Western Midstream Partners 10-K 26 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Billions, except Share data, unless otherwise specified	Dec. 31, 2014	Feb. 23, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Trading Symbol	WES
Entity Registrant Name	Western Gas Partners LP
Entity Central Index Key	1414475
Document Type	10-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$5.20
Entity Common Units Outstanding		127,695,130

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Revenues
Total revenues	$1,273,763		$1,029,763		$894,476
Equity income, net	57,836	[1],[2],[3]	22,948	[1],[2],[3]	16,042	[1],[2],[3]
Operating expenses
Cost of product	437,956	[4]	364,285	[4]	336,079	[4]
Operation and maintenance	199,305	[4]	168,657	[4]	140,106	[4]
General and administrative	34,242	[4]	29,751	[4]	99,212	[4]
Property and other taxes	25,353		23,244		19,688
Depreciation, amortization and impairments	183,156		145,916		120,608
Total operating expenses	880,012		731,853		715,693
Operating income	451,587		320,858		194,825
Interest income - affiliates	16,900	[5]	16,900	[5]	16,900	[5]
Interest expense	-76,766	[6]	-51,797	[6]	-42,060	[6]
Other income (expense), net	864		1,837		292
Income before income taxes	392,585		287,798		169,957
Income tax (benefit) expense	2,027		2,355		20,690
Net income	390,558		285,443		149,267
Net income attributable to noncontrolling interests	14,025		10,816		14,890
Net income attributable to Western Gas Partners, LP	376,533		274,627		134,377
Limited partners' interest in net income:
Pre-acquisition net (income) loss allocated to Anadarko	956		-4,128		-27,391
General partner interest in net (income) loss	-120,980	[7]	-69,633	[7]	-28,089	[7]
Limited partners' interest in net income	256,509	[7]	200,866	[7]	78,897	[7]
Net income per common unit - basic	$2.13	[8]	$1.83	[8]	$0.84	[8]
Net income per common unit - diluted	$2.12	[8]	$1.83	[8]	$0.84	[8]
Affiliated Entity [Member]
Revenues
Gathering, processing and transportation of natural gas and natural gas liquids	394,870		306,810		249,997
Natural gas, natural gas liquids and condensate sales	570,047		496,848		436,423
Other	5,078		1,868		1,606
Total revenues	969,995	[1]	805,526	[1]	688,026	[1]
Operating expenses
Cost of product	114,000	[1]	129,045	[1]	145,250	[1]
Operation and maintenance	58,884	[9]	56,435	[9]	51,237	[9]
General and administrative	26,989	[10]	23,354	[10]	92,847	[10]
Total operating expenses	199,873		208,834		289,334
Interest expense	0	[11]	0	[11]	-2,766	[11]
Third Parties [Member]
Revenues
Gathering, processing and transportation of natural gas and natural gas liquids	252,581		175,732		132,333
Natural gas, natural gas liquids and condensate sales	42,807		44,396		71,916
Other	8,380		4,109		2,201
Total revenues	$303,768		$224,237		$206,450
[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]	Income earned on, distributions from and contributions to equity investments are classified as affiliate. See Note 1.
[3]	Income earned from equity investments is classified as affiliate. See Note 1.
[4]	Cost of product includes product purchases from Anadarko (as defined in Note 1) of $114.0 million, $129.0 million and $145.3 million for the years ended December 31, 2014, 2013 and 2012, respectively. Operation and maintenance includes charges from Anadarko of $58.9 million, $56.4 million and $51.2 million for the years ended December 31, 2014, 2013 and 2012, respectively. General and administrative includes charges from Anadarko of $27.0 million, $23.4 million and $92.8 million for the years ended December 31, 2014, 2013 and 2012, respectively. See Note 5.
[5]	Represents interest income recognized on the note receivable from Anadarko.
[6]	Includes affiliate (as defined in Note 1) interest expense of zero for each of the years ended December 31, 2014 and 2013, and $2.8 million for the year ended December 31, 2012. See Note 12.
[7]	Represents net income earned on and subsequent to the date of acquisition of the Partnership assets (as defined in Note 1). See Note 4.
[8]	See Note 4 for the calculation of net income per unit.
[9]	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.
[10]	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, WGP LTIP and Anadarko Incentive Plans, and The Incentive Plan within this Note 5).
[11]	For the year ended December 31, 2012, includes interest expense recognized on the note payable to Anadarko (see Note 12) and interest imputed on the reimbursement payable to Anadarko for certain expenditures Anadarko incurred in 2011 related to the construction of the Brasada complex and Lancaster plant. The Partnership repaid the note payable to Anadarko in June 2012, and repaid the reimbursement payable to Anadarko associated with the construction of the Brasada complex and Lancaster plant in the fourth quarter of 2012.

Consolidated_Statements_of_Inc1

Consolidated Statements of Income (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Cost of product	$437,956	[1]	$364,285	[1]	$336,079	[1]
Operation and maintenance	199,305	[1]	168,657	[1]	140,106	[1]
General and administrative	34,242	[1]	29,751	[1]	99,212	[1]
Interest expense	76,766	[2]	51,797	[2]	42,060	[2]
Affiliated Entity [Member]
Cost of product	114,000	[3]	129,045	[3]	145,250	[3]
Operation and maintenance	58,884	[4]	56,435	[4]	51,237	[4]
General and administrative	26,989	[5]	23,354	[5]	92,847	[5]
Interest expense	$0	[6]	$0	[6]	$2,766	[6]
[1]	Cost of product includes product purchases from Anadarko (as defined in Note 1) of $114.0 million, $129.0 million and $145.3 million for the years ended December 31, 2014, 2013 and 2012, respectively. Operation and maintenance includes charges from Anadarko of $58.9 million, $56.4 million and $51.2 million for the years ended December 31, 2014, 2013 and 2012, respectively. General and administrative includes charges from Anadarko of $27.0 million, $23.4 million and $92.8 million for the years ended December 31, 2014, 2013 and 2012, respectively. See Note 5.
[2]	Includes affiliate (as defined in Note 1) interest expense of zero for each of the years ended December 31, 2014 and 2013, and $2.8 million for the year ended December 31, 2012. See Note 12.
[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]	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, WGP LTIP and Anadarko Incentive Plans, and The Incentive Plan within this Note 5).
[6]	For the year ended December 31, 2012, includes interest expense recognized on the note payable to Anadarko (see Note 12) and interest imputed on the reimbursement payable to Anadarko for certain expenditures Anadarko incurred in 2011 related to the construction of the Brasada complex and Lancaster plant. The Partnership repaid the note payable to Anadarko in June 2012, and repaid the reimbursement payable to Anadarko associated with the construction of the Brasada complex and Lancaster plant in the fourth quarter of 2012.

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014		Dec. 31, 2013
Current assets
Cash and cash equivalents	$67,054,000		$100,728,000
Accounts receivable, net	98,114,000	[1]	84,060,000	[1]
Other current assets	10,067,000	[2]	10,022,000	[2]
Total current assets	175,235,000		194,810,000
Note receivable - Anadarko	260,000,000		260,000,000
Property, plant and equipment
Cost	5,424,699,000		4,239,100,000
Less accumulated depreciation	1,040,328,000		855,845,000
Net property, plant and equipment	4,384,371,000		3,383,255,000
Goodwill	384,387,000		105,336,000
Other intangible assets	884,857,000		53,606,000
Equity investments	634,492,000		593,400,000
Other assets	28,289,000		27,401,000
Total assets	6,751,631,000		4,617,808,000
Current liabilities
Accounts and natural gas imbalance payables	29,104,000	[3]	39,589,000	[3]
Accrued ad valorem taxes	14,812,000		13,860,000
Accrued liabilities	158,655,000	[4]	137,011,000	[4]
Total current liabilities	202,571,000		190,460,000
Long-term debt	2,422,954,000		1,418,169,000
Deferred income taxes	4,171,000		37,998,000
Asset retirement obligations and other	110,069,000		79,145,000
Total long-term liabilities	2,537,194,000		1,535,312,000
Total liabilities	2,739,765,000		1,725,772,000
Equity and partners' capital
General partner units (2,583,068 and 2,394,345 units issued and outstanding at December 31, 2014, and December 31, 2013, respectively)	105,725,000		78,157,000
Net investment by Anadarko	0		312,092,000
Total partners' capital	3,942,396,000		2,821,442,000
Noncontrolling interest	69,470,000		70,594,000
Total equity and partners' capital	4,011,866,000		2,892,036,000
Total liabilities, equity and partners' capital	6,751,631,000		4,617,808,000
Class C Units [Member]
Equity and partners' capital
Common units (127,695,130 and 117,322,812 units issued and outstanding at December 31, 2014 and 2013, respectively) and Class C Units (10,913,853 and zero units issued and outstanding at December 31, 2014 and 2013, respectively)	716,957,000		0
Common Units [Member]
Equity and partners' capital
Common units (127,695,130 and 117,322,812 units issued and outstanding at December 31, 2014 and 2013, respectively) and Class C Units (10,913,853 and zero units issued and outstanding at December 31, 2014 and 2013, respectively)	$3,119,714,000		$2,431,193,000
[1]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $64.7 million and $47.9 million as of December 31, 2014 and 2013, respectively.
[2]	Other current assets includes natural gas imbalance receivables from affiliates of $0.2 million and $0.1 million as of December 31, 2014 and 2013, respectively.
[3]	Accounts and natural gas imbalance payables includes amounts payable to affiliates of $0.1 million and $2.3 million as of December 31, 2014 and 2013, respectively.
[4]	Accrued liabilities includes amounts payable to affiliates of zero and $0.1 million as of December 31, 2014 and 2013, respectively.

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
General partner units issued	2,583,068		2,394,345
General partner units outstanding	2,583,068		2,394,345
Accounts receivable, net	$98,114	[1]	$84,060	[1]
Other current assets	10,067	[2]	10,022	[2]
Accounts and natural gas imbalance payables	29,104	[3]	39,589	[3]
Accrued liabilities	158,655	[4]	137,011	[4]
Common Units [Member]
Common units issued	127,695,130		117,322,812
Common units outstanding	127,695,130		117,322,812
Class C Units [Member]
Common units issued	10,913,853		0
Common units outstanding	10,913,853		0
Affiliated Entity [Member]
Accounts receivable, net	64,700		47,900
Other current assets	200		100
Accounts and natural gas imbalance payables	100		2,300
Accrued liabilities	$0		$100
[1]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $64.7 million and $47.9 million as of December 31, 2014 and 2013, respectively.
[2]	Other current assets includes natural gas imbalance receivables from affiliates of $0.2 million and $0.1 million as of December 31, 2014 and 2013, respectively.
[3]	Accounts and natural gas imbalance payables includes amounts payable to affiliates of $0.1 million and $2.3 million as of December 31, 2014 and 2013, respectively.
[4]	Accrued liabilities includes amounts payable to affiliates of zero and $0.1 million as of December 31, 2014 and 2013, 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]	Chipeta Processing Limited Liability Company [Member]		Chipeta Processing Limited Liability Company [Member]		Chipeta Processing Limited Liability Company [Member]		Chipeta Processing Limited Liability Company [Member]
In Thousands										Common Units [Member]		General Partner Units [Member]		Noncontrolling Interest [Member]
Balance at Dec. 31, 2011		$2,010,279	$362,573	$1,495,253		$31,729	$120,724
Net income (loss)		149,267	27,391	78,897		28,089	14,890
Issuance of common and general partner units, net of offering expenses		625,877		613,188		12,689
Contributions from noncontrolling interest owners		29,108					29,108
Distributions to noncontrolling interest owner		-17,303					-17,303
Distributions to unitholders		-197,850		-175,639		-22,211
Acquisitions from affiliates		-458,764	-482,701	23,458		479		-121,104	[1]	-44,071	[1]	162	[1]	-77,195	[1]
Contributions of equity-based compensation from Anadarko	[2]	87,057		84,971		2,086
Net pre-acquisition contributions from (distributions to) Anadarko		193,236	299,833	-106,597
Net distributions to Anadarko of other assets		-15,296		-15,002		-273	-21
Elimination of net deferred tax liabilities		-106,504	-106,504
Other		3,065		2,608		2	455
Balance at Dec. 31, 2012		2,394,076	313,600	1,957,066		52,752	70,658
Net income (loss)		285,443	4,128	200,866		69,633	10,816
Issuance of common and general partner units, net of offering expenses		740,586		724,811		15,775
Contributions from noncontrolling interest owners		2,247					2,247
Distributions to noncontrolling interest owner		-13,127					-13,127
Distributions to unitholders		-299,101		-239,157		-59,944
Acquisitions from affiliates		-465,500	-255,635	-209,865
Contributions of equity-based compensation from Anadarko	[2]	2,923		2,865		58
Net pre-acquisition contributions from (distributions to) Anadarko	[3]	203,469	203,469
Net distributions to Anadarko of other assets		-5,855		-5,738		-117
Elimination of net deferred tax liabilities		46,530	46,530
Other		345		345
Balance at Dec. 31, 2013		2,892,036	312,092	2,431,193		78,157	70,594
Net income (loss)		390,558	-956	254,737	1,772	120,980	14,025
Issuance of common and general partner units, net of offering expenses		704,728		691,417		13,311
Issuance of Class C units		750,000			750,000
Beneficial conversion feature of Class C units		0		34,815	-34,815
Distributions to noncontrolling interest owner		-15,149					-15,149
Distributions to unitholders		-408,621		-302,049		-106,572
Acquisitions from affiliates		-356,250	-372,784	16,534
Contributions of equity-based compensation from Anadarko	[2]	3,167		3,104		63
Net pre-acquisition contributions from (distributions to) Anadarko	[3]	23,488	23,488
Net distributions to Anadarko of other assets		-10,733		-10,519		-214
Elimination of net deferred tax liabilities		-38,160	-38,160
Other		482		482
Balance at Dec. 31, 2014		$4,011,866	$0	$3,119,714	$716,957	$105,725	$69,470
[1]	See Note 2 for a description of the acquisition of Anadarko’s then-remaining 24% membership interest in Chipeta in August 2012. The$43.9 million decrease to partners’ capital resulting from the August 2012 Chipeta acquisition, together with net income attributable to Western Gas Partners, LP, totaled $90.5 million for the year ended December 31, 2012.
[2]	Associated with the Anadarko Incentive Plans for the years ended December 31, 2014, 2013 and 2012 and the Incentive Plan for the year ended December 31, 2012, as defined and described in Note 1 and Note 5.
[3]	Includes deferred taxes on capitalized interest of $0.3 million and $5.5 million associated with the acquisition of the TEFR Interests (as defined and described in Note 1) for the years ended December 31, 2014 and 2013, respectively.

