predetermined formula (see Note 3), they are considered a participating security and are included in the computation of earnings per unit pursuant to the two-class method. The Class C unit participation right results in a non-contingent transfer of value each time the Partnership declares a distribution. Diluted net income per common unit is calculated by dividing the sum of (i) the limited partners’ interest in net income attributable to common units, and (ii) the limited partners’ interest in net income allocable to the Class C units as a participating security, by the sum of the weighted-average number of common units outstanding plus the dilutive effect of outstanding Class C units.
	The following table illustrates the Partnership’s calculation of net income per unit for common units:
			Three Months Ended
			March 31,
	thousands except per-unit amounts		2015				2014
	Net income attributable to Western Gas Partners, LP		$	83,568			$	91,056
	Pre-acquisition net (income) loss allocated to Anadarko		(1,742		)		(2,665		)
	General partner interest in net (income) loss		(41,993		)		(24,834		)
	Limited partners’ interest in net income		39,833				63,557
	Net income allocable to common units (1)		32,891				63,557
	Net income allocable to Class C units (1)		6,942				—
	Limited partners’ interest in net income		$	39,833			$	63,557
	Net income per unit
	Common units - basic		$	0.26			$	0.54
	Common units – diluted (2)		0.26				0.54
	Weighted-average units outstanding
	Common units – basic		127,736				117,716
	Class C units		10,938				—
	Common units – diluted		138,674				117,716
	(1)	Adjusted to reflect amortization for the beneficial conversion feature. See Class C units above for a discussion of the Class C units.
	(2)	Inclusion of 10,938,232 Class C units in the calculation would have had an anti-dilutive effect.

Transactions_With_Affiliates

Transactions With Affiliates	3 Months Ended
	Mar. 31, 2015
Related Party Fees and Other Arrangements, Limited Liability Company (LLC) or Limited Partnership (LP) [Abstract]
Transactions with Affiliates	5.  TRANSACTIONS WITH AFFILIATES
	Affiliate transactions. Revenues from affiliates include amounts earned by the Partnership from services provided to Anadarko as well as from the sale of residue, drip condensate and NGLs to Anadarko. In addition, the Partnership purchases natural gas from an affiliate of Anadarko pursuant to gas purchase agreements. Operation and maintenance expense includes amounts accrued for or paid to affiliates for the operation of the Partnership assets, whether in providing services to affiliates or to third parties, including field labor, measurement and analysis, and other disbursements. A portion of the Partnership’s general and administrative expenses is paid by Anadarko, which results in affiliate transactions pursuant to the reimbursement provisions of the Partnership’s omnibus agreement. Affiliate expenses do not bear a direct relationship to affiliate revenues, and third-party expenses do not bear a direct relationship to third-party revenues. See Note 2 for further information related to contributions of assets to the Partnership by Anadarko.
	5.  TRANSACTIONS WITH AFFILIATES (CONTINUED)
	Cash management. Anadarko operates a cash management system whereby excess cash from most of its subsidiaries’ separate bank accounts is generally swept to centralized accounts. Prior to the Partnership’s acquisition of the Partnership assets, third-party sales and purchases related to such assets were received or paid in cash by Anadarko within its centralized cash management system. The outstanding affiliate balances were entirely settled through an adjustment to net investment by Anadarko in connection with the acquisition of the Partnership assets. Subsequent to the acquisition of Partnership assets from Anadarko, transactions related to such assets are cash-settled directly with third parties and with Anadarko affiliates. Chipeta cash settles its transactions directly with third parties and Anadarko, as well as with the other subsidiaries of the Partnership.
	Note receivable from and Deferred purchase price obligation - Anadarko. Concurrently with the closing of the Partnership’s May 2008 initial public offering, the Partnership loaned $260.0 million to Anadarko in exchange for a 30-year note bearing interest at a fixed annual rate of 6.50%, payable quarterly. The fair value of the note receivable from Anadarko was $327.0 million and $317.8 million at March 31, 2015, and December 31, 2014, respectively. The fair value of the note reflects consideration of credit risk and any premium or discount for the differential between the stated interest rate and quarter-end market interest rate, based on quoted market prices of similar debt instruments. Accordingly, the fair value of the note receivable from Anadarko is measured using Level 2 inputs.
	The consideration to be paid by the Partnership for the March 2015 acquisition of DBJV consists of a cash payment to Anadarko due on March 31, 2020. See Note 2 and Note 9.
	Commodity price swap agreements. The Partnership has commodity price swap agreements with Anadarko to mitigate exposure to a substantial majority of the commodity price volatility that would otherwise be present as a result of the purchase and sale of natural gas, condensate or NGLs. Notional volumes for each of the commodity price swap agreements are not specifically defined. Instead, the commodity price swap agreements apply to the actual volume of natural gas, condensate and NGLs purchased and sold at the Hugoton system, the MGR assets and the DJ Basin complex, with various expiration dates through December 2016. On December 31, 2014, the Partnership’s commodity price swap agreements for the Hilight and Newcastle systems and the Granger complex (excluding the Granger straddle plant) expired without renewal. The commodity price swap agreements do not satisfy the definition of a derivative financial instrument and, therefore, are not required to be measured at fair value.
	Below is a summary of the fixed price ranges on the Partnership’s outstanding commodity price swap agreements as of March 31, 2015:
	per barrel except natural gas		2015							2016
	Ethane		$	18.41		−	23.41			$	23.11
	Propane		47.08			−	52.99			52.9
	Isobutane		62.09			−	74.02			73.89
	Normal butane		54.62			−	65.04			64.93
	Natural gasoline		72.88			−	81.82			81.68
	Condensate		76.47			−	81.82			81.68
	Natural gas (per MMBtu)		4.66			−	5.96			4.87
	5.  TRANSACTIONS WITH AFFILIATES (CONTINUED)
	The following table summarizes realized gains and losses on commodity price swap agreements:
			Three Months Ended
			March 31,
	thousands		2015				2014
	Gains (losses) on commodity price swap agreements related to sales: (1)
	Natural gas sales		$	10,982			$	(3,667	)
	Natural gas liquids sales		44,432				9,455
	Total		55,414				5,788
	Losses on commodity price swap agreements related to purchases (2)		(34,179		)		(19		)
	Net gains (losses) on commodity price swap agreements		$	21,235			$	5,769
	(1)	Reported in affiliate natural gas, natural gas liquids and drip condensate sales in the consolidated statements of income in the period in which the related sale is recorded.
	(2)	Reported in cost of product in the consolidated statements of income in the period in which the related purchase is recorded.
	Gas gathering and processing agreements. The Partnership has significant gas gathering and processing arrangements with affiliates of Anadarko on a majority of its systems. The Partnership’s gathering, transportation and treating throughput (excluding equity investment throughput and throughput measured in barrels) attributable to natural gas production owned or controlled by Anadarko was 48% and 49% for the three months ended March 31, 2015 and 2014, respectively. The Partnership’s processing throughput (excluding equity investment throughput and throughput measured in barrels) attributable to natural gas production owned or controlled by Anadarko was 52% and 59% for the three months ended March 31, 2015 and 2014, respectively.
	Purchase and sale agreements. The Partnership sells a significant amount of its natural gas, condensate and NGLs to Anadarko Energy Services Company (“AESC”), Anadarko’s marketing affiliate. In addition, the Partnership purchases natural gas, condensate and NGLs from AESC pursuant to purchase agreements. The Partnership’s purchase and sale agreements with AESC are generally one-year contracts, subject to annual renewal.
	WES LTIP. The general partner awards phantom units under the Western Gas Partners, LP 2008 Long-Term Incentive Plan (“WES LTIP”) primarily to its independent directors, but also from time to time to its executive officers and Anadarko employees performing services for the Partnership. The phantom units awarded to the independent directors vest one year from the grant date, while all other awards are subject to graded vesting over a three-year service period. Compensation expense is recognized over the vesting period and was $0.1 million for each of the three months ended March 31, 2015 and 2014.
	WGP LTIP and Anadarko Incentive Plans. For the three months ended March 31, 2015 and 2014, general and administrative expenses included $1.0 million and $0.9 million, respectively, of equity-based compensation expense, allocated to the Partnership by Anadarko, for awards granted to the executive officers of the general partner and other employees under the Western Gas Equity Partners, LP 2012 Long-Term Incentive Plan (“WGP LTIP”), and the Anadarko Petroleum Corporation 1999 Stock Incentive Plan and the Anadarko Petroleum Corporation 2008 and 2012 Omnibus Incentive Compensation Plans (collectively referred to as the “Anadarko Incentive Plans”). Of this amount, $0.8 million is reflected as a contribution to partners’ capital in the Partnership’s consolidated statement of equity and partners’ capital for the three months ended March 31, 2015.
	5.  TRANSACTIONS WITH AFFILIATES (CONTINUED)
	Equipment purchases. The following table summarizes the Partnership’s purchases from Anadarko of pipe and equipment:
			Three Months Ended March 31,
			2015				2014
	thousands		Purchases
	Cash consideration		$	1,128			$	4,702
	Net carrying value		780				4,745
	Partners’ capital adjustment		$	348			$	(43	)
	Summary of affiliate transactions. The following table summarizes affiliate transactions, which include revenue from affiliates, reimbursement of operating expenses and purchases of natural gas:
			Three Months Ended
			March 31,
	thousands		2015				2014
	Revenues (1)		$	245,715			$	214,996
	Equity income, net (1)		18,220				9,251
	Cost of product (1)		42,407				18,356
	Operation and maintenance (2)		15,376				12,551
	General and administrative (3)		7,566				7,303
	Operating expenses		65,349				38,210
	Interest income (4)		4,225				4,225
	Interest expense (5)		1,420				—
	Distributions to unitholders (6)		71,695				51,882
	(1)	Represents amounts earned or incurred on and subsequent to the date of acquisition of the Partnership assets, as well as amounts earned or incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets, recognized under gathering, treating or processing agreements, and purchase and sale agreements.
	(2)	Represents expenses incurred on and subsequent to the date of the acquisition of the Partnership assets, as well as expenses incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets.
	(3)	Represents general and administrative expense incurred on and subsequent to the date of the Partnership’s acquisition of the Partnership assets, as well as a management services fee for reimbursement of expenses incurred by Anadarko for periods prior to the acquisition of the Partnership assets by the Partnership. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see WES LTIP and WGP LTIP and Anadarko Incentive Plans within this Note 5).
	(4)	Represents interest income recognized on the note receivable from Anadarko.
	(5)	For the three months ended March 31, 2015, includes accretion expense recognized on the Deferred purchase price obligation - Anadarko for the acquisition of DBJV (see Note 2 and Note 9).
	(6)	Represents distributions paid under the partnership agreement (see Note 3 and Note 4).
	Concentration of credit risk. Anadarko was the only customer from whom revenues exceeded 10% of the Partnership’s consolidated revenues for all periods presented in the consolidated statements of income.