Consolidated_Statement_of_Equi1

Consolidated Statement of Equity and Partners Capital (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012		Aug. 31, 2012
Acquisitions from affiliates	($356,250,000)	($465,500,000)	($458,764,000)
The decrease to Partners' capital resulting from the August 2012 Chipeta acquisition together with Net income attributable to Western Gas Partners, LP			90,500,000
Deferred taxes on capitalized interest	-38,160,000	46,530,000	-106,504,000
Chipeta Processing Limited Liability Company [Member]
Ownership interest by noncontrolling owner	25.00%
Acquisitions from affiliates			-121,104,000	[1]
Affiliated Entity [Member] | Chipeta Processing Limited Liability Company [Member]
Ownership interest by noncontrolling owner					24.00%
Partnership Interest [Member] | Chipeta Processing Limited Liability Company [Member]
Acquisitions from affiliates			43,900,000
Net Investment by Anadarko [Member]
Acquisitions from affiliates	-372,784,000	-255,635,000	-482,701,000
Deferred taxes on capitalized interest	-38,160,000	46,530,000	-106,504,000
Net Investment by Anadarko [Member] | Capitalized Interest [Member]
Deferred taxes on capitalized interest	$300,000	$5,500,000
[1]	See Note 2 for a description of the acquisition of Anadarko’s then-remaining 24% membership interest in Chipeta in August 2012. The$43.9 million decrease to partners’ capital resulting from the August 2012 Chipeta acquisition, together with net income attributable to Western Gas Partners, LP, totaled $90.5 million for the year ended December 31, 2012.

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Cash flows from operating activities
Net income	$390,558		$285,443		$149,267
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and impairments	183,156		145,916		120,608
Non-cash equity-based compensation expense	3,920		3,521		3,717
Deferred income taxes	2,583		31,891		30,109
Debt-related amortization and other items, net	2,736		2,449		2,319
Equity income, net	-57,836	[1],[2],[3]	-22,948	[1],[2],[3]	-16,042	[1],[2],[3]
Distributions from equity investment earnings	62,967	[1]	17,698	[1]	20,660	[1]
Changes in assets and liabilities:
(Increase) decrease in accounts receivable, net	-4,217		-34,019		22,916
Increase (decrease) in accounts and natural gas imbalance payables and accrued liabilities, net	-52,530		21,952		5,045
Change in other items, net	3,470		-3,702		-552
Net cash provided by operating activities	534,807		448,201		338,047
Cash flows from investing activities
Capital expenditures	-673,004		-646,471		-638,121
Acquisitions			-78,129
Investments in equity affiliates	-64,278		-294,693		-108,457
Distributions from equity investments in excess of cumulative earnings	18,055	[1],[4]	4,438	[1],[4]	0	[1]
Net cash used in investing activities	-2,621,559		-1,652,995		-1,357,537
Cash flows from financing activities
Borrowings, net of debt issuance costs	1,646,878		957,503		1,041,648
Repayments of debt	-650,000		-710,000		-549,000
Increase (decrease) in outstanding checks	1,693		-1,763		1,800
Proceeds from the issuance of common and general partner units, net of offering expenses	704,489		740,825		625,877
Distributions to unitholders	-408,621		-299,101		-197,850
Contributions from noncontrolling interest owners	0		2,247		29,108
Distributions to noncontrolling interest owners	-15,149		-13,127		-17,303
Net contributions from Anadarko	23,788		208,957		278,632
Net cash provided by financing activities	2,053,078		885,541		1,212,912
Net increase (decrease) in cash and cash equivalents	-33,674		-319,253		193,422
Cash and cash equivalents at beginning of period	100,728		419,981		226,559
Cash and cash equivalents at end of period	67,054		100,728		419,981
Supplemental disclosures
Net distributions to Anadarko of other assets	10,733		5,855		15,296
Interest paid, net of capitalized interest	67,648		47,098		28,042
Taxes paid (reimbursements received)	-90		552		495
Capital lease asset transfer	4,833	[5]	0	[5]	0	[5]
Class C Units [Member]
Cash flows from financing activities
Proceeds from the issuance of Class C units	750,000		0		0
Affiliated Entity [Member]
Cash flows from investing activities
Contributions in aid of construction costs from affiliates	183		617		0
Acquisitions	-379,193		-476,711		-611,719
Proceeds from the sale of assets	0		85		760
Cash flows from financing activities
Distributions to unitholders	-234,024	[6]	-169,150	[6]	-98,280	[6]
Contributions from noncontrolling interest owners	0	[7]	0	[7]	12,588	[7]
Distributions to noncontrolling interest owners	0	[7]	0	[7]	-6,528	[7]
Third Parties [Member]
Cash flows from investing activities
Acquisitions	-1,523,327		-240,274		0
Proceeds from the sale of assets	$5		$14		$0
[1]	Income earned on, distributions from and contributions to equity investments are classified as affiliate. See Note 1.
[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]	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.
[5]	For the year ended December 31, 2014, represents transfers of $4.6 million from other long-term assets, associated with the capital lease components of a processing agreement. See Note 7.
[6]	Represents distributions paid under the partnership agreement (see Note 3 and Note 4).
[7]	As described in Note 2, the Partnership acquired the additional Chipeta interest on August 1, 2012, and accounted for the acquisition on a prospective basis. As such, contributions from noncontrolling interest owners and distributions to noncontrolling interest owners subsequent to the acquisition date no longer reflect contributions from or distributions to Anadarko.

Consolidated_Statements_of_Cas1

Consolidated Statements of Cash Flows (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2014
In Thousands, unless otherwise specified
Property, plant and equipment	$5,424,699	$4,239,100
Natural Gas Processing Plant [Member]
Property, plant and equipment	$4,600		$4,600