Property_Plant_and_Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2015
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	6.  PROPERTY, PLANT AND EQUIPMENT
	A summary of the historical cost of the Partnership’s property, plant and equipment is as follows:
	thousands	Estimated Useful Life	31-Mar-15		December 31, 2014
	Land	n/a	$	3,260	$	2,884
	Gathering systems	3 to 47 years	5,232,882		4,972,892
	Pipelines and equipment	15 to 45 years	135,916		151,107
	Assets under construction	n/a	424,779		483,347
	Other	3 to 40 years	18,077		16,420
	Total property, plant and equipment		5,814,914		5,626,650
	Accumulated depreciation		1,103,643		1,055,207
	Net property, plant and equipment		$	4,711,271	$	4,571,443
	The cost of property classified as “Assets under construction” is excluded from capitalized costs being depreciated. These amounts represent property that is not yet suitable to be placed into productive service as of the respective balance sheet date.
	During 2015, the Partnership recognized impairments of $8.2 million, primarily due to the abandonment of compressors at the MIGC system and the DJ Basin complex.

Equity_Investments

Equity Investments	3 Months Ended
	Mar. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Equity Investments	7. EQUITY INVESTMENTS
	The following table presents the activity in the Partnership’s equity investments for the three months ended March 31, 2015:
		Equity Investments
	thousands	Fort			White			Rendezvous			Mont			TEG			TEP			FRP			Total
		Union			Cliffs						Belvieu JV
	Balance at December 31, 2014	$	25,933		$	44,315		$	56,336		$	121,337		$	16,790		$	198,793		$	170,988		$	634,492
	Investment earnings (loss), net of amortization	1,555			3,980			377			5,791			190			3,616			2,711			18,220
	Contributions	—			2,917			—			(432		)	—			1,180			1,213			4,878
	Distributions	(948		)	(3,834		)	(862		)	(6,291		)	(337		)	(3,679		)	(2,755		)	(18,706		)
	Distributions in excess of cumulative earnings (1)	—			(902		)	(736		)	—			—			(581		)	(745		)	(2,964		)
	Balance at March 31, 2015	$	26,540		$	46,476		$	55,115		$	120,405		$	16,643		$	199,329		$	171,412		$	635,920
	(1)	Distributions in excess of cumulative earnings, classified as investing cash flows in the consolidated statements of cash flows, is calculated on an individual investment basis.

Components_of_Working_Capital

Components of Working Capital	3 Months Ended
	Mar. 31, 2015
Components Of Working Capital [Abstract]
Components of Working Capital	8.  COMPONENTS OF WORKING CAPITAL
	A summary of other current assets is as follows:
	thousands		31-Mar-15		31-Dec-14
	Natural gas liquids inventory		$	6,087	$	5,316
	Natural gas imbalance receivables		1,682		415
	Prepaid insurance		1,416		2,443
	Other		1,295		1,893
	Total other current assets		$	10,480	$	10,067
	A summary of accrued liabilities is as follows:
	thousands		31-Mar-15		31-Dec-14
	Accrued capital expenditures		$	94,176	$	128,856
	Accrued plant purchases		37,826		14,023
	Accrued interest expense		27,995		24,741
	Short-term asset retirement obligations		5,739		1,224
	Short-term remediation and reclamation obligations		475		475
	Income taxes payable		299		207
	Other (1)		5,099		1,263
	Total accrued liabilities		$	171,609	$	170,789
	(1)	Includes $3.5 million of post-closing purchase price adjustments at March 31, 2015, related to the acquisition of DBM.

Debt_and_Interest_Expense

Debt and Interest Expense	3 Months Ended
	Mar. 31, 2015
Debt Instruments [Abstract]
Debt and Interest Expense	9.  DEBT AND INTEREST EXPENSE
	At March 31, 2015, the Partnership’s debt consisted of 5.375% Senior Notes due 2021 (the “2021 Notes”), 4.000% Senior Notes due 2022 (the “2022 Notes”), 2.600% Senior Notes due 2018 (the “2018 Notes”), 5.450% Senior Notes due 2044 (the “2044 Notes”), and borrowings on the senior unsecured revolving credit facility (“RCF”).
	The following table presents the Partnership’s outstanding debt as of March 31, 2015, and December 31, 2014:
			31-Mar-15								31-Dec-14
	thousands		Principal			Carrying			Fair		Principal		Carrying		Fair
						Value			Value (1)				Value		Value (1)
	2021 Notes		$	500,000		$	495,854		$	555,175	$	500,000	$	495,714	$	549,530
	2022 Notes		670,000			672,841			683,554		670,000		672,930		681,942
	RCF		620,000			620,000			620,000		510,000		510,000		510,000
	2018 Notes		350,000			350,443			355,372		350,000		350,474		352,162
	2044 Notes		400,000			393,857			433,456		400,000		393,836		417,619
	Total long-term debt		$	2,540,000		$	2,532,995		$	2,647,557	$	2,430,000	$	2,422,954	$	2,511,253
	(1)	Fair value is measured using Level 2 inputs.
	9.  DEBT AND INTEREST EXPENSE (CONTINUED)
	Debt activity. The following table presents the debt activity of the Partnership for the three months ended March 31, 2015:
	thousands		Carrying Value
	Balance at December 31, 2014		$	2,422,954
	RCF borrowings		140,000
	Repayment of RCF		(30,000		)
	Other		41
	Balance at March 31, 2015		$	2,532,995
	Senior Notes. At March 31, 2015, the Partnership was in compliance with all covenants under the indentures governing the 2021 Notes, 2022 Notes, 2018 Notes and 2044 Notes.
	Revolving credit facility. The interest rate on the RCF, which matures in February 2019, was 1.48% and 1.47% at March 31, 2015, and December 31, 2014, respectively. The facility fee rate was 0.20% at March 31, 2015, and December 31, 2014.
	As of March 31, 2015, the Partnership had $620.0 million of outstanding borrowings, $12.8 million in outstanding letters of credit and $567.2 million available for borrowing under the RCF. At March 31, 2015, the Partnership was in compliance with all covenants under the RCF.
	Interest expense. The following table summarizes the amounts included in interest expense:
			Three Months Ended
			March 31,
	thousands		2015			2014
	Third parties
	Long-term debt		$	23,342		$	16,135
	Amortization of debt issuance costs and commitment fees		1,292			1,266
	Capitalized interest		(3,094		)	(3,440		)
	Total interest expense – third parties		21,540			13,961
	Affiliates
	Deferred purchase price obligation – Anadarko (1)		1,420			—
	Total interest expense – affiliates		1,420			—
	Interest expense		$	22,960		$	13,961
	(1)	See Note 2 for a discussion of the accretion and present value of the Deferred purchase price obligation - Anadarko.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	10.  COMMITMENTS AND CONTINGENCIES
	Litigation and legal proceedings. In March 2011, DCP Midstream, LP (“DCP”) filed a lawsuit against Anadarko and others, including a Partnership subsidiary, Kerr-McGee Gathering, LLC, in Weld County District Court (the “Court”) in Colorado, alleging that Anadarko diverted gas from DCP’s gathering and processing facilities in breach of certain dedication agreements. In addition to various claims against Anadarko, DCP is claiming unjust enrichment and other damages against Kerr-McGee Gathering, LLC, the entity that holds the Wattenberg assets (located in the DJ Basin complex). Anadarko countersued DCP asserting that DCP has not properly allocated values and charges to Anadarko for the gas that DCP gathers and/or processes, and seeks a judgment that DCP has no valid gathering or processing rights to much of the gas production it is claiming, in addition to other claims.
	The Court has scheduled this matter for trial in June 2016, and the parties are currently engaged in discovery and motion practice. Management does not believe the outcome of this proceeding will have a material effect on the Partnership’s financial condition, results of operations or cash flows. The Partnership intends to vigorously defend this litigation. Furthermore, without regard to the merit of DCP’s claims, management believes that the Partnership has adequate contractual indemnities covering the claims against it in this lawsuit.
	In addition, from time to time, the Partnership is involved in legal, tax, regulatory and other proceedings in various forums regarding performance, contracts and other matters that arise in the ordinary course of business. Management is not aware of any such proceeding for which a final disposition could have a material adverse effect on the Partnership’s financial condition, results of operations or cash flows.
	Other commitments. The Partnership has short-term payment obligations, or commitments, related to its capital spending programs, as well as those of its unconsolidated affiliates. As of March 31, 2015, the Partnership had unconditional payment obligations for services to be rendered or products to be delivered in connection with its capital projects of $24.1 million, the majority of which is expected to be paid in the next twelve months. These commitments relate primarily to projects at the DJ Basin complex, which include the continued construction of Train II at the Lancaster plant and compressor expansions, as well as projects at the Hilight system and the Red Desert complex.
	Lease commitments. Anadarko, on behalf of the Partnership, has entered into lease agreements for corporate offices, shared field offices and a warehouse supporting the Partnership’s operations, for which Anadarko charges the Partnership rent. The leases for the corporate offices and shared field offices extend through 2017 and 2018, respectively, and the lease for the warehouse extends through February 2017.
	Rent expense associated with the office, warehouse and equipment leases was $4.2 million and $2.3 million for the three months ended March 31, 2015 and 2014, respectively.

Description_of_Business_and_Ba1

Description of Business and Basis of Presentation (policies)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Business combinations policy	Basis of presentation. The consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”). The consolidated financial statements include the accounts of the Partnership and entities in which it holds a controlling financial interest. All significant intercompany transactions have been eliminated. Investments in non-controlled entities over which the Partnership exercises significant influence are accounted for under the equity method. The Partnership proportionately consolidates its 33.75% share of the assets, liabilities, revenues and expenses attributable to the Non-Operated Marcellus Interest systems and Anadarko-Operated Marcellus Interest systems and its 50% share of the assets, liabilities, revenues and expenses attributable to the Newcastle system and the DBJV system (see Note 2) in the accompanying consolidated financial statements.
	In preparing financial statements in accordance with GAAP, management makes informed judgments and estimates that affect the reported amounts of assets, liabilities, revenues and expenses. Management evaluates its estimates and related assumptions regularly, using historical experience and other methods considered reasonable. Changes in facts and circumstances or additional information may result in revised estimates and actual results may differ from these estimates. Effects on the business, financial condition and results of operations resulting from revisions to estimates are recognized when the facts that give rise to the revisions become known. The information furnished herein reflects all normal recurring adjustments which are, in the opinion of management, necessary for a fair presentation of the consolidated financial statements, and certain prior-period amounts have been reclassified to conform to the current-year presentation.
	Presentation of Partnership assets. The term “Partnership assets” refers to the assets owned and interests accounted for under the equity method (see Note 7) by the Partnership as of March 31, 2015. Because Anadarko controls the Partnership through its ownership and control of WGP, which owns the Partnership’s entire general partner interest, each acquisition of Partnership assets from Anadarko has been considered a transfer of net assets between entities under common control. As such, the Partnership assets acquired from Anadarko were initially recorded at Anadarko’s historic carrying value, which did not correlate to the total acquisition price paid by the Partnership. Further, after an acquisition of Partnership assets from Anadarko, the Partnership may be required to recast its financial statements to include the activities of such Partnership assets from the date of common control. See Note 2.
	For those periods requiring recast, the consolidated financial statements for periods prior to the Partnership’s acquisition of the Partnership assets from Anadarko have been prepared from Anadarko’s historical cost-basis accounts and may not necessarily be indicative of the actual results of operations that would have occurred if the Partnership had owned the Partnership assets during the periods reported. Net income attributable to the Partnership assets acquired from Anadarko for periods prior to the Partnership’s acquisition of the Partnership assets is not allocated to the limited partners.
	DBM acquisition. The DBM acquisition has been accounted for under the acquisition method of accounting. The assets acquired and liabilities assumed in the DBM acquisition were recorded in the consolidated balance sheet at their estimated fair values as of the acquisition date. Results of operations attributable to the DBM acquisition were included in the Partnership’s consolidated statement of income beginning on the acquisition date in the fourth quarter of 2014.
Net income per common unit policy	Net income per unit for common units. The Partnership’s net income earned on and subsequent to the date of the acquisition of the Partnership assets is allocated to the general partner and the limited partners, including any Class C unitholders, in accordance with their respective weighted-average ownership percentages and, when applicable, giving effect to incentive distributions allocable to the general partner. The Partnership’s net income allocable to the limited partners is net of amortization of the beneficial conversion feature related to the Class C units (see Class C units above) and is allocated between the common and Class C unitholders by applying the provisions of the partnership agreement that govern actual cash distributions and capital account allocations, as if all earnings for the period had been distributed. Net income attributable to the Partnership assets acquired from Anadarko for periods prior to the Partnership’s acquisition of the Partnership assets is not allocated to the limited partners for purposes of calculating net income per common unit.
	Basic net income per common unit is calculated by dividing the limited partners’ interest in net income attributable to common unitholders by the weighted-average number of common units outstanding during the period. The common units issued in connection with acquisitions and equity offerings are included on a weighted-average basis for periods they were outstanding. Because the Class C units participate in distributions with common units according to a predetermined formula (see Note 3), they are considered a participating security and are included in the computation of earnings per unit pursuant to the two-class method. The Class C unit participation right results in a non-contingent transfer of value each time the Partnership declares a distribution. Diluted net income per common unit is calculated by dividing the sum of (i) the limited partners’ interest in net income attributable to common units, and (ii) the limited partners’ interest in net income allocable to the Class C units as a participating security, by the sum of the weighted-average number of common units outstanding plus the dilutive effect of outstanding Class C units.
Fair value policy	Deferred purchase price obligation - Anadarko. The consideration to be paid by the Partnership for the acquisition of DBJV consists of a cash payment to Anadarko due on March 31, 2020. The cash payment will be equal to eight multiplied by (a) the average of the Partnership’s share in the Net Earnings (see definition below) of the DBJV system for the calendar years 2018 and 2019, less (b) the Partnership’s share of all capital expenditures incurred for the DBJV system between March 1, 2015, and February 29, 2020. Net Earnings is defined as all revenues less cost of product, operating expenses and property taxes, in each case attributable to the DBJV system on an accrual basis. As of the acquisition date, the estimated future payment obligation was $282.8 million, which had a net present value of $174.3 million, using a discount rate of 10%. As of March 31, 2015, the net present value of this obligation was $175.7 million and has been recorded on the consolidated balance sheet under Deferred purchase price obligation - Anadarko. Accretion expense for the three months ended March 31, 2015, was $1.4 million and has been recorded as a charge to interest expense. The fair value measurement was calculated using Level 3 inputs, which consisted of management’s estimate of the Partnership’s share of forecasted Net Earnings and capital expenditures for the DBJV system.
	DBM acquisition. The DBM acquisition has been accounted for under the acquisition method of accounting. The assets acquired and liabilities assumed in the DBM acquisition were recorded in the consolidated balance sheet at their estimated fair values as of the acquisition date. Results of operations attributable to the DBM acquisition were included in the Partnership’s consolidated statement of income beginning on the acquisition date in the fourth quarter of 2014.
	The purchase price allocation is based on an assessment of the fair value of the assets acquired and liabilities assumed in the DBM acquisition using inputs that are not observable in the market and thus represent Level 3 inputs. The fair values of the processing plants, gathering system, and related facilities and equipment are based on market and cost approaches. The fair value of the intangible assets was determined using an income approach. Deferred taxes represent the tax effects of differences in the tax basis and acquisition-date fair value of the assets acquired and liabilities assumed.
	Class C unit distributions. The Class C units receive quarterly distributions at a rate equivalent to the Partnership’s common units. The distributions are paid in the form of additional Class C units (“PIK Class C units”) until the end of 2017 (unless earlier converted), and the Class C units are disregarded with respect to distributions of the Partnership’s available cash until they are converted to common units. The number of additional PIK Class C units to be issued in connection with a distribution payable on the Class C units is determined by dividing the corresponding distribution attributable to the Class C units by the volume-weighted-average price of the Partnership’s common units for the ten days immediately preceding the payment date for the common unit distribution, less a 6% discount. The Partnership records the PIK Class C unit distributions at fair value at the time of issuance. This Level 2 fair value measurement uses the Partnership’s unit price as a significant input in the determination of the fair value. On February 12, 2015, the Partnership issued 45,711 PIK Class C units to APC Midstream Holdings, LLC (“AMH”), a subsidiary of Anadarko and the holder of the Class C units, based on the $0.700 common unit distribution for the fourth quarter of 2014, with an implied fair value of $3.1 million. The Class C unit distribution was prorated for the 37-day period the Class C units were outstanding during the fourth quarter of 2014.
	Note receivable from and Deferred purchase price obligation - Anadarko. Concurrently with the closing of the Partnership’s May 2008 initial public offering, the Partnership loaned $260.0 million to Anadarko in exchange for a 30-year note bearing interest at a fixed annual rate of 6.50%, payable quarterly. The fair value of the note receivable from Anadarko was $327.0 million and $317.8 million at March 31, 2015, and December 31, 2014, respectively. The fair value of the note reflects consideration of credit risk and any premium or discount for the differential between the stated interest rate and quarter-end market interest rate, based on quoted market prices of similar debt instruments. Accordingly, the fair value of the note receivable from Anadarko is measured using Level 2 inputs.
Use of estimates policy	In preparing financial statements in accordance with GAAP, management makes informed judgments and estimates that affect the reported amounts of assets, liabilities, revenues and expenses. Management evaluates its estimates and related assumptions regularly, using historical experience and other methods considered reasonable. Changes in facts and circumstances or additional information may result in revised estimates and actual results may differ from these estimates. Effects on the business, financial condition and results of operations resulting from revisions to estimates are recognized when the facts that give rise to the revisions become known. The information furnished herein reflects all normal recurring adjustments which are, in the opinion of management, necessary for a fair presentation of the consolidated financial statements, and certain prior-period amounts have been reclassified to conform to the current-year presentation.
Recently issued accounting standards policy	Recently issued accounting standards. The Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2015-06, Earnings Per Share (Topic - 260)—Effects on Historical Earnings per Unit of Master Limited Partnership Dropdown Transactions. This ASU contains guidance that addresses the historical earnings per unit presentation for master limited partnerships that apply the two-class method of calculating earnings per unit. When a general partner transfers or “drops down” net assets to a master limited partnership the transactions is accounted for as a transaction between entities under common control and the statements of operations are adjusted retrospectively to reflect the transaction. This ASU specifies that the historical earnings (losses) of a transferred business before the date of a dropdown transaction should be allocated entirely to the general partner, and the previously reported earnings per unit of the limited partners should not change as a result of the dropdown transaction. The ASU also requires additional 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. This ASU is effective for annual and interim periods beginning in 2016 and is required to be adopted using a retrospective approach, with early adoption permitted. The Partnership believes it is currently in compliance with this ASU, but will continue to evaluate the impact of the adoption of this ASU on its consolidated financial statements.
	The FASB issued ASU 2015-03, Interest—Imputation of Interest (Subtopic 853-30)—Simplifying the Presentation of Debt Issuance Costs. This ASU will simplify the presentation of debt issuance costs by requiring such costs to be presented in the balance sheet as a reduction from the corresponding debt liability rather than as an asset. This ASU is effective for annual and interim periods beginning in 2016 and is required to be adopted using a retrospective approach, with early adoption permitted. The Partnership is considering the alternatives for timing of adoption.
	The FASB issued ASU 2015-02, Consolidation—Amendments to the Consolidation Analysis. This ASU will simplify existing requirements by reducing the number of consolidation models and placing more emphasis on risk of loss when determining a controlling financial interest. The provisions will affect how limited partnerships and similar entities are assessed for consolidation, including the elimination of the presumption that a general partner should consolidate a limited partnership. This ASU is effective for annual and interim periods beginning in 2016 and is required to be adopted using a retrospective or modified retrospective approach, with early adoption permitted. The Partnership is evaluating the impact of the adoption of this ASU on its consolidated financial statements.
	The FASB issued ASU 2014-09, Revenue from Contracts with Customers. This ASU supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and industry-specific guidance in Subtopic 932-605, Extractive Activities—Oil and Gas—Revenue Recognition, and requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration the entity expects to be entitled to in exchange for those goods or services. This ASU is effective for annual and interim periods beginning in 2017 and is required to be adopted using one of two retrospective application methods, with no early adoption permitted. The Partnership is evaluating the impact of the adoption of this ASU on its consolidated financial statements.