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Significant Accounting Policies	1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	General. Western Gas Partners, LP is a growth-oriented Delaware master limited partnership formed by Anadarko Petroleum Corporation in 2007 to own, operate, acquire and develop midstream energy assets. The Partnership closed its initial public offering (“IPO”) to become publicly traded in 2008.
	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”) (see Note 2). The interests in TEP, TEG and FRP are referred to collectively as the “TEFR Interests.” All income earned on, distributions from and contributions to, the Partnership’s equity investments are considered to be affiliate transactions. “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 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 December 31, 2014, 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	1	5	2
	Natural gas treating facilities	8	—	—	1
	Natural gas processing facilities	13	3	—	2
	NGL pipelines	3	—	—	3
	Natural gas pipelines	4	—	—	—
	Oil pipeline	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.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
	Western Gas Equity Partners, LP. In December 2012, WGP completed its IPO of 19,758,150 common units representing limited partner interests in WGP at a price of $22.00 per common unit. WGP used the net proceeds from the offering to purchase common and general partner units of the Partnership resulting in aggregate proceeds to the Partnership of $409.4 million, which was used by the Partnership for general partnership purposes, including the funding of capital expenditures.
	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. 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.
	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 (see Note 2) and its 50% share of the assets, liabilities, revenues and expenses attributable to the Newcastle system in the accompanying consolidated financial statements.
	In July 2009, the Partnership acquired a 51% interest in Chipeta Processing LLC (“Chipeta”) and became party to Chipeta’s limited liability company agreement (the “Chipeta LLC agreement”). On August 1, 2012, the Partnership acquired Anadarko’s then-remaining 24% membership interest in Chipeta (the “additional Chipeta interest”). Prior to this transaction, the interests in Chipeta held by Anadarko and a third-party member were reflected as noncontrolling interests in the consolidated financial statements. The acquisition of the additional Chipeta interest was accounted for on a prospective basis as the Partnership acquired an additional interest in an already-consolidated entity. As such, effective August 1, 2012, noncontrolling interest excludes the financial results and operations of the additional Chipeta interest. The remaining 25% membership interest held by the third-party member is reflected within noncontrolling interests in the consolidated financial statements for all periods presented. See Note 2.
	Presentation of Partnership assets. The term “Partnership assets” refers to the assets owned and interests accounted for under the equity method (see Note 9) by the Partnership as of December 31, 2014. 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 (see Note 2). 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.
	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.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
	Use of estimates. 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 under the particular circumstances. 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.
	Fair value. The fair-value-measurement standard defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The standard characterizes inputs used in determining fair value according to a hierarchy that prioritizes those inputs based upon the degree to which they are observable. The three levels of the fair value hierarchy are as follows:
	Level 1 – Inputs represent quoted prices in active markets for identical assets or liabilities.
	Level 2 – Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly (for example, quoted market prices for similar assets or liabilities in active markets or quoted market prices for identical assets or liabilities in markets not considered to be active, inputs other than quoted prices that are observable for the asset or liability, or market-corroborated inputs).
	Level 3 – Inputs that are not observable from objective sources, such as management’s internally developed assumptions used in pricing an asset or liability (for example, an estimate of future cash flows used in management’s internally developed present value of future cash flows model that underlies the fair value measurement).
	Nonfinancial assets and liabilities initially measured at fair value include certain assets and liabilities acquired in a third-party business combination, assets and liabilities exchanged in non-monetary transactions, long-lived assets (asset groups), goodwill and other intangibles, initial recognition of asset retirement obligations, and initial recognition of environmental obligations assumed in a third-party acquisition. Impairment analyses for long-lived assets, goodwill and other intangibles, and the initial recognition of asset retirement obligations and environmental obligations use Level 3 inputs. When the Partnership is required to measure fair value and there is not a market-observable price for the asset or liability or a market-observable price for a similar asset or liability, the Partnership uses the cost, income, or market valuation approach depending on the quality of information available to support management’s assumptions.
	The fair value of debt reflects any premium or discount for the difference between the stated interest rate and the quarter-end market interest rate, and is based on quoted market prices for identical instruments, if available, or based on valuations of similar debt instruments. See Note 12.
	The carrying amounts of cash and cash equivalents, accounts receivable and accounts payable reported on the consolidated balance sheets approximate fair value due to the short-term nature of these items.
	Cash equivalents. The Partnership considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents.
	1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
	Bad-debt reserve. The Partnership’s revenues are primarily from Anadarko, for which no credit limit is maintained. The Partnership analyzes its exposure to bad debts on a customer-by-customer basis for its third-party accounts receivable and may establish credit limits for significant third-party customers. As of December 31, 2014 and 2013, the Partnership’s bad-debt reserve was immaterial.
	Natural gas imbalances. The consolidated balance sheets include natural gas imbalance receivables and payables resulting from differences in gas volumes received into the Partnership’s systems and gas volumes delivered by the Partnership to customers’ pipelines. Natural gas volumes owed to or by the Partnership that are subject to monthly cash settlement are valued according to the terms of the contract as of the balance sheet dates and reflect market index prices. Other natural gas volumes owed to or by the Partnership are valued at the Partnership’s weighted-average cost of natural gas as of the balance sheet dates and are settled in-kind. As of December 31, 2014, natural gas imbalance receivables and payables were $0.4 million and $0.7 million, respectively. As of December 31, 2013, natural gas imbalance receivables and payables were $3.6 million and $2.5 million, respectively. Changes in natural gas imbalances are reported in other revenues for imbalance receivables or in cost of product for imbalance payables.
	Inventory. The cost of NGLs inventories is determined by the weighted-average cost method on a location-by-location basis. Inventory is stated at the lower of weighted-average cost or market value and is reported in other current assets in the consolidated balance sheets. See Note 10.
	Property, plant and equipment. Property, plant and equipment are generally stated at the lower of historical cost less accumulated depreciation or fair value, if impaired. Because acquisitions of assets from Anadarko are transfers of net assets between entities under common control, the assets acquired from Anadarko are initially recorded at Anadarko’s historic carrying value. The difference between the carrying value of net assets acquired from Anadarko and the consideration paid is recorded as an adjustment to partners’ capital.
	Assets acquired in a business combination or non-monetary exchange with a third party are initially recorded at fair value. All construction-related direct labor and material costs are capitalized. The cost of renewals and betterments that extend the useful life of property, plant and equipment is also capitalized. The cost of repairs, replacements and major maintenance projects that do not extend the useful life or increase the expected output of property, plant and equipment is expensed as incurred.
	Depreciation is computed using the straight-line method based on estimated useful lives and salvage values of assets. However, subsequent events could cause a change in estimates, thereby impacting future depreciation amounts. Uncertainties that may impact these estimates include, but are not limited to, changes in laws and regulations relating to environmental matters, including air and water quality, restoration and abandonment requirements, economic conditions, and supply and demand in the area.
	Management evaluates the ability to recover the carrying amount of its long-lived assets to determine whether its long-lived assets have been impaired. Impairments exist when the carrying amount of an asset exceeds estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. When alternative courses of action to recover the carrying amount of a long-lived asset are under consideration, estimates of future undiscounted cash flows take into account possible outcomes and probabilities of their occurrence. If the carrying amount of the long-lived asset is not recoverable based on the estimated future undiscounted cash flows, the impairment loss is measured as the excess of the asset’s carrying amount over its estimated fair value, such that the asset’s carrying amount is adjusted to its estimated fair value with an offsetting charge to impairment expense. Refer to Note 7 for a description of impairments recorded during the years ended December 31, 2014, 2013 and 2012.
	1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
	Capitalized interest. Interest is capitalized as part of the historical cost of constructing assets for significant projects that are in progress. Capitalized interest is determined by multiplying the Partnership’s weighted-average borrowing cost on debt by the average amount of qualifying costs incurred. Once the construction of an asset subject to interest capitalization is completed and the asset is placed in service, the associated capitalized interest is expensed through depreciation or impairment, together with other capitalized costs related to that asset.
	Goodwill. Goodwill is recorded when the purchase price of a business acquired exceeds the fair market value of the tangible and separately measurable intangible net assets. Refer to Note 8 for a discussion of goodwill. The Partnership evaluates goodwill for impairment annually, as of October 1, or more often as facts and circumstances warrant. The Partnership has allocated goodwill on its two reporting units: (i) gathering and processing and (ii) transportation. An initial qualitative assessment may be performed prior to proceeding to the comparison of the fair value of each reporting unit to which goodwill has been assigned, to the carrying amount of net assets, including goodwill, of each reporting unit. If the Partnership concludes, based on qualitative factors, that it is more likely than not that the fair value of the reporting unit exceeds its carrying amount, then goodwill is not impaired, and estimating the fair value of the reporting unit is not necessary. If the carrying amount of the reporting unit exceeds its fair value, goodwill is written down to its implied fair value through a charge to operating expense based on a hypothetical purchase price allocation. The carrying value of goodwill after such an impairment would represent a Level 3 fair value measurement.
	Other intangible assets. The Partnership assesses intangible assets, as described in Note 8, for impairment together with related underlying long-lived assets whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. See Property, plant and equipment within this Note 1 for further discussion of management’s process to evaluate potential impairment of long-lived assets.
	Asset retirement obligations. Management recognizes a liability based on the estimated costs of retiring tangible long-lived assets. The liability is recognized at fair value, measured using discounted expected future cash outflows for the asset retirement obligation when the obligation originates, which generally is when an asset is acquired or constructed. The carrying amount of the associated asset is increased commensurate with the liability recognized. Over time, the discounted liability is adjusted to its expected settlement value through accretion expense, which is reported within depreciation, amortization and impairments in the consolidated statements of income. Subsequent to the initial recognition, the liability is also adjusted for any changes in the expected value of the retirement obligation (with a corresponding adjustment to property, plant and equipment) until the obligation is settled. Revisions in estimated asset retirement obligations may result from changes in estimated inflation rates, discount rates, asset retirement costs and the estimated timing of settling asset retirement obligations. See Note 11.
	Environmental expenditures. The Partnership expenses environmental obligations related to conditions caused by past operations that do not generate current or future revenues. Environmental obligations related to operations that generate current or future revenues are expensed or capitalized, as appropriate. Liabilities are recorded when the necessity for environmental remediation or other potential environmental liabilities becomes probable and the costs can be reasonably estimated. Accruals for estimated losses from environmental remediation obligations are recognized no later than at the time of the completion of the remediation feasibility study. These accruals are adjusted as additional information becomes available or as circumstances change. Costs of future expenditures for environmental-remediation obligations are not discounted to their present value. See Note 13.
	Segments. The Partnership’s operations are organized into a single operating segment, the assets of which gather, process, compress, treat and transport Anadarko and third-party natural gas, condensate, NGLs and crude oil in the United States.
	1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
	Revenues and cost of product. Under its fee-based gathering, treating and processing arrangements, the Partnership is paid a fixed fee based on the volume and thermal content of natural gas and recognizes revenues for its services in the month such services are performed. Producers’ wells are connected to the Partnership’s gathering systems for delivery of natural gas to the Partnership’s processing or treating plants, where the natural gas is processed to extract NGLs and condensate or treated in order to satisfy pipeline specifications. In some areas, where no processing is required, the producers’ gas is gathered and delivered to pipelines for market delivery. Under cost-of-service gathering agreements, the Partnership earns fees for gathering and compression services based on rates calculated in a cost-of-service model and reviewed periodically over the life of the agreements. Under percent-of-proceeds contracts, revenue is recognized when the natural gas, NGLs or condensate are sold. The percentage of the product sale ultimately paid to the producer is recorded as a related cost of product expense.
	The Partnership purchases natural gas volumes at the wellhead for gathering and processing. As a result, the Partnership has volumes of NGLs and condensate to sell and volumes of residue to either sell, to use for system fuel or to satisfy keep-whole obligations. In addition, depending upon specific contract terms, condensate and NGLs recovered during gathering and processing are either returned to the producer or retained and sold. Under keep-whole contracts, when condensate or NGLs are retained and sold, producers are kept whole for the condensate or NGL volumes through the receipt of a thermally equivalent volume of residue. The keep-whole contract conveys an economic benefit to the Partnership when the combined value of the individual NGLs is greater in the form of liquids than as a component of the natural gas stream; however, the Partnership is adversely impacted when the value of the NGLs is lower than the value of the natural gas stream including the liquids. The Partnership has commodity price swap agreements with Anadarko to mitigate exposure to a substantial majority of the commodity price uncertainty that would otherwise be present as a result of the purchase and sale of natural gas, condensate or NGLs. See Note 5. Revenue is recognized from the sale of condensate and NGLs upon transfer of title and related purchases are recorded as cost of product.
	The Partnership earns transportation revenues through firm contracts that obligate each of its customers to pay a monthly reservation or demand charge regardless of the pipeline capacity used by that customer. An additional commodity usage fee is charged to the customer based on the actual volume of natural gas transported. Transportation revenues are also generated from interruptible contracts pursuant to which a fee is charged to the customer based on volumes transported through the pipeline. Revenues for transportation of natural gas and NGLs are recognized over the period of firm transportation contracts or, in the case of usage fees and interruptible contracts, when the volumes are received into the pipeline. From time to time, certain revenues may be subject to refund pending the outcome of rate matters before the Federal Energy Regulatory Commission (the “FERC”) and reserves are established where appropriate.
	Proceeds from the sale of residue, NGLs and condensate are reported as revenues from natural gas, natural gas liquids and condensate sales in the consolidated statements of income. Revenues attributable to the fixed-fee component of gathering and processing contracts as well as demand charges and commodity usage fees on transportation contracts are reported as revenues from gathering, processing and transportation of natural gas and natural gas liquids in the consolidated statements of income.
	Equity-based compensation. Phantom unit awards are granted under the Western Gas Partners, LP 2008 Long-Term Incentive Plan (the “WES LTIP”). The WES LTIP was adopted by the general partner of the Partnership and permits the issuance of up to 2,250,000 units, of which 2,133,227 units remained available for future issuance as of December 31, 2014. Upon vesting of each phantom unit awarded under the WES LTIP, the holder will receive common units of the Partnership or, at the discretion of the general partner’s Board of Directors, cash in an amount equal to the market value of common units of the Partnership on the vesting date. Equity-based compensation expense attributable to grants made under the WES LTIP impact the Partnership’s cash flows from operating activities only to the extent cash payments are made to a participant in lieu of issuance of common units to the participant. The Partnership amortizes stock-based compensation expense attributable to awards granted under the WES LTIP over the vesting periods applicable to the awards.
	1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
	Additionally, the Partnership’s general and administrative expenses include equity-based compensation costs allocated by Anadarko to the Partnership for grants made pursuant to (i) the Western Gas Equity Partners, LP 2012 Long-Term Incentive Plan (the “WGP LTIP”) for the years ended December 31, 2014 and 2013, (ii) the Western Gas Holdings, LLC Equity Incentive Plan, as amended and restated (the “Incentive Plan”) for the year ended December 31, 2012, and (iii) the Anadarko Petroleum Corporation 1999 Stock Incentive Plan and the Anadarko Petroleum Corporation 2008 and 2012 Omnibus Incentive Compensation Plans (Anadarko’s plans are referred to collectively as the “Anadarko Incentive Plans”) for all periods presented. Grants made under equity-based compensation plans result in equity-based compensation expense, which is determined by reference to the fair value of equity compensation. For equity-based awards ultimately settled through the issuance of units or stock, the fair value is measured as of the date of the relevant equity grant. Equity-based compensation granted under the WGP LTIP and the Anadarko Incentive Plans does not impact the Partnership’s cash flows from operating activities since the offset to compensation expense is recorded as a contribution to partners’ capital in the consolidated financial statements at the time of contribution, when the expense is realized. However, distribution equivalent rights awarded in tandem with equity-or liability-based awards are paid in cash and reflected within financing cash flows in the consolidated statements of cash flows. See Note 5.
	Income taxes. The Partnership generally is not subject to federal income tax or state income tax other than Texas margin tax on the portion of its income that is apportionable to Texas. Deferred state income taxes are recorded on temporary differences between the financial statement carrying amounts of assets and liabilities and their respective tax bases. The Partnership routinely assesses the realizability of its deferred tax assets. If the Partnership concludes that it is more likely than not that some of the deferred tax assets will not be realized, the tax asset is reduced by a valuation allowance. Federal and state current and deferred income tax expense was recorded on the Partnership assets prior to the Partnership’s acquisition of these assets from Anadarko.
	For periods beginning on and subsequent to the Partnership’s acquisition of the Partnership assets, the Partnership makes payments to Anadarko pursuant to the tax sharing agreement entered into between Anadarko and the Partnership for its estimated share of taxes from all forms of taxation, excluding taxes imposed by the United States, that are included in any combined or consolidated returns filed by Anadarko. The aggregate difference in the basis of the Partnership’s assets for financial and tax reporting purposes cannot be readily determined as the Partnership does not have access to information about each partner’s tax attributes in the Partnership.
	The accounting standards for uncertain tax positions defines the criteria an individual tax position must satisfy for any part of the benefit of that position to be recognized in the financial statements. The Partnership had no material uncertain tax positions at December 31, 2014 or 2013.
	With respect to assets acquired from Anadarko, the Partnership recorded Anadarko’s historic current and deferred income taxes for the periods prior to the Partnership’s ownership of the assets. For periods subsequent to the Partnership’s acquisition, the Partnership is not subject to tax except for the Texas margin tax and, accordingly, does not record current and deferred federal income taxes related to the assets acquired from Anadarko.
	Net income per common unit. The Partnership applies the two-class method in determining net income per unit applicable to master limited partnerships having multiple classes of securities including common units, Class C units, general partner units and IDRs. The two-class method is an earnings allocation formula that treats participating securities as having rights to earnings that otherwise would have been available to common unitholders. Under the two-class method, net income per unit is calculated as if all of the earnings for the period were distributed pursuant to the terms of the relevant contractual arrangement. The accounting guidance provides the methodology for and circumstances under which undistributed earnings are allocated to the general partner, limited partners and IDR holders. For the Partnership, earnings per unit is calculated based on the assumption that the Partnership distributes to its unitholders an amount of cash equal to the net income of the Partnership, notwithstanding the general partner’s ultimate discretion over the amount of cash to be distributed for the period, the existence of other legal or contractual limitations that would prevent distributions of all of the net income for the period or any other economic or practical limitation on the ability to make a full distribution of all of the net income for the period.
	1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
	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 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 (see discussion of Class C beneficial conversion feature and related impacts on earnings per unit in Note 4). Specifically, net income equal to the amount of available cash (as defined by the partnership agreement) is allocated to the general partner, common and Class C unitholders consistent with actual cash distributions and capital account allocations, including incentive distributions allocable to the general partner. Undistributed earnings (net income in excess of distributions) or undistributed losses (available cash in excess of net income) are then allocated to the general partner, common unitholders and Class C unitholders in accordance with their respective weighted-average ownership percentages during each period. 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 and Class C unit. See Note 4.
	Contributions in aid of construction costs from affiliates. On certain of the Partnership’s capital projects, Anadarko is obligated to reimburse the Partnership for all or a portion of project capital expenditures. The majority of such arrangements are associated with projects related to pipeline construction activities and production well tie-ins. These cash receipts are presented as “Contributions in aid of construction costs from affiliates” within the investing section of the Partnership’s consolidated statements of cash flows. See Note 5.
	Recently issued accounting standards. Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers, 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 to which the entity expects to be entitled 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 currently evaluating the impact of the adoption of this ASU on its consolidated financial statements.
	ASU 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, changes the criteria for reporting discontinued operations and requires additional disclosures, both for discontinued operations and for individually significant dispositions and assets classified as held for sale not qualifying as discontinued operations. This ASU is effective for annual and interim periods beginning in 2015, with early adoption permitted for disposals or for assets classified as held for sale that have not been reported in previously issued financial statements. The Partnership early adopted this ASU on a prospective basis beginning with the first quarter of 2014. The adoption did not have a material impact on the Partnership’s consolidated financial statements.
ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists, requires that an unrecognized tax benefit, or a portion of an unrecognized tax benefit, be presented in the financial statements as a reduction to a deferred tax asset, except in certain circumstances. This ASU is effective for annual and interim periods beginning in 2014. The Partnership adopted this ASU on a prospective basis beginning with the first quarter of 2014. The adoption did not have a material impact on the Partnership’s consolidated financial statements. See Note 6—Income Taxes.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Acquisitions	2.  ACQUISITIONS
	In May 2008, concurrently with the closing of the Partnership’s IPO, Anadarko contributed to the Partnership the assets and liabilities of Anadarko Gathering Company LLC, Pinnacle Gas Treating LLC, and MIGC LLC. In December 2008, the Partnership completed the acquisition of the Powder River assets from Anadarko, which included (i) the Hilight system, (ii) a 50% interest in the Newcastle system and (iii) a 14.81% membership interest in Fort Union. In July 2009, the Partnership closed on the acquisition of a 51% membership interest in Chipeta from Anadarko. The Partnership closed the acquisitions of Anadarko’s Granger and Wattenberg assets in January 2010 and August 2010, respectively. In September 2010, the Partnership acquired a 10% interest in White Cliffs. The Partnership closed the acquisition of the Platte Valley assets from a third party in February 2011 and the acquisition of the Bison assets from Anadarko in July 2011.
	The following table presents the acquisitions completed by the Partnership during the years ended December 31, 2014, 2013 and 2012, and identifies the funding sources for such acquisitions:
	thousands except unit and percent amounts		Acquisition		Percentage			Borrowings		Cash		Common	Class C	GP Units
			Date		Acquired					On Hand		Units Issued to Anadarko	Units Issued to Anadarko	Issued
	MGR (1)		1/13/12		100	%		$	299,000	$	159,587	632,783	—	12,914
	Chipeta (2)		8/1/12		24	%		—		128,250		151,235	—	3,086
	Non-Operated Marcellus Interest (3)		3/1/13		33.75	%		250,000		215,500		449,129	—	—
	Anadarko-Operated Marcellus Interest (4)		3/8/13		33.75	%		133,500		—		—	—	—
	Mont Belvieu JV (5)		6/5/13		25	%		—		78,129		—	—	—
	OTTCO (6)		9/3/13		100	%		27,500		—		—	—	—
	TEFR Interests (7)		3/3/14		Various (7)			350,000		6,250		308,490	—	—
	DBM (8)		11/25/14		100	%		475,000		298,327		—	10,913,853	—
	(1)	The assets acquired from Anadarko consisted of (i) the “Red Desert complex,” which is located in the greater Green River Basin in southwestern Wyoming, and includes the Patrick Draw processing plant, the Red Desert processing plant, gathering lines, and related facilities, (ii) a 22% interest in Rendezvous, which owns a gathering system serving the Jonah and Pinedale Anticline fields in southwestern Wyoming, and (iii) certain additional midstream assets and equipment. These assets are collectively referred to as the “MGR assets” and the acquisition as the “MGR acquisition.”
	(2)	The Partnership acquired Anadarko’s additional Chipeta interest (as described in Note 1). The Partnership received distributions related to the additional interest beginning July 1, 2012. This transaction brought the Partnership’s total membership interest in Chipeta to 75%. The remaining 25% membership interest in Chipeta held by a third-party member is reflected as noncontrolling interests in the consolidated financial statements for all periods presented.
	(3)	The Partnership acquired Anadarko’s 33.75% interest (non-operated) (the “Non-Operated Marcellus Interest”) in the Liberty and Rome gas gathering systems (the “Non-Operated Marcellus Interest systems”), serving production from the Marcellus shale in North-central Pennsylvania. In connection with the issuance of the common units, the Partnership’s general partner purchased 9,166 general partner units for consideration of $0.5 million.
	(4)	The Partnership acquired a 33.75% interest (the “Anadarko-Operated Marcellus Interest”) in each of the Larry’s Creek, Seely and Warrensville gas gathering systems (the “Anadarko-Operated Marcellus Interest systems”), which are operated by Anadarko and serve production from the Marcellus shale in North-central Pennsylvania, from a third party. During the third quarter of 2013, the Partnership recorded a $1.1 million decrease in the assets acquired and liabilities assumed in the acquisition, representing the final purchase price allocation.
	(5)	The Partnership acquired a 25% interest in the Mont Belvieu JV, an entity formed to design, construct, and own two fractionation trains located in Mont Belvieu, Texas, from a third party. The interest acquired is accounted for under the equity method of accounting.
	(6)	The Partnership acquired Overland Trail Transmission, LLC (“OTTCO”), a Delaware limited liability company, from a third party. OTTCO owns and operates an intrastate pipeline that connects the Partnership’s Red Desert and Granger complexes in southwestern Wyoming.
	(7)	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.
	(8)	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 serve production from Reeves, Loving and Culberson Counties, Texas and Eddy and Lea Counties, New Mexico. These assets are referred to collectively as the “DBM complex.” See Note 4 for a discussion of the Class C units.
	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 to the assets acquired and liabilities assumed in the DBM acquisition as of the acquisition date, pending the acquired entity’s final financial statements:
	thousands
	Current assets		$	46,358
	Property, plant and equipment		440,971
	Goodwill		279,051
	Other intangible assets		835,566
	Accounts payables		(13,064		)
	Accrued liabilities		(24,824		)
	Deferred income taxes		(1,450		)
	Asset retirement obligations and other		(8,649		)
	Total purchase price		$	1,553,959
	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.
	The following table presents pro forma condensed financial information of the Partnership as if the DBM acquisition had occurred on January 1, 2013:
			Year Ended December 31,
	thousands except per-unit amounts		2014				2013
	Revenues		$	1,397,030			$	1,107,030
	Net income		332,420				239,382
	Net income attributable to Western Gas Partners, LP		318,395				228,566
	Net income per common unit – basic and diluted		1.34				1.12
	The pro forma information is presented for illustration purposes only and is not necessarily indicative of the operating results that would have occurred had the DBM acquisition been completed at the assumed date, nor is it necessarily indicative of future operating results of the combined entity. The Partnership’s pro forma information in the table above includes $12.5 million of revenues and $10.4 million of operating expenses, excluding depreciation, amortization and impairments, attributable to the DBM complex that are included in the Partnership’s consolidated statement of income for the year ended December 31, 2014. The pro forma adjustments reflect pre-acquisition results of the DBM acquisition including (a) revenues and expenses; (b) depreciation and amortization based on the purchase price allocated to property, plant and equipment and estimated useful lives; (c) amortization of intangible assets (customer contracts assumed in the acquisition); and (d) interest on borrowings under the Partnership’s senior unsecured revolving credit facility (“RCF”) to finance the DBM acquisition. The pro forma adjustments include estimates and assumptions based on currently available information. Management believes the estimates and assumptions are reasonable, and the relative effects of the transaction are properly reflected. The pro forma information does not reflect any cost savings or other synergies anticipated as a result of the DBM acquisition, nor any future acquisition related expenses.