Description_of_Business_and_Ba2

Description of Business and Basis of Presentation (tables)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Assets and Investments Table	As of March 31, 2015, the Partnership’s assets and investments accounted for under the equity method consisted of the following:
		Owned and	Operated	Non-Operated	Equity Interests
		Operated	Interests	Interests
	Natural gas gathering systems	14	2	5	2
	Natural gas treating facilities	8	5	—	1
	Natural gas processing facilities	13	3	—	2
	NGL pipelines	3	—	—	3
	Natural gas pipelines	4	—	—	—
	Oil pipelines	1	—	—	1

Acquisitions_tables

Acquisitions (tables)	3 Months Ended
	Mar. 31, 2015
Business Combinations [Abstract]
Acquisitions Table	The following table presents the acquisitions completed by the Partnership during 2015 and 2014, and identifies the funding sources for such acquisitions:
	thousands except unit and percent amounts		Acquisition		Percentage			Deferred Purchase Price Obligation - Anadarko			Borrowings		Cash		Common	Class C Units Issued to Anadarko
			Date		Acquired								On Hand		Units Issued to Anadarko
	TEFR Interests (1)		3/3/14		Various (1)			$	—		$	350,000	$	6,250	308,490	—
	DBM (2)		11/25/14		100	%		—			475,000		298,327		—	10,913,853
	DBJV system (3)		3/2/15		50	%		174,276			—		—		—	—
	(1)	The Partnership acquired a 20% interest in each of TEG and TEP and a 33.33% interest in FRP from Anadarko. These assets gather and transport NGLs primarily from the Anadarko and Denver-Julesburg (“DJ”) Basins. The interests in these entities are accounted for under the equity method of accounting. In connection with the issuance of the common units, the Partnership’s general partner purchased 6,296 general partner units in exchange for the general partner’s proportionate capital contribution of $0.4 million.
	(2)	The Partnership acquired Nuevo Midstream, LLC (“Nuevo”) from a third party. Following the acquisition, the Partnership changed the name of Nuevo to Delaware Basin Midstream, LLC (“DBM”). The assets acquired include cryogenic processing plants, a gas gathering system, and related facilities and equipment, which are collectively referred to as the “DBM complex” and serve production from Reeves, Loving and Culberson Counties, Texas and Eddy and Lea Counties, New Mexico.
	(3)	The Partnership acquired Anadarko’s interest in Delaware Basin JV Gathering LLC (“DBJV”), which owns a 50% interest in a gathering system and related facilities (the “DBJV system”). The DBJV system is located in the Delaware Basin in Loving, Ward, Winkler and Reeves Counties, Texas. The Partnership will make a cash payment on March 31, 2020, to Anadarko as consideration for the acquisition of DBJV. The Partnership currently estimates the future payment will be $282.8 million, the net present value of which was $174.3 million as of the acquisition date. See Deferred purchase price obligation - Anadarko below.
Impact to Historical Consolidated Statement of Income Table	The following table presents the impact of the DBJV system on revenue, equity income, net and net income as presented in the Partnership’s historical consolidated statements of income:
			Three Months Ended March 31, 2014
	thousands		Partnership Historical				DBJV System			Combined
	Revenues		$	279,457			$	14,260		$	293,717
	Equity income, net		9,251				—			9,251
	Net income		91,127				3,621			94,748
Purchase Price Allocation Table	The following is the preliminary allocation of the purchase price as of March 31, 2015, including $3.5 million of post-closing purchase price adjustments, to the assets acquired and liabilities assumed in the DBM acquisition as of the acquisition date, pending final review of support related to the acquired entity’s assets:
	thousands
	Current assets		$	63,020
	Property, plant and equipment		467,171
	Goodwill		282,999
	Other intangible assets		811,048
	Accounts payables		(17,679		)
	Accrued liabilities		(38,684		)
	Deferred income taxes		(1,342		)
	Asset retirement obligations and other		(9,060		)
	Total purchase price		$	1,557,473

Partnership_Distributions_tabl

Partnership Distributions (tables)	3 Months Ended
	Mar. 31, 2015
Distributions Made to Members or Limited Partners [Abstract]
Cash Distributions Table	The Board of Directors of the general partner declared the following cash distributions to the Partnership’s common and general partner unitholders for the periods presented:
	thousands except per-unit amounts		Total Quarterly		Total Quarterly		Date of
	Quarters Ended		Distribution		Cash Distribution		Distribution
			per Unit
	31-Mar-14		$	0.625	$	98,749	May 2014
	March 31, 2015 (1)		0.725		133,203		May 2015
	(1)	On April 20, 2015, the Board of Directors of the Partnership’s general partner declared a cash distribution to the Partnership’s unitholders of $0.725 per unit, or $133.2 million in aggregate, including incentive distributions, but excluding distributions on Class C units (see Class C unit distributions below). The cash distribution is payable on May 13, 2015, to unitholders of record at the close of business on April 30, 2015.

Equity_and_Partners_Capital_ta

Equity and Partners' Capital (tables)	3 Months Ended
	Mar. 31, 2015
Partners' Capital Notes [Abstract]
Equity Offerings Table	The Partnership completed the following public offerings of its common units during 2015 and 2014, including through its Continuous Offering Programs (“COP”):
	thousands except unit and per-unit amounts		Common Units Issued			GP Units Issued (1)			Price Per			Underwriting		Net
									Unit			Discount and		Proceeds
												Other Offering
												Expenses
	$125.0 million COP (2)		1,133,384			23,132			$	73.48		$	1,738	$	83,245
	November 2014 equity offering (3)		8,620,153			153,061			70.85			18,615		602,967
	$500.0 million COP (4)		480,109			—			65.55			396		31,076
	(1)	Represents general partner units issued to the general partner in exchange for the general partner’s proportionate capital contribution.
	(2)	Represents common and general partner units issued during the year ended December 31, 2014, pursuant to the Partnership’s registration statement filed with the SEC in August 2012 authorizing the issuance of up to an aggregate of $125.0 million of common units (the “$125.0 million COP”). Gross proceeds generated (including the general partner’s proportionate capital contributions) during the year ended December 31, 2014, were $85.0 million. The price per unit in the table above represents an average price for all issuances under the $125.0 million COP during the year ended December 31, 2014. As of December 31, 2014, the Partnership had used all the capacity to issue common units under this registration statement.
	(3)	Includes the issuance of 1,120,153 common units pursuant to the partial exercise of the underwriters’ over-allotment option, the net proceeds from which were $77.0 million. Beginning with this partial exercise, the Partnership’s general partner elected not to make a corresponding capital contribution to maintain its 2.0% interest in the Partnership.
	(4)	Represents common units issued during the three months ended March 31, 2015, pursuant to the Partnership’s registration statement filed with the SEC in August 2014 authorizing the issuance of up to an aggregate of $500.0 million of common units (the “$500.0 million COP”). Gross proceeds generated and commissions paid during the three months ended March 31, 2015, were $31.5 million and $0.3 million, respectively. The price per unit in the table above represents an average price for all issuances under the $500.0 million COP during the three months ended March 31, 2015. Does not include sales of 289,744 common units that settled after March 31, 2015.
Limited Partner and General Partner Units Table	The following table summarizes the common, Class C and general partner units issued during the three months ended March 31, 2015:
			Common			Class C Units			General		Total
			Units						Partner Units
	Balance at December 31, 2014		127,695,130			10,913,853			2,583,068		141,192,051
	PIK Class C units		—			45,711			—		45,711
	Long-Term Incentive Plan award vestings		2,014			—			—		2,014
	$500.0 million COP		480,109			—			—		480,109
	Balance at March 31, 2015		128,177,253			10,959,564			2,583,068		141,719,885
Calculation of Net Income Per Unit Table	The following table illustrates the Partnership’s calculation of net income per unit for common units:
			Three Months Ended
			March 31,
	thousands except per-unit amounts		2015				2014
	Net income attributable to Western Gas Partners, LP		$	83,568			$	91,056
	Pre-acquisition net (income) loss allocated to Anadarko		(1,742		)		(2,665		)
	General partner interest in net (income) loss		(41,993		)		(24,834		)
	Limited partners’ interest in net income		39,833				63,557
	Net income allocable to common units (1)		32,891				63,557
	Net income allocable to Class C units (1)		6,942				—
	Limited partners’ interest in net income		$	39,833			$	63,557
	Net income per unit
	Common units - basic		$	0.26			$	0.54
	Common units – diluted (2)		0.26				0.54
	Weighted-average units outstanding
	Common units – basic		127,736				117,716
	Class C units		10,938				—
	Common units – diluted		138,674				117,716
	(1)	Adjusted to reflect amortization for the beneficial conversion feature. See Class C units above for a discussion of the Class C units.
	(2)	Inclusion of 10,938,232 Class C units in the calculation would have had an anti-dilutive effect.

Transactions_With_Affiliates_t

Transactions With Affiliates (tables)	3 Months Ended
	Mar. 31, 2015
Related Party Fees and Other Arrangements, Limited Liability Company (LLC) or Limited Partnership (LP) [Abstract]
Commodity Price Swap Agreements Table	Below is a summary of the fixed price ranges on the Partnership’s outstanding commodity price swap agreements as of March 31, 2015:
	per barrel except natural gas		2015							2016
	Ethane		$	18.41		−	23.41			$	23.11
	Propane		47.08			−	52.99			52.9
	Isobutane		62.09			−	74.02			73.89
	Normal butane		54.62			−	65.04			64.93
	Natural gasoline		72.88			−	81.82			81.68
	Condensate		76.47			−	81.82			81.68
	Natural gas (per MMBtu)		4.66			−	5.96			4.87
Gains (Losses) on Commodity Price Swap Agreements Table	The following table summarizes realized gains and losses on commodity price swap agreements:
			Three Months Ended
			March 31,
	thousands		2015				2014
	Gains (losses) on commodity price swap agreements related to sales: (1)
	Natural gas sales		$	10,982			$	(3,667	)
	Natural gas liquids sales		44,432				9,455
	Total		55,414				5,788
	Losses on commodity price swap agreements related to purchases (2)		(34,179		)		(19		)
	Net gains (losses) on commodity price swap agreements		$	21,235			$	5,769
	(1)	Reported in affiliate natural gas, natural gas liquids and drip condensate sales in the consolidated statements of income in the period in which the related sale is recorded.
	(2)	Reported in cost of product in the consolidated statements of income in the period in which the related purchase is recorded.
Related Party Transactions Tables	The following table summarizes the Partnership’s purchases from Anadarko of pipe and equipment:
			Three Months Ended March 31,
			2015				2014
	thousands		Purchases
	Cash consideration		$	1,128			$	4,702
	Net carrying value		780				4,745
	Partners’ capital adjustment		$	348			$	(43	)
	The following table summarizes affiliate transactions, which include revenue from affiliates, reimbursement of operating expenses and purchases of natural gas:
			Three Months Ended
			March 31,
	thousands		2015				2014
	Revenues (1)		$	245,715			$	214,996
	Equity income, net (1)		18,220				9,251
	Cost of product (1)		42,407				18,356
	Operation and maintenance (2)		15,376				12,551
	General and administrative (3)		7,566				7,303
	Operating expenses		65,349				38,210
	Interest income (4)		4,225				4,225
	Interest expense (5)		1,420				—
	Distributions to unitholders (6)		71,695				51,882
	(1)	Represents amounts earned or incurred on and subsequent to the date of acquisition of the Partnership assets, as well as amounts earned or incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets, recognized under gathering, treating or processing agreements, and purchase and sale agreements.
	(2)	Represents expenses incurred on and subsequent to the date of the acquisition of the Partnership assets, as well as expenses incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets.
	(3)	Represents general and administrative expense incurred on and subsequent to the date of the Partnership’s acquisition of the Partnership assets, as well as a management services fee for reimbursement of expenses incurred by Anadarko for periods prior to the acquisition of the Partnership assets by the Partnership. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see WES LTIP and WGP LTIP and Anadarko Incentive Plans within this Note 5).
	(4)	Represents interest income recognized on the note receivable from Anadarko.
	(5)	For the three months ended March 31, 2015, includes accretion expense recognized on the Deferred purchase price obligation - Anadarko for the acquisition of DBJV (see Note 2 and Note 9).
	(6)	Represents distributions paid under the partnership agreement (see Note 3 and Note 4).

Property_Plant_and_Equipment_t

Property, Plant and Equipment (tables)	3 Months Ended
	Mar. 31, 2015
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment Table	A summary of the historical cost of the Partnership’s property, plant and equipment is as follows:
	thousands	Estimated Useful Life	31-Mar-15		December 31, 2014
	Land	n/a	$	3,260	$	2,884
	Gathering systems	3 to 47 years	5,232,882		4,972,892
	Pipelines and equipment	15 to 45 years	135,916		151,107
	Assets under construction	n/a	424,779		483,347
	Other	3 to 40 years	18,077		16,420
	Total property, plant and equipment		5,814,914		5,626,650
	Accumulated depreciation		1,103,643		1,055,207
	Net property, plant and equipment		$	4,711,271	$	4,571,443

Equity_Investments_tables

Equity Investments (tables)	3 Months Ended
	Mar. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Equity Investments Table	The following table presents the activity in the Partnership’s equity investments for the three months ended March 31, 2015:
		Equity Investments
	thousands	Fort			White			Rendezvous			Mont			TEG			TEP			FRP			Total
		Union			Cliffs						Belvieu JV
	Balance at December 31, 2014	$	25,933		$	44,315		$	56,336		$	121,337		$	16,790		$	198,793		$	170,988		$	634,492
	Investment earnings (loss), net of amortization	1,555			3,980			377			5,791			190			3,616			2,711			18,220
	Contributions	—			2,917			—			(432		)	—			1,180			1,213			4,878
	Distributions	(948		)	(3,834		)	(862		)	(6,291		)	(337		)	(3,679		)	(2,755		)	(18,706		)
	Distributions in excess of cumulative earnings (1)	—			(902		)	(736		)	—			—			(581		)	(745		)	(2,964		)
	Balance at March 31, 2015	$	26,540		$	46,476		$	55,115		$	120,405		$	16,643		$	199,329		$	171,412		$	635,920
	(1)	Distributions in excess of cumulative earnings, classified as investing cash flows in the consolidated statements of cash flows, is calculated on an individual investment basis.

Components_of_Working_Capital_

Components of Working Capital (tables)	3 Months Ended
	Mar. 31, 2015
Components Of Working Capital [Abstract]
Other Current Assets Table	A summary of other current assets is as follows:
	thousands		31-Mar-15		31-Dec-14
	Natural gas liquids inventory		$	6,087	$	5,316
	Natural gas imbalance receivables		1,682		415
	Prepaid insurance		1,416		2,443
	Other		1,295		1,893
	Total other current assets		$	10,480	$	10,067
Accrued Liabilities Table	A summary of accrued liabilities is as follows:
	thousands		31-Mar-15		31-Dec-14
	Accrued capital expenditures		$	94,176	$	128,856
	Accrued plant purchases		37,826		14,023
	Accrued interest expense		27,995		24,741
	Short-term asset retirement obligations		5,739		1,224
	Short-term remediation and reclamation obligations		475		475
	Income taxes payable		299		207
	Other (1)		5,099		1,263
	Total accrued liabilities		$	171,609	$	170,789
	(1)	Includes $3.5 million of post-closing purchase price adjustments at March 31, 2015, related to the acquisition of DBM.

Debt_and_Interest_Expense_tabl

Debt and Interest Expense (tables)	3 Months Ended
	Mar. 31, 2015
Debt Instruments [Abstract]
Debt Outstanding and Debt Activity Tables	The following table presents the Partnership’s outstanding debt as of March 31, 2015, and December 31, 2014:
			31-Mar-15								31-Dec-14
	thousands		Principal			Carrying			Fair		Principal		Carrying		Fair
						Value			Value (1)				Value		Value (1)
	2021 Notes		$	500,000		$	495,854		$	555,175	$	500,000	$	495,714	$	549,530
	2022 Notes		670,000			672,841			683,554		670,000		672,930		681,942
	RCF		620,000			620,000			620,000		510,000		510,000		510,000
	2018 Notes		350,000			350,443			355,372		350,000		350,474		352,162
	2044 Notes		400,000			393,857			433,456		400,000		393,836		417,619
	Total long-term debt		$	2,540,000		$	2,532,995		$	2,647,557	$	2,430,000	$	2,422,954	$	2,511,253
	(1)	Fair value is measured using Level 2 inputs.
	9.  DEBT AND INTEREST EXPENSE (CONTINUED)
	Debt activity. The following table presents the debt activity of the Partnership for the three months ended March 31, 2015:
	thousands		Carrying Value
	Balance at December 31, 2014		$	2,422,954
	RCF borrowings		140,000
	Repayment of RCF		(30,000		)
	Other		41
	Balance at March 31, 2015		$	2,532,995
Interest Expense Table	The following table summarizes the amounts included in interest expense:
			Three Months Ended
			March 31,
	thousands		2015			2014
	Third parties
	Long-term debt		$	23,342		$	16,135
	Amortization of debt issuance costs and commitment fees		1,292			1,266
	Capitalized interest		(3,094		)	(3,440		)
	Total interest expense – third parties		21,540			13,961
	Affiliates
	Deferred purchase price obligation – Anadarko (1)		1,420			—
	Total interest expense – affiliates		1,420			—
	Interest expense		$	22,960		$	13,961
	(1)	See Note 2 for a discussion of the accretion and present value of the Deferred purchase price obligation - Anadarko.

Description_of_Business_and_Ba3

Description of Business and Basis of Presentation - Asset Table (details)	Mar. 31, 2015
	unit
Operated [Member] | Natural Gas Gathering Systems [Member]
Assets [Line Items]
Assets, number of units	14
Operated [Member] | Natural Gas Treating Facilities [Member]
Assets [Line Items]
Assets, number of units	8
Operated [Member] | Natural Gas Processing Facilities [Member]
Assets [Line Items]
Assets, number of units	13
Operated [Member] | Natural Gas Liquids Pipelines [Member]
Assets [Line Items]
Assets, number of units	3
Operated [Member] | Natural Gas Pipelines [Member]
Assets [Line Items]
Assets, number of units	4
Operated [Member] | Oil Pipelines [Member]
Assets [Line Items]
Assets, number of units	1
Operated Interests [Member] | Natural Gas Gathering Systems [Member]
Assets [Line Items]
Assets, number of units	2
Operated Interests [Member] | Natural Gas Treating Facilities [Member]
Assets [Line Items]
Assets, number of units	5
Operated Interests [Member] | Natural Gas Processing Facilities [Member]
Assets [Line Items]
Assets, number of units	3
Non-Operated Interests [Member] | Natural Gas Gathering Systems [Member]
Assets [Line Items]
Assets, number of units	5
Equity Interests [Member] | Natural Gas Gathering Systems [Member]
Assets [Line Items]
Assets, number of units	2
Equity Interests [Member] | Natural Gas Treating Facilities [Member]
Assets [Line Items]
Assets, number of units	1
Equity Interests [Member] | Natural Gas Processing Facilities [Member]
Assets [Line Items]
Assets, number of units	2
Equity Interests [Member] | Natural Gas Liquids Pipelines [Member]
Assets [Line Items]
Assets, number of units	3
Equity Interests [Member] | Oil Pipelines [Member]
Assets [Line Items]
Assets, number of units	1

Description_of_Business_and_Ba4

Description of Business and Basis of Presentation - Additional Information (details)	1 Months Ended	3 Months Ended	0 Months Ended
	Nov. 30, 2014	Mar. 31, 2015	Mar. 02, 2015
General partner's interest	2.00%
General Partner [Member] | Western Gas Equity Partners [Member]
Percentage acquired		100.00%
Incentive Distribution Rights [Member] | Western Gas Equity Partners [Member]
General partner's interest		100.00%
Non-Operated Marcellus Interest [Member]
Percentage acquired		33.75%
Anadarko-Operated Marcellus Interest [Member]
Percentage acquired		33.75%
Newcastle [Member]
Percentage acquired		50.00%
Delaware Basin JV Gathering LLC [Member]
Percentage acquired		50.00%	50.00%	[1]
Fort Union [Member]
Equity investment ownership		14.81%
Rendezvous [Member]
Equity investment ownership		22.00%
White Cliffs [Member]
Equity investment ownership		10.00%
Mont Belvieu Joint Venture [Member]
Equity investment ownership		25.00%
Texas Express Gathering Limited Liability Company [Member]
Equity investment ownership		20.00%
Texas Express Pipeline Limited Liability Company [Member]
Equity investment ownership		20.00%
Front Range Pipeline Limited Liability Company [Member]
Equity investment ownership		33.33%
[1]	The Partnership acquired Anadarko’s interest in Delaware Basin JV Gathering LLC (“DBJV”), which owns a 50% interest in a gathering system and related facilities (the “DBJV system”). The DBJV system is located in the Delaware Basin in Loving, Ward, Winkler and Reeves Counties, Texas. The Partnership will make a cash payment on March 31, 2020, to Anadarko as consideration for the acquisition of DBJV. The Partnership currently estimates the future payment will be $282.8 million, the net present value of which was $174.3 million as of the acquisition date. See Deferred purchase price obligation - Anadarko below.

Acquisitions_Acquisitions_Tabl

Acquisitions - Acquisitions Table (details) (USD $)

3 Months Ended

0 Months Ended

1 Months Ended

Mar. 31, 2015

Mar. 31, 2014

Mar. 03, 2014

Nov. 25, 2014

Mar. 02, 2015

Nov. 30, 2014

Dec. 31, 2014

Business Acquisition [Line Items]

Borrowings

$140,000,000

$917,742,000

[1]

Units issued

45,711

Table Text Block Supplement [Abstract]

General partner units issued

2,583,068

2,583,068

Texas Express And Front Range [Member]

Business Acquisition [Line Items]

Borrowings

350,000,000

[2]

Cash on hand

6,250,000

[2]

Table Text Block Supplement [Abstract]

General partner units issued

6,296

Texas Express Pipeline Limited Liability Company [Member]

Table Text Block Supplement [Abstract]

Equity investment ownership

20.00%

Texas Express Gathering Limited Liability Company [Member]

Table Text Block Supplement [Abstract]

Equity investment ownership

20.00%

Front Range Pipeline Limited Liability Company [Member]

Table Text Block Supplement [Abstract]

Equity investment ownership

33.33%

Delaware Basin Midstream Limited Liability Company [Member]

Business Acquisition [Line Items]

Percentage acquired

100.00%

[3]

Borrowings

475,000,000

[3]

Cash on hand

298,327,000

[3]

Delaware Basin JV Gathering LLC [Member]

Business Acquisition [Line Items]

Percentage acquired

50.00%

50.00%

[4]

Common Units [Member] | Texas Express And Front Range [Member]

Business Acquisition [Line Items]

Units issued

308,490

[2]

Class C Units [Member]

Business Acquisition [Line Items]

Units issued

45,711

Table Text Block Supplement [Abstract]

Proceeds from the issuance of units

750,000,000

Class C Units [Member] | Delaware Basin Midstream Limited Liability Company [Member]

Business Acquisition [Line Items]

Units issued

10,913,853

[3]

General Partner [Member]

Business Acquisition [Line Items]

Units issued

153,061

[5],[6]

General Partner [Member] | Texas Express And Front Range [Member]

Table Text Block Supplement [Abstract]

Proceeds from the issuance of units

400,000

Affiliated Entity [Member]

Business Acquisition [Line Items]

Cash on hand

1,128,000

360,952,000

[1]

Deferred Purchase Price Obligation - Anadarko [Member] | Affiliated Entity [Member] | Delaware Basin JV Gathering LLC [Member]

Business Acquisition [Line Items]

Deferred purchase price obligation - acquisition date

174,276,000

[4]

Table Text Block Supplement [Abstract]

Future value of deferred purchase price obligation to Anadarko

282,800,000

[1]

Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.