Partnership_Distributions

Partnership Distributions	12 Months Ended
	Dec. 31, 2014
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
	2012
	31-Mar			$	0.46		$	46,053	May-12
	30-Jun			0.48			52,425		August 2012
	30-Sep			0.5			56,346		Nov-12
	31-Dec			0.52			65,657		Feb-13
	2013
	31-Mar			$	0.54		$	70,143	May 2013
	30-Jun			0.56			79,315		Aug-13
	30-Sep			0.58			83,986		Nov-13
	31-Dec			0.6			92,609		Feb-14
	2014
	31-Mar			$	0.625		$	98,749	May 2014
	30-Jun			0.65			105,655		Aug-14
	30-Sep			0.675			111,608		Nov-14
	December 31 (1)			0.7			126,044		Feb-15
	(1)	On January 22, 2015, the Board of Directors of the Partnership’s general partner declared a cash distribution to the Partnership’s unitholders of $0.700 per unit, or $126.0 million in aggregate, including incentive distributions, but excluding distributions on Class C units (see Class C unit distributions below). The cash distribution was paid on February 12, 2015, to unitholders of record at the close of business on February 2, 2015.
	Available cash. The amount of available cash (as defined in the partnership agreement) generally is all cash on hand at the end of the quarter, plus, at the discretion of the general partner, working capital borrowings made subsequent to the end of such quarter, less the amount of cash reserves established by the Partnership’s general partner to provide for the proper conduct of the Partnership’s business, including reserves to fund future capital expenditures; to comply with applicable laws, debt instruments or other agreements; or to provide funds for distributions to its unitholders, and to its general partner for any one or more of the next four quarters. Working capital borrowings generally include borrowings made under a credit facility or similar financing arrangement. It is intended that working capital borrowings be repaid within 12 months. In all cases, working capital borrowings are used solely for working capital purposes or to fund distributions to partners.
	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 C units”) until the end of 2017 (unless earlier converted, see Note 4), 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 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 C distributions at fair value at the time of issuance. This fair value measurement uses the Partnership’s unit price as a significant input in the determination of the fair value and thus represents a Level 2 measurement. On February 12, 2015, the Partnership’s general partner distributed 45,711 PIK C units to the Class C unitholder, based on the $0.700 common unit distribution referenced above, 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.
	General partner interest and incentive distribution rights. As of December 31, 2014, the general partner was entitled to 1.9% of all quarterly distributions that the Partnership makes prior to its liquidation (see Note 4). The Partnership’s general partner, as the holder of the IDRs, was entitled to incentive distributions at the maximum distribution sharing percentage of 48.0% for all periods presented.
			Total Quarterly Distribution		Marginal Percentage
			Target Amount		Interest in Distributions
					Unitholders	General Partner
	Minimum quarterly distribution		$0.30		98.10%	1.90%
	First target distribution		up to $0.345		98.10%	1.90%
	Second target distribution		above $0.345 up to $0.375		85.10%	14.90%
	Third target distribution		above $0.375 up to $0.450		75.10%	24.90%
	Thereafter		above $0.450		50.10%	49.90%
	The maximum distribution sharing percentage of 49.9% includes distributions paid to the general partner on its 1.9% general partner interest and the 48.0% IDR maximum distribution sharing percentage, and does not include any distributions that the general partner may receive on common units that it may acquire.

Equity_and_Partners_Capital

Equity and Partners' Capital	12 Months Ended
	Dec. 31, 2014
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 2014, 2013 and 2012:
	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
	June 2012 equity offering	5,000,000			102,041			$	43.88			$	7,468	$	216,409
	May 2013 equity offering (2)	7,015,000			143,163			61.18				13,203		424,733
	December 2013 equity offering (3)	4,800,000			97,959			61.51				9,447		291,827
	Continuous Offering Program - 2013 (4)	685,735			13,996			60.84				965		41,603
	Continuous Offering Program - 2014 (5)	1,133,384			23,132			73.48				1,738		83,245
	November 2014 equity offering (6)	8,620,153			153,061			70.85				18,583		602,999
	(1)	Represents general partner units issued to the general partner in exchange for the general partner’s proportionate capital contribution.
	(2)	Includes the issuance of 915,000 common units pursuant to the full exercise of the underwriters’ over-allotment option.
	(3)	Includes the issuance of 300,000 common units on January 3, 2014, pursuant to the partial exercise of the underwriters’ over-allotment option. Net proceeds from this partial exercise (including the general partner’s proportionate capital contribution) were $18.1 million.
	(4)	Represents common and general partner units issued during the year ended December 31, 2013, pursuant to the Partnership’s registration statement filed with the U.S. Securities and Exchange Commission (“SEC”) in August 2012 authorizing the issuance of up to an aggregate of $125.0 million of common units (the “Continuous Offering Program”). Gross proceeds generated (including the general partner’s proportionate capital contributions) during the year ended December 31, 2013, were $42.6 million. The price per unit in the table above represents an average price for all issuances under the Continuous Offering Program during 2013.
	(5)	Represents common and general partner units issued during the year ended December 31, 2014, under the Continuous Offering Program. 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 Continuous Offering Program 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.
	(6)	Includes the issuance of 1,120,153 common units pursuant to the partial exercise of the underwriters’ over-allotment option. Net proceeds from this partial exercise were $77.0 million. Beginning with this partial exercise, the Partnership’s general partner elected not to make a corresponding capital contribution to maintain the general partner’s 2.0% interest in the Partnership. See Note 3.
	Common and general partner units. The Partnership’s common units are listed on the New York Stock Exchange under the symbol “WES.”
	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 APC Midstream Holdings, LLC (“AMH”), a subsidiary of Anadarko, 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 if the Partnership were to receive cash proceeds from an entity that is not an affiliate of the Partnership or AMH, and 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, then the Partnership would be able to redeem up to $150.0 million of the Class C units within 10 days of the receipt of such proceeds. As of December 31, 2014, no Class C units had been redeemed.
	4.  EQUITY AND PARTNERS’ CAPITAL (CONTINUED)
	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 is 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 will amortize the beneficial conversion feature assuming a conversion date of December 31, 2017, using the effective yield method. The impact of the beneficial conversion feature will also be included in the calculation of earnings per unit.
	The following table summarizes the common, Class C and general partner units issued during the years ended December 31, 2014 and 2013:
			Common			Class C Units			General			Total
			Units						Partner Units
	Balance at December 31, 2012		104,660,553			—			2,135,930			106,796,483
	Non-Operated Marcellus Interest acquisition		449,129			—			9,166			458,295
	Long-Term Incentive Plan awards		12,395			—			253			12,648
	May 2013 equity offering		7,015,000			—			143,163			7,158,163
	Continuous Offering Program		685,735			—			13,996			699,731
	December 2013 equity offering		4,500,000			—			91,837			4,591,837
	Balance at December 31, 2013		117,322,812			—			2,394,345			119,717,157
	December 2013 equity offering		300,000			—			6,122			306,122
	Long-Term Incentive Plan awards		10,291			—			112			10,403
	TEFR Interests acquisition		308,490			—			6,296			314,786
	Continuous Offering Program		1,133,384			—			23,132			1,156,516
	November 2014 equity offering		8,620,153			—			153,061			8,773,214
	Class C unit issuance		—			10,913,853			—			10,913,853
	Balance at December 31, 2014		127,695,130			10,913,853			2,583,068			141,192,051
	Holdings of Partnership equity. As of December 31, 2014, WGP held 49,296,205 common units, representing a 34.9% 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 December 31, 2014, other subsidiaries of Anadarko held 757,619 common units and 10,913,853 Class C units, representing an aggregate 8.3% limited partner interest in the Partnership. As of December 31, 2014, the public held 77,641,306 common units, representing a 55.0% limited partner interest in the Partnership.
	The Partnership’s net income earned on and subsequent to the date of the acquisition of the Partnership assets (as defined in Note 1) is allocated to the general partner and the limited partners consistent with actual cash distributions, including incentive distributions allocable to the general partner. Undistributed earnings (net income in excess of distributions) or undistributed losses (available cash in excess of net income) are then allocated to the general partner and the limited partners in accordance with their respective ownership percentages.
	4.  EQUITY AND PARTNERS’ CAPITAL (CONTINUED)
	Net income per unit for common units. 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:
		Year Ended December 31,
	thousands except per-unit amounts	2014				2013				2012
	Net income attributable to Western Gas Partners, LP	$	376,533			$	274,627			$	134,377
	Pre-acquisition net (income) loss allocated to Anadarko	956				(4,128		)		(27,391		)
	General partner interest in net (income) loss	(120,980		)		(69,633		)		(28,089		)
	Limited partners’ interest in net income	256,509				200,866				78,897
	Net income allocable to common units	254,737				200,866				78,897
	Net income allocable to Class C units	1,772				—				—
	Limited partners’ interest in net income	$	256,509			$	200,866			$	78,897
	Net income per unit
	Common units - basic	$	2.13			$	1.83			$	0.84
	Common units – diluted	2.12				1.83				0.84
	Weighted-average units outstanding
	Common units – basic	119,822				109,872				93,936
	Class C units	1,106				—				—
	Common units – diluted	120,928				109,872				93,936