[2]

The Partnership acquired a 20% interest in each of TEG and TEP and a 33.33% interest in FRP from Anadarko. These assets gather and transport NGLs primarily from the Anadarko and Denver-Julesburg (“DJ”) Basins. The interests in these entities are accounted for under the equity method of accounting. In connection with the issuance of the common units, the Partnership’s general partner purchased 6,296 general partner units in exchange for the general partner’s proportionate capital contribution of $0.4 million.

[3]

The Partnership acquired Nuevo Midstream, LLC (“Nuevo”) from a third party. Following the acquisition, the Partnership changed the name of Nuevo to Delaware Basin Midstream, LLC (“DBM”). The assets acquired include cryogenic processing plants, a gas gathering system, and related facilities and equipment, which are collectively referred to as the “DBM complex” and serve production from Reeves, Loving and Culberson Counties, Texas and Eddy and Lea Counties, New Mexico.

[4]

The Partnership acquired Anadarko’s interest in Delaware Basin JV Gathering LLC (“DBJV”), which owns a 50% interest in a gathering system and related facilities (the “DBJV system”). The DBJV system is located in the Delaware Basin in Loving, Ward, Winkler and Reeves Counties, Texas. The Partnership will make a cash payment on March 31, 2020, to Anadarko as consideration for the acquisition of DBJV. The Partnership currently estimates the future payment will be $282.8 million, the net present value of which was $174.3 million as of the acquisition date. See Deferred purchase price obligation - Anadarko below.

[5]

Represents general partner units issued to the general partner in exchange for the general partner’s proportionate capital contribution.

[6]

Includes the issuance of 1,120,153 common units pursuant to the partial exercise of the underwriters’ over-allotment option, the net proceeds from which were $77.0 million. Beginning with this partial exercise, the Partnership’s general partner elected not to make a corresponding capital contribution to maintain its 2.0% interest in the Partnership.

Acquisitions_Impact_to_Histori

Acquisitions - Impact to Historical Consolidated Statement of Income Table (details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Revenues	$375,094		$293,717	[1]
Equity income, net	18,220	[2],[3],[4]	9,251	[1],[2],[3],[4]
Net income	86,794		94,748	[1]
Delaware Basin JV Gathering LLC [Member]
Revenues			14,260
Equity income, net			0
Net income			3,621
Partnership Historical [Member]
Revenues			279,457
Equity income, net			9,251
Net income			$91,127
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[2]	Income earned from equity investments is classified as affiliate. See Note 1.
[3]	Represents amounts earned or incurred on and subsequent to the date of acquisition of the Partnership assets, as well as amounts earned or incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets, recognized under gathering, treating or processing agreements, and purchase and sale agreements.
[4]	Income earned on, distributions from and contributions to equity investments are classified as affiliate. See Note 1.

Acquisitions_Purchase_Price_Al

Acquisitions - Purchase Price Allocation Table (details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Business Acquisition [Line Items]
Goodwill	$393,035	$389,087	[1]
Delaware Basin Midstream Limited Liability Company [Member]
Business Acquisition [Line Items]
Current assets	63,020
Property, plant and equipment	467,171
Goodwill	282,999
Other intangible assets	811,048
Accounts payables	-17,679
Accrued liabilities	-38,684
Deferred income taxes	-1,342
Asset retirement obligations and other	-9,060
Total purchase price	$1,557,473
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.

Acquisitions_Additional_Inform

Acquisitions - Additional Information (details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014		Mar. 02, 2015
Business Acquisition [Line Items]
Deferred purchase price obligation - Anadarko	$175,696,000	[1]			$0	[1],[2]
Delaware Basin Midstream Limited Liability Company [Member]
Business Acquisition [Line Items]
Post-closing purchase price adjustments	3,500,000
Deferred Purchase Price Obligation - Anadarko [Member] | Affiliated Entity [Member]
Business Acquisition [Line Items]
Interest expense, related party	1,420,000	[3]	0	[3]
Deferred Purchase Price Obligation - Anadarko [Member] | Affiliated Entity [Member] | Delaware Basin JV Gathering LLC [Member]
Business Acquisition [Line Items]
Future value of deferred purchase price obligation to Anadarko							282,800,000
Deferred purchase price obligation - acquisition date							174,276,000	[4]
Discount rate percentage	10.00%
Deferred purchase price obligation - Anadarko	175,700,000
Interest expense, related party	$1,400,000
[1]	See Note 2.
[2]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[3]	See Note 2 for a discussion of the accretion and present value of the Deferred purchase price obligation - Anadarko.
[4]	The Partnership acquired Anadarko’s interest in Delaware Basin JV Gathering LLC (“DBJV”), which owns a 50% interest in a gathering system and related facilities (the “DBJV system”). The DBJV system is located in the Delaware Basin in Loving, Ward, Winkler and Reeves Counties, Texas. The Partnership will make a cash payment on March 31, 2020, to Anadarko as consideration for the acquisition of DBJV. The Partnership currently estimates the future payment will be $282.8 million, the net present value of which was $174.3 million as of the acquisition date. See Deferred purchase price obligation - Anadarko below.

Partnership_Distributions_Cash

Partnership Distributions - Cash Distributions Table (details) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014	Mar. 31, 2014
Distributions Made to Members or Limited Partners [Abstract]
Total quarterly distribution per unit	$0.73	[1]	$0.70	$0.63
Total quarterly cash distribution	$133,203	[1]		$98,749
[1]	On April 20, 2015, the Board of Directors of the Partnership’s general partner declared a cash distribution to the Partnership’s unitholders of $0.725 per unit, or $133.2 million in aggregate, including incentive distributions, but excluding distributions on Class C units (see Class C unit distributions below). The cash distribution is payable on May 13, 2015, to unitholders of record at the close of business on April 30, 2015.

Partnership_Distributions_Addi

Partnership Distributions - Additional Information (details) (USD $)	3 Months Ended				0 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014	Mar. 31, 2014	Nov. 25, 2014
Distribution Made to Limited Partner [Line Items]
Partnership agreement day requirement of distribution of available cash	45 days
Total quarterly distribution per unit	$0.73	[1]	$0.70	$0.63
Class C Units [Member]
Distribution Made to Limited Partner [Line Items]
Discount rate percentage					6.00%
PIK Class C unit distributions			45,711
Fair value of PIK Class C unit distributions			$3.10
Prorated period			37 days
[1]	On April 20, 2015, the Board of Directors of the Partnership’s general partner declared a cash distribution to the Partnership’s unitholders of $0.725 per unit, or $133.2 million in aggregate, including incentive distributions, but excluding distributions on Class C units (see Class C unit distributions below). The cash distribution is payable on May 13, 2015, to unitholders of record at the close of business on April 30, 2015.

Equity_and_Partners_Capital_Eq

Equity and Partners' Capital - Equity Offerings Table (details) (USD $)	1 Months Ended		3 Months Ended		12 Months Ended		1 Months Ended
	Nov. 30, 2014		Mar. 31, 2015		Dec. 31, 2014		Apr. 30, 2015	Aug. 31, 2012	Aug. 31, 2014
Capital Unit [Line Items]
Units issued			45,711
Price per unit	$70.85	[1]
Underwriting discount and other offering expenses	$18,615,000	[1]
Net proceeds	602,967,000	[1]
Table Text Block Supplement [Abstract]
General partner's interest	2.00%
Option On Securities [Member]
Capital Unit [Line Items]
Net proceeds	77,000,000
125 Million COP [Member]
Capital Unit [Line Items]
Average price per unit					$73.48	[2]
Underwriting discount and other offering expenses					1,738,000	[2]
Net proceeds					83,245,000	[2]
Table Text Block Supplement [Abstract]
Maximum aggregate principal of common stock								125,000,000
Gross proceeds					85,000,000
500 Million COP [Member]
Capital Unit [Line Items]
Common units issued			480,109
Average price per unit			65.55	[3]
Underwriting discount and other offering expenses			396,000	[3]
Net proceeds			31,076,000	[3]
Table Text Block Supplement [Abstract]
Maximum aggregate principal of common stock									500,000,000
Gross proceeds			31,500,000
Commissions paid			300,000
Common Units [Member]
Capital Unit [Line Items]
Common units issued	8,620,153	[1]
Common Units [Member] | Option On Securities [Member]
Capital Unit [Line Items]
Common units issued	1,120,153
Common Units [Member] | 125 Million COP [Member]
Capital Unit [Line Items]
Common units issued					1,133,384	[2]
Common Units [Member] | 500 Million COP [Member]
Capital Unit [Line Items]
Common units issued			480,109	[3]
Common Units [Member] | 500 Million COP [Member] | Subsequent Event [Member]
Capital Unit [Line Items]
Common units issued							289,744
General Partner [Member]
Capital Unit [Line Items]
Units issued	153,061	[1],[4]
General Partner [Member] | 125 Million COP [Member]
Capital Unit [Line Items]
Units issued					23,132	[2],[4]
[1]	Includes the issuance of 1,120,153 common units pursuant to the partial exercise of the underwriters’ over-allotment option, the net proceeds from which were $77.0 million. Beginning with this partial exercise, the Partnership’s general partner elected not to make a corresponding capital contribution to maintain its 2.0% interest in the Partnership.
[2]	Represents common and general partner units issued during the year ended December 31, 2014, pursuant to the Partnership’s registration statement filed with the SEC in August 2012 authorizing the issuance of up to an aggregate of $125.0 million of common units (the “$125.0 million COP”). Gross proceeds generated (including the general partner’s proportionate capital contributions) during the year ended December 31, 2014, were $85.0 million. The price per unit in the table above represents an average price for all issuances under the $125.0 million COP during the year ended December 31, 2014. As of December 31, 2014, the Partnership had used all the capacity to issue common units under this registration statement.
[3]	Represents common units issued during the three months ended March 31, 2015, pursuant to the Partnership’s registration statement filed with the SEC in August 2014 authorizing the issuance of up to an aggregate of $500.0 million of common units (the “$500.0 million COP”). Gross proceeds generated and commissions paid during the three months ended March 31, 2015, were $31.5 million and $0.3 million, respectively. The price per unit in the table above represents an average price for all issuances under the $500.0 million COP during the three months ended March 31, 2015. Does not include sales of 289,744 common units that settled after March 31, 2015.
[4]	Represents general partner units issued to the general partner in exchange for the general partner’s proportionate capital contribution.

Equity_and_Partners_Capital_Li

Equity and Partners' Capital - Limited Partner and General Partner Units Table (details)	3 Months Ended		1 Months Ended
	Mar. 31, 2015		Nov. 30, 2014		Dec. 31, 2014
Capital Unit [Line Items]
Balance	141,192,051
PIK Class C units	45,711
Long-Term Incentive Plan award vestings	2,014
Balance	141,719,885
500 Million COP [Member]
Capital Unit [Line Items]
Offering	480,109
Common Units [Member]
Capital Unit [Line Items]
Balance	127,695,130
Long-Term Incentive Plan award vestings	2,014
Offering			8,620,153	[1]
Balance	128,177,253
Common Units [Member] | 500 Million COP [Member]
Capital Unit [Line Items]
Offering	480,109	[2]
Class C Units [Member]
Capital Unit [Line Items]
Balance	10,913,853
PIK Class C units	45,711
Balance	10,959,564
General Partner [Member]
Capital Unit [Line Items]
Balance					2,583,068
PIK Class C units			153,061	[1],[3]
Balance	2,583,068				2,583,068
[1]	Includes the issuance of 1,120,153 common units pursuant to the partial exercise of the underwriters’ over-allotment option, the net proceeds from which were $77.0 million. Beginning with this partial exercise, the Partnership’s general partner elected not to make a corresponding capital contribution to maintain its 2.0% interest in the Partnership.
[2]	Represents common units issued during the three months ended March 31, 2015, pursuant to the Partnership’s registration statement filed with the SEC in August 2014 authorizing the issuance of up to an aggregate of $500.0 million of common units (the “$500.0 million COP”). Gross proceeds generated and commissions paid during the three months ended March 31, 2015, were $31.5 million and $0.3 million, respectively. The price per unit in the table above represents an average price for all issuances under the $500.0 million COP during the three months ended March 31, 2015. Does not include sales of 289,744 common units that settled after March 31, 2015.
[3]	Represents general partner units issued to the general partner in exchange for the general partner’s proportionate capital contribution.

Equity_and_Partners_Capital_Ca

Equity and Partners' Capital - Calculation of Net Income Per Unit Table (details) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Earnings Per Unit [Line Items]
Net income attributable to Western Gas Partners, LP	$83,568		$91,056	[1]
Pre-acquisition net (income) loss allocated to Anadarko	-1,742		-2,665	[1]
General partner interest in net (income) loss	-41,993	[2]	-24,834	[1],[2]
Limited partners' interest in net income	39,833	[2]	63,557	[1],[2]
Net income per common unit - basic	$0.26	[3]	$0.54	[1],[3]
Net income per common unit - diluted	$0.26	[3],[4]	$0.54	[1],[3],[4]
Weighted-average limited partnership units outstanding - diluted	138,674		117,716
Common Units [Member]
Earnings Per Unit [Line Items]
Limited partners' interest in net income	32,891	[5]	63,557	[5]
Weighted-average limited partnership units outstanding - basic	127,736		117,716
Class C Units [Member]
Earnings Per Unit [Line Items]
Limited partners' interest in net income	$6,942	[5]	$0	[5]
Weighted-average limited partnership units outstanding - basic	10,938		0
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[2]	Represents net income earned on and subsequent to the date of acquisition of the Partnership assets (as defined in Note 1). See Note 4.
[3]	See Note 4 for the calculation of net income per unit.
[4]	Inclusion of 10,938,232 Class C units in the calculation would have had an anti-dilutive effect.
[5]	Adjusted to reflect amortization for the beneficial conversion feature. See Class C units above for a discussion of the Class C units.

Equity_and_Partners_Capital_Ad

Equity and Partners' Capital - Additional Information (details) (USD $)	1 Months Ended		3 Months Ended	12 Months Ended
In Millions, except Share data, unless otherwise specified	Nov. 30, 2014		Mar. 31, 2015	Dec. 31, 2014
Schedule Of Investments [Line Items]
Units issued			45,711
Price per unit	$70.85	[1]
General partner units owned			2,583,068	2,583,068
General partner's interest	2.00%
Western Gas Equity Partners [Member]
Schedule Of Investments [Line Items]
General partner units owned			2,583,068
General partner's interest			1.80%
Other Subsidiaries Of Anadarko [Member]
Schedule Of Investments [Line Items]
Limited partner ownership interest			8.30%
Class C Units [Member]
Schedule Of Investments [Line Items]
Units issued			45,711
Price per unit	$68.72
Proceeds from the issuance of Class C units	$750
Beneficial conversion feature of Class C units				34.8
Limited partner units owned			10,959,564	10,913,853
Class C Units [Member] | Other Subsidiaries Of Anadarko [Member]
Schedule Of Investments [Line Items]
Units issued	10,913,853
Limited partner units owned			10,959,564
Class C Units [Member] | Maximum [Member]
Schedule Of Investments [Line Items]
Redeemable option on units	$150
Common Units [Member]
Schedule Of Investments [Line Items]
Limited partner units owned			128,177,253	127,695,130
Common Units [Member] | Western Gas Equity Partners [Member]
Schedule Of Investments [Line Items]
Limited partner units owned			49,296,205
Limited partner ownership interest			34.80%
Common Units [Member] | Other Subsidiaries Of Anadarko [Member]
Schedule Of Investments [Line Items]
Limited partner units owned			757,619
Common Units [Member] | Public [Member]
Schedule Of Investments [Line Items]
Limited partner units owned			78,123,429
Limited partner ownership interest			55.10%
Incentive Distribution Rights [Member] | Western Gas Equity Partners [Member]
Schedule Of Investments [Line Items]
General partner's interest			100.00%
[1]	Includes the issuance of 1,120,153 common units pursuant to the partial exercise of the underwriters’ over-allotment option, the net proceeds from which were $77.0 million. Beginning with this partial exercise, the Partnership’s general partner elected not to make a corresponding capital contribution to maintain its 2.0% interest in the Partnership.

Transactions_With_Affiliates_C

Transactions With Affiliates - Commodity Price Swap Agreements Table (details)	Mar. 31, 2015
Ethane [Member] | Year 2016 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	23.11
Ethane [Member] | Minimum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	18.41
Ethane [Member] | Maximum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	23.41
Propane [Member] | Year 2016 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	52.9
Propane [Member] | Minimum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	47.08
Propane [Member] | Maximum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	52.99
Isobutane [Member] | Year 2016 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	73.89
Isobutane [Member] | Minimum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	62.09
Isobutane [Member] | Maximum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	74.02
Normal Butane [Member] | Year 2016 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	64.93
Normal Butane [Member] | Minimum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	54.62
Normal Butane [Member] | Maximum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	65.04
Natural Gasoline [Member] | Year 2016 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	81.68
Natural Gasoline [Member] | Minimum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	72.88
Natural Gasoline [Member] | Maximum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	81.82
Condensate [Member] | Year 2016 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	81.68
Condensate [Member] | Minimum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	76.47
Condensate [Member] | Maximum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	81.82
Natural Gas (per MMbtu) [Member] | Year 2016 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	4.87
Natural Gas (per MMbtu) [Member] | Minimum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	4.66
Natural Gas (per MMbtu) [Member] | Maximum [Member] | Year 2015 [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price	5.96

Transactions_With_Affiliates_G

Transactions With Affiliates - Gains Losses Commodity Price Swap Agreements Table (details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	$21,235		$5,769
Sales [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	55,414	[1]	5,788	[1]
Sales [Member] | Natural Gas [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	10,982	[1]	-3,667	[1]
Sales [Member] | Natural Gas Liquids [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	44,432	[1]	9,455	[1]
Cost of Sales [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	($34,179)	[2]	($19)	[2]
[1]	Reported in affiliate natural gas, natural gas liquids and drip condensate sales in the consolidated statements of income in the period in which the related sale is recorded.
[2]	Reported in cost of product in the consolidated statements of income in the period in which the related purchase is recorded.

Transactions_With_Affiliates_E

Transactions With Affiliates - Equipment Purchases and Sales Table (details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Related Party Transaction [Line Items]
Partners' capital adjustment	$348	($43)	[1]
Affiliated Entity [Member] | Purchases [Member]
Related Party Transaction [Line Items]
Consideration given for equipment	1,128	4,702
Net carrying value	780	4,745
Partners' capital adjustment	$348	($43)
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.

Transactions_With_Affiliates_S

Transactions With Affiliates - Summary Table (details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Related Party Transaction [Line Items]
Revenues	$375,094		$293,717	[1]
Equity income, net	18,220	[2],[3],[4]	9,251	[1],[2],[3],[4]
Cost of product	137,920	[5]	94,376	[1],[5]
Operation and maintenance	56,149	[5]	44,577	[1],[5]
General and administrative	10,512	[5]	8,904	[1],[5]
Operating expenses	283,396		197,176	[1]
Interest income	4,225	[6]	4,225	[1],[6]
Interest expense	22,960	[7]	13,961	[1],[7]
Distributions to unitholders	126,044		92,609	[1]
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Revenues	245,715		214,996	[1]
Cost of product	42,407		18,356
Operation and maintenance	15,376	[8]	12,551	[8]
General and administrative	7,566	[9]	7,303	[9]
Operating expenses	65,349		38,210
Interest expense	1,420	[10]	0	[10]
Distributions to unitholders	$71,695	[11]	$51,882	[11]
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[2]	Income earned from equity investments is classified as affiliate. See Note 1.
[3]	Represents amounts earned or incurred on and subsequent to the date of acquisition of the Partnership assets, as well as amounts earned or incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets, recognized under gathering, treating or processing agreements, and purchase and sale agreements.
[4]	Income earned on, distributions from and contributions to equity investments are classified as affiliate. See Note 1.
[5]	Cost of product includes product purchases from Anadarko (as defined in Note 1) of $42.4 million and $18.4 million for the three months ended March 31, 2015 and 2014, respectively. Operation and maintenance includes charges from Anadarko of $15.4 million and $12.6 million for the three months ended March 31, 2015 and 2014, respectively. General and administrative includes charges from Anadarko of $7.6 million and $7.3 million for the three months ended March 31, 2015 and 2014, respectively. See Note 5.
[6]	Represents interest income recognized on the note receivable from Anadarko.
[7]	Includes affiliate (as defined in Note 1) interest expense of $1.4 million and zero for the three months ended March 31, 2015 and 2014, respectively. See Note 2 and Note 9.
[8]	Represents expenses incurred on and subsequent to the date of the acquisition of the Partnership assets, as well as expenses incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets.
[9]	Represents general and administrative expense incurred on and subsequent to the date of the Partnership’s acquisition of the Partnership assets, as well as a management services fee for reimbursement of expenses incurred by Anadarko for periods prior to the acquisition of the Partnership assets by the Partnership. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see WES LTIP and WGP LTIP and Anadarko Incentive Plans within this Note 5).
[10]	For the three months ended March 31, 2015, includes accretion expense recognized on the Deferred purchase price obligation - Anadarko for the acquisition of DBJV (see Note 2 and Note 9).
[11]	Represents distributions paid under the partnership agreement (see Note 3 and Note 4).