Transactions_With_Affiliates

Transactions With Affiliates	12 Months Ended
	Dec. 31, 2014
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, 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 1 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. Anadarko charged or credited the Partnership interest at a variable rate on outstanding affiliate balances for the periods these balances remained outstanding. 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, and affiliate-based interest expense on current intercompany balances is not charged. 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 amount payable to Anadarko. Concurrently with the closing of the Partnership’s May 2008 IPO, 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 $317.8 million and $296.7 million at December 31, 2014 and 2013, 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.
	In 2008, the Partnership entered into a five-year $175.0 million term loan agreement with Anadarko, which was repaid in full in June 2012 using the proceeds from the issuance of 4.000% Senior Notes due 2022. See Note 12.
	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 and at the DJ Basin and Red Desert complexes, 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 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 December 31, 2014:
	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:
			Year Ended December 31,
	thousands		2014				2013				2012
	Gains (losses) on commodity price swap agreements related to sales: (1)
	Natural gas sales		$	9,494			$	21,382			$	37,665
	Natural gas liquids sales		113,866				102,076				66,260
	Total		123,360				123,458				103,925
	Losses on commodity price swap agreements related to purchases (2)		(68,492		)		(85,294		)		(89,710		)
	Net gains (losses) on commodity price swap agreements		$	54,868			$	38,164			$	14,215
	(1)	Reported in affiliate natural gas, natural gas liquids and 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%, 54% and 62% for the years ended December 31, 2014, 2013 and 2012, 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 57%, 59% and 61% for the years ended December 31, 2014, 2013 and 2012, respectively. Throughput percentages are not directly comparable because the formation of the DJ Basin complex resulted in the following: (i) the Wattenberg system volumes previously reported as “Gathering, treating and transportation” are now reported as “Processing” for all periods presented, and (ii) beginning in 2014, volumes both gathered and processed by the two systems are no longer separately reported.
	Gas purchase and sale agreements. The Partnership sells substantially all of its natural gas, condensate and NGLs to Anadarko Energy Services Company (“AESC”), Anadarko’s marketing affiliate. In addition, the Partnership purchases natural gas from AESC pursuant to gas purchase agreements. The Partnership’s gas purchase and sale agreements with AESC are generally one-year contracts, subject to annual renewal.
	Omnibus agreement. Pursuant to the omnibus agreement, Anadarko performs centralized corporate functions for the Partnership, such as legal; accounting; treasury; cash management; investor relations; insurance administration and claims processing; risk management; health, safety and environmental; information technology; human resources; credit; payroll; internal audit; tax; marketing; and midstream administration. Anadarko, in accordance with the partnership and omnibus agreements, determines, in its reasonable discretion, amounts to be reimbursed by the Partnership in exchange for services provided under the omnibus agreement. See Summary of affiliate transactions below.
	The following table summarizes the amounts the Partnership reimbursed to Anadarko:
			Year Ended December 31,
	thousands		2014				2013				2012
	General and administrative expenses		$	20,249			$	16,882			$	14,904
	Public company expenses		8,006				7,152				6,830
	Total reimbursement		$	28,255			$	24,034			$	21,734
	5.  TRANSACTIONS WITH AFFILIATES (CONTINUED)
	Services and secondment agreement. Pursuant to the services and secondment agreement, specified employees of Anadarko are seconded to the general partner to provide operating, routine maintenance and other services with respect to the assets owned and operated by the Partnership under the direction, supervision and control of the general partner. Pursuant to the services and secondment agreement, the Partnership reimburses Anadarko for services provided by the seconded employees. The initial term of the services and secondment agreement extends through May 2018 and the term will automatically extend for additional twelve-month periods unless either party provides 180 days written notice of termination before the applicable twelve-month period expires. The consolidated financial statements include costs allocated by Anadarko for expenses incurred under the services and secondment agreement for periods including and subsequent to the Partnership’s acquisition of the Partnership assets.
	Tax sharing agreement. Pursuant to a tax sharing agreement, the Partnership reimburses Anadarko for its estimated share of applicable state taxes. These taxes include income taxes attributable to the Partnership’s income which are directly borne by Anadarko through its filing of a combined or consolidated tax return with respect to periods beginning on and subsequent to the acquisition of the Partnership assets from Anadarko. Anadarko may use its own tax attributes to reduce or eliminate the tax liability of its combined or consolidated group, which may include the Partnership as a member. However, under this circumstance, the Partnership nevertheless is required to reimburse Anadarko for its allocable share of taxes that would have been owed had tax attributes not been available to Anadarko.
	Allocation of costs. For periods prior to the Partnership’s acquisition of the Partnership assets, the consolidated financial statements include costs allocated by Anadarko in the form of a management services fee, which approximated the general and administrative costs incurred by Anadarko attributable to the Partnership assets. This management services fee was allocated to the Partnership based on its proportionate share of Anadarko’s assets and revenues or other contractual arrangements. Management believes these allocation methodologies are reasonable.
	The employees supporting the Partnership’s operations are employees of Anadarko. Anadarko allocates costs to the Partnership for its share of personnel costs, including costs associated with equity-based compensation plans, non-contributory defined pension and postretirement plans, defined contribution savings plan pursuant to the omnibus agreement and services and secondment agreement. In general, the Partnership’s reimbursement to Anadarko under the omnibus agreement or services and secondment agreements is either (i) on an actual basis for direct expenses Anadarko and the general partner incur on behalf of the Partnership, or (ii) based on an allocation of salaries and related employee benefits between the Partnership, the general partner and Anadarko based on estimates of time spent on each entity’s business and affairs. Most general and administrative expenses charged to the Partnership by Anadarko are attributed to the Partnership on an actual basis, and do not include any mark-up or subsidy component. With respect to allocated costs, management believes the allocation method employed by Anadarko is reasonable. Although it is not practicable to determine what the amount of these direct and allocated costs would be if the Partnership were to directly obtain these services, management believes that aggregate costs charged to the Partnership by Anadarko are reasonable.
	5.  TRANSACTIONS WITH AFFILIATES (CONTINUED)
	WES LTIP. The general partner awards phantom units under the WES LTIP primarily to its independent directors and its Chief Executive Officer. 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 $0.6 million for each of the years ended December 31, 2014 and 2013, and $0.4 million for the year ended December 31, 2012. As of December 31, 2014, there was $0.3 million of unrecognized compensation expense attributable to the outstanding awards under the WES LTIP, of which $0.2 million will be realized by the Partnership, and which is expected to be recognized over a weighted-average period of 0.7 years.
	The following table summarizes WES LTIP award activity for the years ended December 31, 2014, 2013 and 2012:
		2014							2013							2012
		Weighted-Average Grant-Date Fair Value				Units			Weighted-Average Grant-Date Fair Value				Units			Weighted-Average Grant-Date Fair Value			Units
	Phantom units outstanding at beginning of year	$	49.47			16,844			$	41.77			25,619			$	33.92		23,978
	Vested	49.55				(13,122	)		41.28				(14,695	)		33.2			(14,260	)
	Granted	68.14				5,800			62.49				5,920			45.91			15,901
	Phantom units outstanding at end of year	60.74				9,522			49.47				16,844			41.77			25,619
	WGP LTIP and Anadarko Incentive Plans. For the years ended December 31, 2014, 2013 and 2012, general and administrative expenses included $3.5 million, $3.0 million and $3.3 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 WGP LTIP and Anadarko Incentive Plans. Of these amounts, $3.2 million, $2.9 million and $3.2 million for the years ended December 31, 2014, 2013 and 2012, respectively, of allocated equity-based compensation expense is reflected as a contribution to partners’ capital in the Partnership’s consolidated statements of equity and partners’ capital. As of December 31, 2014, the Partnership estimated that $7.2 million of unrecognized compensation expense attributable to the WGP LTIP and the Anadarko Incentive Plans will be allocated to the Partnership over a weighted-average period of 2.1 years.
	The Incentive Plan. For the year ended December 31, 2012, the Partnership’s general and administrative expenses included $68.8 million of compensation expense for grants of Unit Value Rights (“UVRs”), Unit Appreciation Rights (“UARs”) and Distribution Equivalent Rights (“DERs”) under the Incentive Plan to certain executive officers of the general partner as a component of their compensation, which was allocated to the Partnership by Anadarko.
	Under the terms of the Incentive Plan, the value of a UAR was equal to an amount calculated by dividing the “determined value” (defined below) by 1,000,000, less the applicable UAR exercise price. Prior to WGP’s IPO in December 2012, the value of awards issued under the Incentive Plan were revised periodically based on the estimated fair value of the Partnership’s general partner using a discounted cash flow estimate and multiples-valuation terminal value.
	5.  TRANSACTIONS WITH AFFILIATES (CONTINUED)
	Anadarko and the Incentive Plan participants entered into a Memorandum of Understanding (the “MOU”) that, among other things, confirmed the intent and the understanding that the WGP IPO resulted in the vesting of all unvested Incentive Plan awards and that the value of the Partnership’s common units held by WGP prior to its IPO would not be considered in the valuation of the Incentive Plan awards.
	The WGP IPO and concurrent execution of the MOU triggered the exercise of all outstanding UARs and lump-sum cash payments (less any applicable withholding taxes) to plan participants equal to the value of each award, less its exercise price, if applicable. Pursuant to the MOU, the “determined value” was defined as equal to the aggregate WGP equity value, as determined using the market price of WGP based on the IPO price of WGP’s common units, reduced by the market value of the Partnership’s common units owned by WGP prior to its IPO (based on the closing price of the Partnership’s common units on the day of the pricing of the IPO). Awards outstanding under the Incentive Plan at the time of the WGP IPO (and the effective termination of the Incentive Plan) were valued at $2,745.00 per UAR and $12.00 per DER. Outstanding UVRs that vested concurrent with the WGP IPO were cash-settled at their grant-date fair value.
	In addition to the execution of the MOU, WGP, the Partnership’s general partner and Anadarko entered into a contribution agreement whereby cash, in an amount equal to the aggregate cash payment required to settle all outstanding awards, was contributed to the Partnership’s general partner by Anadarko. The cash payments made in connection with WGP’s IPO and the vesting, exercise and settlement of all outstanding awards under the Incentive Plan as described above, impacted the Partnership’s cash flows to the extent compensation expense was allocated to the Partnership since the inception of the Incentive Plan. The compensation expense allocated to the Partnership since the inception of the Incentive Plan, and subsequently contributed by Anadarko during the fourth quarter of 2012, was recorded to partners’ capital in the consolidated financial statements.
	Equipment purchases and sales. The following table summarizes the Partnership’s purchases from and sales to Anadarko of pipe and equipment:
			Year Ended December 31,
			2014				2013				2012				2014			2013			2012
	thousands		Purchases												Sales
	Cash consideration		$	22,943			$	11,211			$	24,705			$	—		$	85		$	760
	Net carrying value		12,210				5,309				8,009				—			38			393
Partners’ capital adjustment		$	10,733			$	5,902			$	16,696			$	—		$	47		$	367
Contributions in aid of construction costs from affiliates. In 2013, a subsidiary of Anadarko entered into an aid in construction agreement with the Partnership, whereby the Partnership constructed five receipt-point facilities at the Brasada complex that serve the Anadarko subsidiary. Such subsidiary reimbursed the Partnership for costs associated with construction of the receipt points. These reimbursements are presented within the investing section of the Partnership’s consolidated statements of cash flows as “Contributions in aid of construction costs from affiliates.”
5.  TRANSACTIONS WITH AFFILIATES (CONTINUED)
Summary of affiliate transactions. The following table summarizes affiliate transactions, which include revenue from affiliates, reimbursement of operating expenses and purchases of natural gas:
		Year ended December 31,
thousands		2014				2013				2012
Revenues (1)		$	969,995			$	805,526			$	688,026
Equity income, net (1)		57,836				22,948				16,042
Cost of product (1)		114,000				129,045				145,250
Operation and maintenance (2)		58,884				56,435				51,237
General and administrative (3)		26,989				23,354				92,847
Operating expenses		199,873				208,834				289,334
Interest income (4)		16,900				16,900				16,900
Interest expense (5)		—				—				2,766
Distributions to unitholders (6)		234,024				169,150				98,280
Contributions from noncontrolling interest owners (7)		—				—				12,588
Distributions to noncontrolling interest owners (7)		—				—				6,528
(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, WGP LTIP and Anadarko Incentive Plans, and The Incentive Plan within this Note 5).
(4)	Represents interest income recognized on the note receivable from Anadarko.
(5)	For the year ended December 31, 2012, includes interest expense recognized on the note payable to Anadarko (see Note 12) and interest imputed on the reimbursement payable to Anadarko for certain expenditures Anadarko incurred in 2011 related to the construction of the Brasada complex and Lancaster plant. The Partnership repaid the note payable to Anadarko in June 2012, and repaid the reimbursement payable to Anadarko associated with the construction of the Brasada complex and Lancaster plant in the fourth quarter of 2012.
(6)	Represents distributions paid under the partnership agreement (see Note 3 and Note 4).
(7)	As described in Note 2, the Partnership acquired the additional Chipeta interest on August 1, 2012, and accounted for the acquisition on a prospective basis. As such, contributions from noncontrolling interest owners and distributions to noncontrolling interest owners subsequent to the acquisition date no longer reflect contributions from or distributions to Anadarko.
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.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	6.  INCOME TAXES
	The components of the Partnership’s income tax expense (benefit) are as follows:
		Year Ended December 31,
	thousands	2014			2013			2012
	Current income tax expense (benefit)
	Federal income tax expense (benefit)	$	(625	)	$	(30,176	)	$	(7,576	)
	State income tax expense (benefit)	69			640			(1,843		)
	Total current income tax expense (benefit)	(556		)	(29,536		)	(9,419		)
	Deferred income tax expense (benefit)
	Federal income tax expense (benefit)	171			32,930			22,324
	State income tax expense (benefit)	2,412			(1,039		)	7,785
	Total deferred income tax expense (benefit)	2,583			31,891			30,109
	Total income tax expense	$	2,027		$	2,355		$	20,690
	Total income taxes differed from the amounts computed by applying the statutory income tax rate to income before income taxes. The sources of these differences are as follows:
		Year Ended December 31,
	thousands except percentages	2014			2013			2012
	Income before income taxes	$	392,585		$	287,798		$	169,957
	Statutory tax rate	—		%	—		%	—		%
	Tax computed at statutory rate	$	—		$	—		$	—
	Adjustments resulting from:
	Federal taxes on income attributable to Partnership assets pre-acquisition	(454		)	3,090			17,226
	State taxes on income attributable to Partnership assets pre-acquisition (net of federal benefit)	—			624			2,206
	Texas margin tax expense (benefit)	2,481			(1,359		)	1,258
	Income tax expense	$	2,027		$	2,355		$	20,690
	Effective tax rate	1		%	1		%	12		%
	The tax effects of temporary differences that give rise to significant portions of deferred tax assets (liabilities) are as follows:
		December 31,
	thousands	2014			2013
	Credit carryforwards	$	14		$	14
	Net current deferred income tax assets	14			14
	Depreciable property	(3,240		)	(38,528		)
	Credit carryforwards	512			527
	Other intangible assets	(1,450		)	—
	Other	7			3
	Net long-term deferred income tax liabilities	(4,171		)	(37,998		)
	Total net deferred income tax liabilities	$	(4,157	)	$	(37,984	)
	Credit carryforwards, which are available for use on future income tax returns, consist of $0.5 million of state income tax credits that expire in 2026.