Transactions_With_Affiliates_A

Transactions With Affiliates - Additional Information (details) (USD $)	3 Months Ended		1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	31-May-08	Dec. 31, 2014
Related Party Transaction [Line Items]
Note receivable - Anadarko	$260,000,000			$260,000,000	[1]
Partners' capital adjustment	-160,000
Western Gas Partners Long Term Incentive Plan [Member]
Related Party Transaction [Line Items]
Phantom units vesting period	3 years
Equity-based compensation expense	100,000	100,000
Western Gas Equity Partners Long Term Incentive Plan [Member] | Anadarko Incentive Plans [Member]
Related Party Transaction [Line Items]
Equity-based compensation expense	1,000,000	900,000
Partners' capital adjustment	800,000
Independent Director [Member] | Western Gas Partners Long Term Incentive Plan [Member]
Related Party Transaction [Line Items]
Phantom units vesting period	1 year
Note Receivable From Anadarko [Member]
Related Party Transaction [Line Items]
Note receivable - Anadarko			260,000,000
Note receivable, due date	14-May-38
Fixed annual rate for note receivable bearing interest			6.50%
Fair value of the note receivable	$327,000,000			$317,800,000
Gathering Transportation And Treating [Member]
Related Party Transaction [Line Items]
Affiliate throughput percent	48.00%	49.00%
Processing [Member]
Related Party Transaction [Line Items]
Affiliate throughput percent	52.00%	59.00%
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.

Property_Plant_and_Equipment_H

Property, Plant and Equipment - Historical Cost Table (details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, plant and equipment	5,814,914	$5,626,650	[1]
Accumulated depreciation	1,103,643	1,055,207	[1]
Net property, plant and equipment	4,711,271	4,571,443	[1]
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	3,260	2,884
Gathering Systems [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	5,232,882	4,972,892
Gathering Systems [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Gathering Systems [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	47 years
Pipelines And Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	135,916	151,107
Pipelines And Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	15 years
Pipelines And Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	45 years
Assets Under Construction [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	424,779	483,347
Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	18,077	$16,420
Other [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Other [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	40 years
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.

Property_Plant_and_Equipment_A

Property, Plant and Equipment - Additional Information (details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
Property, Plant and Equipment [Abstract]
Impairment	$8.20

Equity_Investments_Equity_Inve

Equity Investments - Equity Investments Table (details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Schedule of Equity Method Investments [Line Items]
Balance	$634,492	[1]
Investment earnings (loss), net of amortization	18,220	[2],[3],[4]	9,251	[1],[2],[3],[4]
Contributions	4,878		28,462	[1]
Distributions	-18,706	[4]	-10,269	[1],[4]
Distributions in excess of cumulative earnings	-2,964	[4],[5]	-2,044	[1],[4]
Balance	635,920
Fort Union [Member]
Schedule of Equity Method Investments [Line Items]
Balance	25,933
Investment earnings (loss), net of amortization	1,555
Contributions	0
Distributions	-948
Distributions in excess of cumulative earnings	0	[5]
Balance	26,540
White Cliffs [Member]
Schedule of Equity Method Investments [Line Items]
Balance	44,315
Investment earnings (loss), net of amortization	3,980
Contributions	2,917
Distributions	-3,834
Distributions in excess of cumulative earnings	-902	[5]
Balance	46,476
Rendezvous [Member]
Schedule of Equity Method Investments [Line Items]
Balance	56,336
Investment earnings (loss), net of amortization	377
Contributions	0
Distributions	-862
Distributions in excess of cumulative earnings	-736	[5]
Balance	55,115
Mont Belvieu Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Balance	121,337
Investment earnings (loss), net of amortization	5,791
Contributions	-432
Distributions	-6,291
Distributions in excess of cumulative earnings	0	[5]
Balance	120,405
Texas Express Gathering Limited Liability Company [Member]
Schedule of Equity Method Investments [Line Items]
Balance	16,790
Investment earnings (loss), net of amortization	190
Contributions	0
Distributions	-337
Distributions in excess of cumulative earnings	0	[5]
Balance	16,643
Texas Express Pipeline Limited Liability Company [Member]
Schedule of Equity Method Investments [Line Items]
Balance	198,793
Investment earnings (loss), net of amortization	3,616
Contributions	1,180
Distributions	-3,679
Distributions in excess of cumulative earnings	-581	[5]
Balance	199,329
Front Range Pipeline Limited Liability Company [Member]
Schedule of Equity Method Investments [Line Items]
Balance	170,988
Investment earnings (loss), net of amortization	2,711
Contributions	1,213
Distributions	-2,755
Distributions in excess of cumulative earnings	-745	[5]
Balance	$171,412
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[2]	Income earned from equity investments is classified as affiliate. See Note 1.
[3]	Represents amounts earned or incurred on and subsequent to the date of acquisition of the Partnership assets, as well as amounts earned or incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets, recognized under gathering, treating or processing agreements, and purchase and sale agreements.
[4]	Income earned on, distributions from and contributions to equity investments are classified as affiliate. See Note 1.
[5]	Distributions in excess of cumulative earnings, classified as investing cash flows in the consolidated statements of cash flows, is calculated on an individual investment basis.

Components_of_Working_Capital_1

Components of Working Capital - Other Current Assets Table (details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, unless otherwise specified
Other Current Assets [Line Items]
Natural gas liquids inventory	$6,087		$5,316
Natural gas imbalance receivables	1,682		415
Prepaid insurance	1,416		2,443
Other	1,295		1,893
Total other current assets	$10,480	[1]	$10,067	[1],[2]
[1]	Other current assets includes natural gas imbalance receivables from affiliates of zero and $0.2 million as of March 31, 2015, and December 31, 2014, respectively.
[2]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.

Components_of_Working_Capital_2

Components of Working Capital - Accrued Liabilities Table (details) (USD $)	3 Months Ended
	Mar. 31, 2015		Dec. 31, 2014
Accrued Liabilities [Line Items]
Accrued interest expense	$27,995,000		$24,741,000
Short-term asset retirement obligations	5,739,000		1,224,000
Short-term remediation and reclamation obligations	475,000		475,000
Income taxes payable	299,000		207,000
Total accrued liabilities	171,609,000		170,789,000	[1]
Delaware Basin Midstream Limited Liability Company [Member]
Table Text Block Supplement [Abstract]
Post-closing purchase price adjustments	3,500,000
Accrued Capital Expenditures [Member]
Accrued Liabilities [Line Items]
Other accrued liabilities	94,176,000		128,856,000
Accrued Plant Purchases [Member]
Accrued Liabilities [Line Items]
Other accrued liabilities	37,826,000		14,023,000
Other Accrued Liabilities [Member]
Accrued Liabilities [Line Items]
Other accrued liabilities	$5,099,000	[2]	$1,263,000	[2]
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[2]	Includes $3.5 million of post-closing purchase price adjustments at March 31, 2015, related to the acquisition of DBM.

Debt_and_Interest_Expense_Debt

Debt and Interest Expense - Debt Outstanding Table (details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
Debt Instrument [Line Items]
Total long-term debt principal	$2,540,000,000		$2,430,000,000
Carrying Value	2,532,995,000		2,422,954,000	[1]
Fair Value	2,647,557,000	[2]	2,511,253,000	[2]
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal	620,000,000		510,000,000
Carrying Value	620,000,000		510,000,000
Fair Value	620,000,000	[2]	510,000,000	[2]
Senior Notes [Member] | 5.375% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Principal	500,000,000		500,000,000
Carrying Value	495,854,000		495,714,000
Fair Value	555,175,000	[2]	549,530,000	[2]
Senior Notes [Member] | 4.000% Senior Notes due 2022 [Member]
Debt Instrument [Line Items]
Principal	670,000,000		670,000,000
Carrying Value	672,841,000		672,930,000
Fair Value	683,554,000	[2]	681,942,000	[2]
Senior Notes [Member] | 2.600% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Principal	350,000,000		350,000,000
Carrying Value	350,443,000		350,474,000
Fair Value	355,372,000	[2]	352,162,000	[2]
Senior Notes [Member] | 5.450% Senior Notes due 2044 [Member]
Debt Instrument [Line Items]
Principal	400,000,000		400,000,000
Carrying Value	393,857,000		393,836,000
Fair Value	$433,456,000	[2]	$417,619,000	[2]
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[2]	Fair value is measured using Level 2 inputs.

Debt_and_Interest_Expense_Debt1

Debt and Interest Expense - Debt Activity Table (details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015
Debt Instrument [Line Items]
Beginning balance	$2,422,954	[1]
Other	41
Ending balance	2,532,995
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Beginning balance	510,000
Borrowings	140,000
Repayment	-30,000
Ending balance	$620,000
[1]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.

Debt_and_Interest_Expense_Inte

Debt and Interest Expense - Interest Expense Table (details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Debt Instrument [Line Items]
Interest expense	$22,960	[1]	$13,961	[1],[2]
Third Parties [Member]
Debt Instrument [Line Items]
Long-term debt	23,342		16,135
Amortization of debt issuance costs and commitment fees	1,292		1,266
Capitalized interest	-3,094		-3,440
Interest expense	21,540		13,961
Affiliated Entity [Member]
Debt Instrument [Line Items]
Interest expense	1,420	[3]	0	[3]
Affiliated Entity [Member] | Deferred Purchase Price Obligation - Anadarko [Member]
Debt Instrument [Line Items]
Interest expense, related party	$1,420	[4]	$0	[4]
[1]	Includes affiliate (as defined in Note 1) interest expense of $1.4 million and zero for the three months ended March 31, 2015 and 2014, respectively. See Note 2 and Note 9.
[2]	Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.
[3]	For the three months ended March 31, 2015, includes accretion expense recognized on the Deferred purchase price obligation - Anadarko for the acquisition of DBJV (see Note 2 and Note 9).
[4]	See Note 2 for a discussion of the accretion and present value of the Deferred purchase price obligation - Anadarko.

Debt_and_Interest_Expense_Addi

Debt and Interest Expense - Additional Information (details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facility, expiration date	26-Feb-19
Facility, interest rate at period end	1.48%	1.47%
Facility, fee rate	0.20%	0.20%
Facility, outstanding borrowings	$620,000,000
Outstanding letters of credit	12,800,000
Facility, available borrowing capacity	$567,200,000
Senior Notes [Member] | 5.375% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Fixed interest rate	5.38%
Debt instrument, maturity date	1-Jun-21
Senior Notes [Member] | 4.000% Senior Notes due 2022 [Member]
Debt Instrument [Line Items]
Fixed interest rate	4.00%
Debt instrument, maturity date	1-Jul-22
Senior Notes [Member] | 2.600% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Fixed interest rate	2.60%
Debt instrument, maturity date	15-Aug-18
Senior Notes [Member] | 5.450% Senior Notes due 2044 [Member]
Debt Instrument [Line Items]
Fixed interest rate	5.45%
Debt instrument, maturity date	1-Apr-44

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Committed capital	$24.10
Rent expense associated with office, warehouse and equipment leases	$4.20	$2.30