Property_Plant_and_Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	7.  PROPERTY, PLANT AND EQUIPMENT
	A summary of the historical cost of the Partnership’s property, plant and equipment is as follows:
			December 31,
	thousands	Estimated Useful Life	2014		2013
	Land	n/a	$	2,839	$	2,584
	Gathering systems	3 to 47 years	4,790,974		3,673,008
	Pipelines and equipment	15 to 45 years	151,107		146,008
	Assets under construction	n/a	464,507		405,633
	Other	3 to 40 years	15,272		11,867
	Total property, plant and equipment		5,424,699		4,239,100
	Accumulated depreciation		1,040,328		855,845
	Net property, plant and equipment		$	4,384,371	$	3,383,255
	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.
	At December 31, 2013, other long-term assets includes $4.6 million of unguaranteed residual value related to the capital lease component of a processing agreement assumed in connection with the acquisition of the Granger straddle plant as a part of the MGR acquisition in January 2012. This agreement, in which the Partnership was the lessor, was replaced effective April 1, 2014, with a gas conditioning agreement that does not satisfy criteria required for lease classification. As such, during the second quarter of 2014, the Partnership reclassified the $4.6 million capital lease asset from other long-term assets to property, plant and equipment and commenced depreciation.
	During 2014, the Partnership recognized impairments of $3.1 million, primarily related to a non-operational plant in the Powder River Basin that was impaired to its estimated fair value of $2.4 million, using Level 3 fair-value inputs, the cancellation of various capital projects by the third-party operator of the Non-Operated Marcellus Interest systems and a compressor no longer in service at the Hilight system.
	During 2013, the Partnership recognized a $1.2 million impairment primarily related to the cancellation of various capital projects by the third-party operator of the Non-Operated Marcellus Interest systems.
	During 2012, the Partnership recognized a $6.0 million impairment related to a gathering system in central Wyoming that was impaired to its estimated fair value using Level 3 fair-value inputs and an impairment of $0.6 million for the original installation costs on a compressor relocated within the Partnership’s operating assets.

Goodwill_and_Intangibles

Goodwill and Intangibles	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangibles	8.  GOODWILL AND INTANGIBLES
	Goodwill. Goodwill is recorded when the purchase price of a business acquired exceeds the fair market value of the tangible and separately measurable intangible net assets. In addition, goodwill represents the allocated portion of Anadarko’s midstream goodwill attributed to the Partnership assets acquired from Anadarko. The carrying value of Anadarko’s midstream goodwill represents the excess of the purchase price paid to a third-party entity over the estimated fair value of the identifiable assets acquired and liabilities assumed by Anadarko. Accordingly, the Partnership’s allocated goodwill balance does not represent, and in some cases is significantly different from, the difference between the consideration the Partnership paid for its acquisitions from Anadarko and the fair value of such net assets on their respective acquisition dates.
	The consolidated balance sheets as of December 31, 2014 and 2013, include goodwill of $384.4 million and $105.3 million, respectively, the impairment of which (if applicable) is not deductible for tax purposes. The Partnership recorded $279.1 million of goodwill in connection with the acquisition of DBM (see Note 2).
	The Partnership evaluates goodwill for impairment annually (see Note 1). Estimating the fair value of the Partnership’s reporting units was not necessary based on the qualitative evaluation as of October 1, 2014, and no goodwill impairment has been recognized in these consolidated financial statements. Procedures were also performed in the fourth quarter of 2014 to review any changes in circumstances subsequent to the annual test, including changes in commodity prices. These procedures also indicated no impairment.
	Other intangible assets. The intangible asset balance in the consolidated balance sheets includes the fair value, net of amortization, of (i) contracts assumed by the Partnership in connection with the Platte Valley acquisition in February 2011, which are being amortized on a straight-line basis over 50 years, (ii) interconnect agreements at Chipeta entered into in November 2012, which are being amortized on a straight-line basis over 10 years, and (iii) contracts assumed by the Partnership in connection with the DBM acquisition in November 2014, which are being amortized on a straight-line basis over 30 years.
	The Partnership assesses intangible assets for impairment together with related underlying long-lived assets whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. See Property, plant and equipment in Note 1 for further discussion of management’s process to evaluate potential impairment of long-lived assets. No intangible asset impairment has been recognized in these consolidated financial statements.
	The following table presents the gross carrying amount and accumulated amortization of other intangible assets:
		December 31,
	thousands	2014			2013
	Gross carrying amount	$	892,555		$	56,988
	Accumulated amortization	(7,698		)	(3,382		)
	Other intangible assets	$	884,857		$	53,606
	Amortization expense for intangible assets was $4.3 million, $1.4 million and $1.1 million for the years ended December 31, 2014, 2013 and 2012, respectively. The Partnership estimates that it will record $29.1 million of intangible asset amortization during 2015 and $29.2 million for each of the following four years.

Equity_Investments

Equity Investments	12 Months Ended
	Dec. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]
Equity Investments	9. EQUITY INVESTMENTS
	The following table presents the activity in the Partnership’s equity investments for the years ended December 31, 2014 and 2013:
		Equity Investments
	thousands	Fort			White			Rendezvous (3)			Mont			TEG (5)			TEP (6)			FRP (7)			Total
		Union (1)			Cliffs (2)						Belvieu JV (4)
	Balance at December 31, 2012	$	23,453		$	17,567		$	65,110		$	—		$	9,033		$	80,737		$	23,866		$	219,766
	Initial investment	—			—			—			78,129			—			—			—			78,129
	Investment earnings (loss), net of amortization	6,273			9,681			2,088			5,690			93			(776		)	(101		)	22,948
	Contributions	16			19,087			—			37,309			6,732			108,969			105,547			277,660
	Capitalized interest	—			—			—			1,352			791			8,801			6,089			17,033
	Distributions	(4,570		)	(9,099		)	(4,029		)	—			—			—			—			(17,698		)
	Distributions in excess of cumulative earnings (8)	—			(2,197		)	(2,241		)	—			—			—			—			(4,438		)
	Balance at December 31, 2013	$	25,172		$	35,039		$	60,928		$	122,480		$	16,649		$	197,731		$	135,401		$	593,400
	Investment earnings (loss), net of amortization	6,344			11,912			1,729			29,029			650			6,108			2,064			57,836
	Contributions	—			10,456			—			3,957			352			6,623			42,033			63,421
	Capitalized interest	—			—			—			—			—			—			857			857
	Distributions	(5,583		)	(11,330		)	(3,669		)	(34,129		)	(523		)	(5,622		)	(2,111		)	(62,967		)
	Distributions in excess of cumulative earnings (8)	—			(1,762		)	(2,652		)	—			(338		)	(6,047		)	(7,256		)	(18,055		)
	Balance at December 31, 2014	$	25,933		$	44,315		$	56,336		$	121,337		$	16,790		$	198,793		$	170,988		$	634,492
	(1)	The Partnership has a 14.81% interest in Fort Union, a joint venture that owns a gathering pipeline and treating facilities in the Powder River Basin. Anadarko is the construction manager and physical operator of the Fort Union facilities. Certain business decisions, including, but not limited to, decisions with respect to significant expenditures or contractual commitments, annual budgets, material financings, dispositions of assets or amending the owners’ firm gathering agreements, require 65% or unanimous approval of the owners.
	(2)	The Partnership has a 10% interest in White Cliffs, a limited liability company that owns a crude oil pipeline that originates in Platteville, Colorado and terminates in Cushing, Oklahoma. The third-party majority owner is the manager of the White Cliffs operations. Certain business decisions, including, but not limited to, approval of annual budgets and decisions with respect to significant expenditures, contractual commitments, acquisitions, material financings, dispositions of assets or admitting new members, require more than 75% approval of the members.
	(3)	The Partnership has a 22% interest in Rendezvous, a limited liability company that operates gas gathering facilities in Southwestern Wyoming. Certain business decisions, including, but not limited to, decisions with respect to significant expenditures or contractual commitments, annual budgets, material financings, dispositions of assets or amending the members’ gas servicing agreements, require unanimous approval of the members.
	(4)	The Partnership has a 25% interest in the Mont Belvieu JV, an entity formed to design, construct, and own two fractionation trains located in Mont Belvieu, Texas. A third party is the operator of the Mont Belvieu JV fractionation trains. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the creation, appointment, or removal of officer positions require 50% or unanimous approval of the owners.
	(5)	The Partnership has a 20% interest in TEG, an entity that consists of two NGL gathering systems that link natural gas processing plants to TEP. Enbridge Midcoast Energy, LP (“Enbridge”) is the operator of the two gathering systems. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the delegation, creation, appointment, or removal of officer positions require more than 50% approval of the members.
	(6)	The Partnership has a 20% interest in TEP, which consists of an NGL pipeline that originates in Skellytown, Texas and extends to Mont Belvieu, Texas. Enterprise Products Operating LLC (“Enterprise”) is the operator of TEP. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the creation, appointment, or removal of officer positions require more than 50% approval of the members.
	(7)	The Partnership has a 33.33% interest in the FRP, an NGL pipeline that extends from Weld County, Colorado to Skellytown, Texas. Enterprise is the operator of FRP. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the creation, appointment, or removal of officer positions require more than 50% approval of the members.
	(8)	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.
	9. EQUITY INVESTMENTS (CONTINUED)
	The investment balance at December 31, 2014, includes $2.3 million and $42.1 million for the purchase price allocated to the investment in Fort Union and Rendezvous, respectively, in excess of the historic cost basis of Western Gas Resources, Inc. (“WGRI”), the entity that previously owned the interests in Fort Union and Rendezvous, which Anadarko acquired in August 2006. This excess balance is attributable to the difference between the fair value and book value of such gathering and treating facilities (at the time WGRI was acquired by Anadarko) and is being amortized over the remaining estimated useful life of those facilities.
	The investment balance in White Cliffs at December 31, 2014, is $9.0 million less than the Partnership’s underlying equity in White Cliffs’ net assets, primarily due to the Partnership recording the acquisition of its initial 0.4% interest in White Cliffs at Anadarko’s historic carrying value. This difference is being amortized to equity income, net over the remaining estimated useful life of the White Cliffs pipeline.
	Management evaluates its equity investments for impairment whenever events or changes in circumstances indicate that the carrying value of such investments may have experienced a decline in value that is other than temporary. When evidence of loss in value has occurred, management compares the estimated fair value of the investment to the carrying value of the investment to determine whether the investment has been impaired. Management assesses the fair value of equity investments using commonly accepted techniques, and may use more than one method, including, but not limited to, recent third-party comparable sales and discounted cash flow models. If the estimated fair value is less than the carrying value, the excess of the carrying value over the estimated fair value is recognized as an impairment loss.
	The following tables present the summarized combined financial information for the Partnership’s equity investments (amounts represent 100% of investee financial information):
			Year Ended December 31,
	thousands		2014			2013			2012
	Consolidated Statements of Income
	Revenues		$	548,629		$	261,705		$	199,764
	Operating income		336,188			171,496			135,498
	Net income		333,705			170,175			133,987
			December 31,
	thousands		2014			2013
	Consolidated Balance Sheets
	Current assets		$	141,781		$	186,690
	Property, plant and equipment, net		2,814,336			2,676,531
	Other assets		48,799			38,258
	Total assets		$	3,004,916		$	2,901,479
	Current liabilities		95,102			206,602
	Non-current liabilities		22,615			34,012
	Equity		2,887,199			2,660,865
	Total liabilities and equity		$	3,004,916		$	2,901,479

Components_of_Working_Capital

Components of Working Capital	12 Months Ended
	Dec. 31, 2014
Components Of Working Capital [Abstract]
Components of Working Capital	10.  COMPONENTS OF WORKING CAPITAL
	A summary of other current assets is as follows:
		December 31,
	thousands	2014		2013
	Natural gas liquids inventory	$	5,316	$	2,584
	Natural gas imbalance receivables	415		3,605
	Prepaid insurance	2,443		2,123
	Other	1,893		1,710
	Total other current assets	$	10,067	$	10,022
	A summary of accrued liabilities is as follows:
		December 31,
	thousands	2014		2013
	Accrued capital expenditures	$	116,891	$	94,750
	Accrued plant purchases	14,023		21,396
	Accrued interest expense	24,741		18,119
	Short-term asset retirement obligations	1,212		1,966
	Short-term remediation and reclamation obligations	475		562
	Income taxes payable	207		—
	Other	1,106		218
	Total accrued liabilities	$	158,655	$	137,011

Asset_Retirement_Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	11.  ASSET RETIREMENT OBLIGATIONS
	The following table provides a summary of changes in asset retirement obligations:
		Year Ended December 31,
	thousands	2014			2013
	Carrying amount of asset retirement obligations at beginning of year	$	78,035		$	66,723
	Liabilities incurred	13,769			14,143
	Liabilities settled	(4,181		)	(1,943		)
	Accretion expense	4,846			4,326
	Revisions in estimated liabilities	16,623			(5,214		)
	Carrying amount of asset retirement obligations at end of year	$	109,092		$	78,035
	Revisions in estimated liabilities for the year ended December 31, 2014, are related to changes in estimated inflation rates, changes in property lives and changes in the expected timing of settlement primarily at the DJ Basin complex, Granger complex, Hugoton and Hilight systems, MIGC, OTTCO, Brasada complex and Non-Operated Marcellus Interest systems. The liabilities incurred for the year ended December 31, 2014, increased primarily due to the acquisition of DBM in the fourth quarter of 2014 and continued capital expansion at the DJ Basin complex.
	Revisions in estimated liabilities for the year ended December 31, 2013, related primarily to the change in the estimated timing of settling the Partnership’s asset retirement obligations at the DJ Basin complex. The liabilities incurred for the year ended December 31, 2013, represented the increase in capital expansion at the DJ Basin complex, the Hilight system and the June 2013 completion of the Brasada complex.

Debt_and_Interest_Expense

Debt and Interest Expense	12 Months Ended
	Dec. 31, 2014
Debt Instruments [Abstract]
Debt and Interest Expense	12.  DEBT AND INTEREST EXPENSE
	At December 31, 2014, 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 RCF. The two tranches of the 2022 Notes, issued in June and October 2012, were issued under the same indenture and are considered a single class of securities. The two tranches of the 2018 Notes, issued in August 2013 and March 2014, were issued under the same indenture and are considered a single class of securities.
	The following table presents the Partnership’s outstanding debt as of December 31, 2014 and 2013:
			December 31, 2014									31-Dec-13
	thousands		Principal			Carrying			Fair			Principal		Carrying		Fair
						Value			Value (1)					Value		Value (1)
	5.375% Senior Notes due 2021		$	500,000		$	495,714		$	549,530		$	500,000	$	495,173	$	533,615
	4.000% Senior Notes due 2022		670,000			672,930			681,942			670,000		673,278		641,237
	Revolving credit facility		510,000			510,000			510,000			—		—		—
	2.600% Senior Notes due 2018		350,000			350,474			352,162			250,000		249,718		247,988
	5.450% Senior Notes due 2044		400,000			393,836			417,619			—		—		—
	Total long-term debt		$	2,430,000		$	2,422,954		$	2,511,253		$	1,420,000	$	1,418,169	$	1,422,840
	(1)	Fair value is measured using Level 2 inputs.
	Debt activity. The following table presents the debt activity of the Partnership for the years ended December 31, 2014 and 2013:
	thousands		Carrying Value
	Balance at December 31, 2012		$	1,168,278
	Revolving credit facility borrowings		710,000
	Repayments of revolving credit facility		(710,000		)
	Issuance of 2.600% Senior Notes due 2018		250,000
	Other		(109		)
	Balance at December 31, 2013		$	1,418,169
	Revolving credit facility borrowings		1,160,000
	Issuance of 5.450% Senior Notes due 2044		400,000
	Issuance of 2.600% Senior Notes due 2018		100,000
	Repayments of revolving credit facility		(650,000		)
	Other		(5,215		)
	Balance at December 31, 2014		$	2,422,954
	Senior Notes. The 2044 Notes issued in March 2014 were offered at a price to the public of 98.443% of the face amount. Including the effects of the issuance and underwriting discounts, the effective interest rate of the 2044 Notes is 5.633%. Interest is paid semi-annually on April 1 and October 1 of each year. Proceeds (net of underwriting discount of $3.5 million, original issue discount and debt issuance costs) were used to repay amounts then outstanding under the Partnership’s RCF and for general partnership purposes.
	The 2018 Notes issued in March 2014 were offered at a price to the public of 100.857% of the face amount. Including the effects of the issuance premium for the March 2014 offering, the issuance discount for the August 2013 offering of 2018 Notes and underwriting discounts, the effective interest rate of the 2018 Notes is 2.743%. Interest is paid semi-annually on February 15 and August 15 of each year. Proceeds (net of underwriting discount of $0.6 million, original issue premium and debt issuance costs) were used to repay amounts then outstanding under the Partnership’s RCF and for general partnership purposes.
	12.  DEBT AND INTEREST EXPENSE (CONTINUED)
	At December 31, 2014, the Partnership was in compliance with all covenants under the indentures governing the 2021 Notes, 2022 Notes, 2018 Notes and 2044 Notes.
	Interest rate agreements. In May 2012, the Partnership entered into U.S. Treasury Rate lock agreements to mitigate the risk of rising interest rates prior to the issuance of the 2022 Notes. The Partnership settled the rate lock agreements simultaneously with the June 2012 offering of the 2022 Notes, realizing a loss of $1.7 million, which is included in other income (expense), net in the consolidated statements of income.
	Note payable to Anadarko. In 2008, the Partnership entered into a five-year $175.0 million term loan agreement with Anadarko. The interest rate was fixed at 2.82% prior to June 2012 when the note payable to Anadarko was repaid in full with proceeds from the June 2012 offering of the 2022 Notes.
	Revolving credit facility. In February 2014, the Partnership entered into its amended and restated $1.2 billion senior unsecured RCF, which is expandable to a maximum of $1.5 billion, replacing an $800.0 million credit facility, which was originally entered into in March 2011. Subsequent to February 2014, the Partnership borrowed $350.0 million under the RCF to fund the acquisition of the TEFR Interests (see Note 2). The RCF matures in February 2019 and bears interest at London Interbank Offered Rate (“LIBOR”), plus applicable margins ranging from 0.975% to 1.45%, or an alternate base rate equal to the greatest of (a) the Prime Rate, (b) the Federal Funds Effective Rate plus 0.5%, or (c) LIBOR plus 1%, in each case plus applicable margins currently ranging from zero to 0.45%, based upon the Partnership’s senior unsecured debt rating. The interest rate on the RCF was 1.47% at December 31, 2014. At December 31, 2013, the interest rate on the previous credit facility was 1.67%. The Partnership is required to pay a quarterly facility fee currently ranging from 0.15% to 0.30% of the commitment amount (whether used or unused), based upon the Partnership’s senior unsecured debt rating. The facility fee rate was 0.20% and 0.25% at December 31, 2014 and 2013, respectively.
	As of December 31, 2014, the Partnership had $510.0 million of outstanding borrowings, $12.8 million in outstanding letters of credit and $677.2 million available for borrowing under the RCF. At December 31, 2014, the Partnership was in compliance with all covenants under the RCF.
	The 2021 Notes, 2022 Notes, 2018 Notes, 2044 Notes and obligations under the RCF are recourse to the Partnership’s general partner. The Partnership’s general partner is indemnified by a wholly owned subsidiary of Anadarko, WGRI, against any claims made against the general partner under the 2022 Notes, 2021 Notes, and/or the RCF.
	In connection with the acquisitions of the Non-Operated Marcellus Interest, the Anadarko-Operated Marcellus Interest and the TEFR Interests, the Partnership’s general partner and other wholly owned subsidiaries of Anadarko entered into indemnification agreements, whereby such subsidiaries agreed to indemnify the Partnership’s general partner for any recourse liability it may have for RCF borrowings, or other debt financing, attributable to the acquisitions of the Non-Operated Marcellus Interest, the Anadarko-Operated Marcellus Interest and the TEFR Interests. These indemnification agreements apply to the 2044 Notes, 2018 Notes and/or RCF borrowings outstanding related to the aforementioned acquisitions.
	The Partnership’s general partner, the other indemnifying subsidiaries of Anadarko and WGRI also amended and restated the indemnity agreements between them to (i) conform language among all the indemnification agreements and (ii) reduce the amount for which WGRI would indemnify the Partnership’s general partner by an amount equal to any amounts payable to the Partnership’s general partner under the indemnification agreements related to the acquisitions of the Non-Operated Marcellus Interest, the Anadarko-Operated Marcellus Interest and the TEFR Interests.
	12.  DEBT AND INTEREST EXPENSE (CONTINUED)
	Interest expense. The following table summarizes the amounts included in interest expense:
			Year Ended December 31,
	thousands		2014			2013			2012
	Third parties
	Interest expense on long-term debt		$	81,495		$	59,293		$	41,171
	Amortization of debt issuance costs and commitment fees		5,103			4,449			4,319
	Capitalized interest		(9,832		)	(11,945		)	(6,196		)
	Total interest expense – third parties		76,766			51,797			39,294
	Affiliates
	Interest expense on note payable to Anadarko (1)		—			—			2,440
	Interest expense on affiliate balances (2)		—			—			326
	Total interest expense – affiliates		—			—			2,766
	Interest expense		$	76,766		$	51,797		$	42,060
	(1)	In June 2012, the note payable to Anadarko was repaid in full. See Note payable to Anadarko within this Note 12.
	(2)	Imputed interest expense on the reimbursement payable to Anadarko for certain expenditures Anadarko incurred in 2011 related to the construction of the Brasada complex and Lancaster plant. In the fourth quarter of 2012, the Partnership repaid the reimbursement payable to Anadarko associated with the construction of the Brasada complex and Lancaster plant.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	13.  COMMITMENTS AND CONTINGENCIES
	Environmental obligations. The Partnership is subject to various environmental-remediation obligations arising from federal, state and local regulations regarding air and water quality, hazardous and solid waste disposal and other environmental matters. As of December 31, 2014 and 2013, asset retirement obligations and other on the consolidated balance sheets included $1.5 million and $1.9 million, respectively, of long-term liability for remediation and reclamation obligations. The recorded obligations do not include any anticipated insurance recoveries. The majority of payments related to these obligations are expected to be made over the next five years. Management regularly monitors the remediation and reclamation process and the liabilities recorded and believes that the amounts reflected in the Partnership’s recorded environmental obligations are adequate to fund remedial actions to comply with present laws and regulations, and that the ultimate liability for these matters, if any, will not differ materially from recorded amounts nor materially affect the Partnership’s overall results of operations, cash flows or financial condition. There can be no assurance, however, that current regulatory requirements will not change, or past non-compliance with environmental issues will not be discovered. See Note 10 and Note 11.
	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.
	13.  COMMITMENTS AND CONTINGENCIES (CONTINUED)
	In July 2011, the Court denied the defendants’ motion to dismiss without ruling on the merits. In August 2014, the judge scheduled a jury trial for July 2015. In preparation for trial, the parties amended their pleadings in October 2014 and are 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 December 31, 2014, the Partnership had unconditional payment obligations for services to be rendered or products to be delivered in connection with its capital projects of $64.1 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.
	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 2015.
	Rent expense associated with the office, warehouse and equipment leases was $3.5 million, $2.8 million and $3.0 million for the years ended December 31, 2014, 2013 and 2012, respectively.
	The amounts in the table below represent existing contractual operating lease obligations as of December 31, 2014, that may be assigned or otherwise charged to the Partnership pursuant to the reimbursement provisions of the omnibus agreement:
	thousands	Operating Leases
	2015	$	338
	2016	303
	2017	157
	2018	34
	2019	—
	Thereafter	—
	Total	$	832

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business combinations policy	Presentation of Partnership assets. The term “Partnership assets” refers to the assets owned and interests accounted for under the equity method (see Note 9) by the Partnership as of December 31, 2014. 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 (see Note 2). 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.
	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.
Noncontrolling interests policy	In July 2009, the Partnership acquired a 51% interest in Chipeta Processing LLC (“Chipeta”) and became party to Chipeta’s limited liability company agreement (the “Chipeta LLC agreement”). On August 1, 2012, the Partnership acquired Anadarko’s then-remaining 24% membership interest in Chipeta (the “additional Chipeta interest”). Prior to this transaction, the interests in Chipeta held by Anadarko and a third-party member were reflected as noncontrolling interests in the consolidated financial statements. The acquisition of the additional Chipeta interest was accounted for on a prospective basis as the Partnership acquired an additional interest in an already-consolidated entity. As such, effective August 1, 2012, noncontrolling interest excludes the financial results and operations of the additional Chipeta interest. The remaining 25% membership interest held by the third-party member is reflected within noncontrolling interests in the consolidated financial statements for all periods presented. See Note 2.
Use of estimates policy	Use of estimates. 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 under the particular circumstances. 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.
Fair value policy	Fair value. The fair-value-measurement standard defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The standard characterizes inputs used in determining fair value according to a hierarchy that prioritizes those inputs based upon the degree to which they are observable. The three levels of the fair value hierarchy are as follows:
	Level 1 – Inputs represent quoted prices in active markets for identical assets or liabilities.
	Level 2 – Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly (for example, quoted market prices for similar assets or liabilities in active markets or quoted market prices for identical assets or liabilities in markets not considered to be active, inputs other than quoted prices that are observable for the asset or liability, or market-corroborated inputs).
	Level 3 – Inputs that are not observable from objective sources, such as management’s internally developed assumptions used in pricing an asset or liability (for example, an estimate of future cash flows used in management’s internally developed present value of future cash flows model that underlies the fair value measurement).
	Nonfinancial assets and liabilities initially measured at fair value include certain assets and liabilities acquired in a third-party business combination, assets and liabilities exchanged in non-monetary transactions, long-lived assets (asset groups), goodwill and other intangibles, initial recognition of asset retirement obligations, and initial recognition of environmental obligations assumed in a third-party acquisition. Impairment analyses for long-lived assets, goodwill and other intangibles, and the initial recognition of asset retirement obligations and environmental obligations use Level 3 inputs. When the Partnership is required to measure fair value and there is not a market-observable price for the asset or liability or a market-observable price for a similar asset or liability, the Partnership uses the cost, income, or market valuation approach depending on the quality of information available to support management’s assumptions.
	The fair value of debt reflects any premium or discount for the difference between the stated interest rate and the quarter-end market interest rate, and is based on quoted market prices for identical instruments, if available, or based on valuations of similar debt instruments. See Note 12.
	The carrying amounts of cash and cash equivalents, accounts receivable and accounts payable reported on the consolidated balance sheets approximate fair value due to the short-term nature of these items.
	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 C units”) until the end of 2017 (unless earlier converted, see Note 4), 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 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 C distributions at fair value at the time of issuance. This fair value measurement uses the Partnership’s unit price as a significant input in the determination of the fair value and thus represents a Level 2 measurement. On February 12, 2015, the Partnership’s general partner distributed 45,711 PIK C units to the Class C unitholder, based on the $0.700 common unit distribution referenced above, 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 Anadarko. Concurrently with the closing of the Partnership’s May 2008 IPO, 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 $317.8 million and $296.7 million at December 31, 2014 and 2013, 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.
	During 2014, the Partnership recognized impairments of $3.1 million, primarily related to a non-operational plant in the Powder River Basin that was impaired to its estimated fair value of $2.4 million, using Level 3 fair-value inputs, the cancellation of various capital projects by the third-party operator of the Non-Operated Marcellus Interest systems and a compressor no longer in service at the Hilight system.
	During 2012, the Partnership recognized a $6.0 million impairment related to a gathering system in central Wyoming that was impaired to its estimated fair value using Level 3 fair-value inputs and an impairment of $0.6 million for the original installation costs on a compressor relocated within the Partnership’s operating assets.
Cash equivalents policy	Cash equivalents. The Partnership considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents.
Bad-debt reserve policy	Bad-debt reserve. The Partnership’s revenues are primarily from Anadarko, for which no credit limit is maintained. The Partnership analyzes its exposure to bad debts on a customer-by-customer basis for its third-party accounts receivable and may establish credit limits for significant third-party customers. As of December 31, 2014 and 2013, the Partnership’s bad-debt reserve was immaterial.
Natural gas imbalances policy	Natural gas imbalances. The consolidated balance sheets include natural gas imbalance receivables and payables resulting from differences in gas volumes received into the Partnership’s systems and gas volumes delivered by the Partnership to customers’ pipelines. Natural gas volumes owed to or by the Partnership that are subject to monthly cash settlement are valued according to the terms of the contract as of the balance sheet dates and reflect market index prices. Other natural gas volumes owed to or by the Partnership are valued at the Partnership’s weighted-average cost of natural gas as of the balance sheet dates and are settled in-kind. As of December 31, 2014, natural gas imbalance receivables and payables were $0.4 million and $0.7 million, respectively. As of December 31, 2013, natural gas imbalance receivables and payables were $3.6 million and $2.5 million, respectively. Changes in natural gas imbalances are reported in other revenues for imbalance receivables or in cost of product for imbalance payables.
Inventory policy	Inventory. The cost of NGLs inventories is determined by the weighted-average cost method on a location-by-location basis. Inventory is stated at the lower of weighted-average cost or market value and is reported in other current assets in the consolidated balance sheets. See Note 10.
Property, plant and equipment policy	Property, plant and equipment. Property, plant and equipment are generally stated at the lower of historical cost less accumulated depreciation or fair value, if impaired. Because acquisitions of assets from Anadarko are transfers of net assets between entities under common control, the assets acquired from Anadarko are initially recorded at Anadarko’s historic carrying value. The difference between the carrying value of net assets acquired from Anadarko and the consideration paid is recorded as an adjustment to partners’ capital.
	Assets acquired in a business combination or non-monetary exchange with a third party are initially recorded at fair value. All construction-related direct labor and material costs are capitalized. The cost of renewals and betterments that extend the useful life of property, plant and equipment is also capitalized. The cost of repairs, replacements and major maintenance projects that do not extend the useful life or increase the expected output of property, plant and equipment is expensed as incurred.
	Depreciation is computed using the straight-line method based on estimated useful lives and salvage values of assets. However, subsequent events could cause a change in estimates, thereby impacting future depreciation amounts. Uncertainties that may impact these estimates include, but are not limited to, changes in laws and regulations relating to environmental matters, including air and water quality, restoration and abandonment requirements, economic conditions, and supply and demand in the area.
	Management evaluates the ability to recover the carrying amount of its long-lived assets to determine whether its long-lived assets have been impaired. Impairments exist when the carrying amount of an asset exceeds estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. When alternative courses of action to recover the carrying amount of a long-lived asset are under consideration, estimates of future undiscounted cash flows take into account possible outcomes and probabilities of their occurrence. If the carrying amount of the long-lived asset is not recoverable based on the estimated future undiscounted cash flows, the impairment loss is measured as the excess of the asset’s carrying amount over its estimated fair value, such that the asset’s carrying amount is adjusted to its estimated fair value with an offsetting charge to impairment expense. Refer to Note 7 for a description of impairments recorded during the years ended December 31, 2014, 2013 and 2012.
	Contributions in aid of construction costs from affiliates. In 2013, a subsidiary of Anadarko entered into an aid in construction agreement with the Partnership, whereby the Partnership constructed five receipt-point facilities at the Brasada complex that serve the Anadarko subsidiary. Such subsidiary reimbursed the Partnership for costs associated with construction of the receipt points. These reimbursements are presented within the investing section of the Partnership’s consolidated statements of cash flows as “Contributions in aid of construction costs from affiliates.”
Capitalized interest policy	Capitalized interest. Interest is capitalized as part of the historical cost of constructing assets for significant projects that are in progress. Capitalized interest is determined by multiplying the Partnership’s weighted-average borrowing cost on debt by the average amount of qualifying costs incurred. Once the construction of an asset subject to interest capitalization is completed and the asset is placed in service, the associated capitalized interest is expensed through depreciation or impairment, together with other capitalized costs related to that asset.
Goodwill policy	Goodwill. Goodwill is recorded when the purchase price of a business acquired exceeds the fair market value of the tangible and separately measurable intangible net assets. Refer to Note 8 for a discussion of goodwill. The Partnership evaluates goodwill for impairment annually, as of October 1, or more often as facts and circumstances warrant. The Partnership has allocated goodwill on its two reporting units: (i) gathering and processing and (ii) transportation. An initial qualitative assessment may be performed prior to proceeding to the comparison of the fair value of each reporting unit to which goodwill has been assigned, to the carrying amount of net assets, including goodwill, of each reporting unit. If the Partnership concludes, based on qualitative factors, that it is more likely than not that the fair value of the reporting unit exceeds its carrying amount, then goodwill is not impaired, and estimating the fair value of the reporting unit is not necessary. If the carrying amount of the reporting unit exceeds its fair value, goodwill is written down to its implied fair value through a charge to operating expense based on a hypothetical purchase price allocation. The carrying value of goodwill after such an impairment would represent a Level 3 fair value measurement.
Other intangible assets policy	Other intangible assets. The Partnership assesses intangible assets, as described in Note 8, for impairment together with related underlying long-lived assets whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. See Property, plant and equipment within this Note 1 for further discussion of management’s process to evaluate potential impairment of long-lived assets.
Asset retirement obligations and environmental expenditures policy	Asset retirement obligations. Management recognizes a liability based on the estimated costs of retiring tangible long-lived assets. The liability is recognized at fair value, measured using discounted expected future cash outflows for the asset retirement obligation when the obligation originates, which generally is when an asset is acquired or constructed. The carrying amount of the associated asset is increased commensurate with the liability recognized. Over time, the discounted liability is adjusted to its expected settlement value through accretion expense, which is reported within depreciation, amortization and impairments in the consolidated statements of income. Subsequent to the initial recognition, the liability is also adjusted for any changes in the expected value of the retirement obligation (with a corresponding adjustment to property, plant and equipment) until the obligation is settled. Revisions in estimated asset retirement obligations may result from changes in estimated inflation rates, discount rates, asset retirement costs and the estimated timing of settling asset retirement obligations. See Note 11.
	Environmental expenditures. The Partnership expenses environmental obligations related to conditions caused by past operations that do not generate current or future revenues. Environmental obligations related to operations that generate current or future revenues are expensed or capitalized, as appropriate. Liabilities are recorded when the necessity for environmental remediation or other potential environmental liabilities becomes probable and the costs can be reasonably estimated. Accruals for estimated losses from environmental remediation obligations are recognized no later than at the time of the completion of the remediation feasibility study. These accruals are adjusted as additional information becomes available or as circumstances change. Costs of future expenditures for environmental-remediation obligations are not discounted to their present value. See Note 13.
Segments policy	Segments. The Partnership’s operations are organized into a single operating segment, the assets of which gather, process, compress, treat and transport Anadarko and third-party natural gas, condensate, NGLs and crude oil in the United States.
Revenues and cost of product policy	Revenues and cost of product. Under its fee-based gathering, treating and processing arrangements, the Partnership is paid a fixed fee based on the volume and thermal content of natural gas and recognizes revenues for its services in the month such services are performed. Producers’ wells are connected to the Partnership’s gathering systems for delivery of natural gas to the Partnership’s processing or treating plants, where the natural gas is processed to extract NGLs and condensate or treated in order to satisfy pipeline specifications. In some areas, where no processing is required, the producers’ gas is gathered and delivered to pipelines for market delivery. Under cost-of-service gathering agreements, the Partnership earns fees for gathering and compression services based on rates calculated in a cost-of-service model and reviewed periodically over the life of the agreements. Under percent-of-proceeds contracts, revenue is recognized when the natural gas, NGLs or condensate are sold. The percentage of the product sale ultimately paid to the producer is recorded as a related cost of product expense.
	The Partnership purchases natural gas volumes at the wellhead for gathering and processing. As a result, the Partnership has volumes of NGLs and condensate to sell and volumes of residue to either sell, to use for system fuel or to satisfy keep-whole obligations. In addition, depending upon specific contract terms, condensate and NGLs recovered during gathering and processing are either returned to the producer or retained and sold. Under keep-whole contracts, when condensate or NGLs are retained and sold, producers are kept whole for the condensate or NGL volumes through the receipt of a thermally equivalent volume of residue. The keep-whole contract conveys an economic benefit to the Partnership when the combined value of the individual NGLs is greater in the form of liquids than as a component of the natural gas stream; however, the Partnership is adversely impacted when the value of the NGLs is lower than the value of the natural gas stream including the liquids. The Partnership has commodity price swap agreements with Anadarko to mitigate exposure to a substantial majority of the commodity price uncertainty that would otherwise be present as a result of the purchase and sale of natural gas, condensate or NGLs. See Note 5. Revenue is recognized from the sale of condensate and NGLs upon transfer of title and related purchases are recorded as cost of product.
	The Partnership earns transportation revenues through firm contracts that obligate each of its customers to pay a monthly reservation or demand charge regardless of the pipeline capacity used by that customer. An additional commodity usage fee is charged to the customer based on the actual volume of natural gas transported. Transportation revenues are also generated from interruptible contracts pursuant to which a fee is charged to the customer based on volumes transported through the pipeline. Revenues for transportation of natural gas and NGLs are recognized over the period of firm transportation contracts or, in the case of usage fees and interruptible contracts, when the volumes are received into the pipeline. From time to time, certain revenues may be subject to refund pending the outcome of rate matters before the Federal Energy Regulatory Commission (the “FERC”) and reserves are established where appropriate.
	Proceeds from the sale of residue, NGLs and condensate are reported as revenues from natural gas, natural gas liquids and condensate sales in the consolidated statements of income. Revenues attributable to the fixed-fee component of gathering and processing contracts as well as demand charges and commodity usage fees on transportation contracts are reported as revenues from gathering, processing and transportation of natural gas and natural gas liquids in the consolidated statements of income.
Equity-based compensation policy	Equity-based compensation. Phantom unit awards are granted under the Western Gas Partners, LP 2008 Long-Term Incentive Plan (the “WES LTIP”). The WES LTIP was adopted by the general partner of the Partnership and permits the issuance of up to 2,250,000 units, of which 2,133,227 units remained available for future issuance as of December 31, 2014. Upon vesting of each phantom unit awarded under the WES LTIP, the holder will receive common units of the Partnership or, at the discretion of the general partner’s Board of Directors, cash in an amount equal to the market value of common units of the Partnership on the vesting date. Equity-based compensation expense attributable to grants made under the WES LTIP impact the Partnership’s cash flows from operating activities only to the extent cash payments are made to a participant in lieu of issuance of common units to the participant. The Partnership amortizes stock-based compensation expense attributable to awards granted under the WES LTIP over the vesting periods applicable to the awards.
	Additionally, the Partnership’s general and administrative expenses include equity-based compensation costs allocated by Anadarko to the Partnership for grants made pursuant to (i) the Western Gas Equity Partners, LP 2012 Long-Term Incentive Plan (the “WGP LTIP”) for the years ended December 31, 2014 and 2013, (ii) the Western Gas Holdings, LLC Equity Incentive Plan, as amended and restated (the “Incentive Plan”) for the year ended December 31, 2012, and (iii) the Anadarko Petroleum Corporation 1999 Stock Incentive Plan and the Anadarko Petroleum Corporation 2008 and 2012 Omnibus Incentive Compensation Plans (Anadarko’s plans are referred to collectively as the “Anadarko Incentive Plans”) for all periods presented. Grants made under equity-based compensation plans result in equity-based compensation expense, which is determined by reference to the fair value of equity compensation. For equity-based awards ultimately settled through the issuance of units or stock, the fair value is measured as of the date of the relevant equity grant. Equity-based compensation granted under the WGP LTIP and the Anadarko Incentive Plans does not impact the Partnership’s cash flows from operating activities since the offset to compensation expense is recorded as a contribution to partners’ capital in the consolidated financial statements at the time of contribution, when the expense is realized. However, distribution equivalent rights awarded in tandem with equity-or liability-based awards are paid in cash and reflected within financing cash flows in the consolidated statements of cash flows. See Note 5.
Income taxes policy	Income taxes. The Partnership generally is not subject to federal income tax or state income tax other than Texas margin tax on the portion of its income that is apportionable to Texas. Deferred state income taxes are recorded on temporary differences between the financial statement carrying amounts of assets and liabilities and their respective tax bases. The Partnership routinely assesses the realizability of its deferred tax assets. If the Partnership concludes that it is more likely than not that some of the deferred tax assets will not be realized, the tax asset is reduced by a valuation allowance. Federal and state current and deferred income tax expense was recorded on the Partnership assets prior to the Partnership’s acquisition of these assets from Anadarko.
	For periods beginning on and subsequent to the Partnership’s acquisition of the Partnership assets, the Partnership makes payments to Anadarko pursuant to the tax sharing agreement entered into between Anadarko and the Partnership for its estimated share of taxes from all forms of taxation, excluding taxes imposed by the United States, that are included in any combined or consolidated returns filed by Anadarko. The aggregate difference in the basis of the Partnership’s assets for financial and tax reporting purposes cannot be readily determined as the Partnership does not have access to information about each partner’s tax attributes in the Partnership.
	The accounting standards for uncertain tax positions defines the criteria an individual tax position must satisfy for any part of the benefit of that position to be recognized in the financial statements. The Partnership had no material uncertain tax positions at December 31, 2014 or 2013.
	With respect to assets acquired from Anadarko, the Partnership recorded Anadarko’s historic current and deferred income taxes for the periods prior to the Partnership’s ownership of the assets. For periods subsequent to the Partnership’s acquisition, the Partnership is not subject to tax except for the Texas margin tax and, accordingly, does not record current and deferred federal income taxes related to the assets acquired from Anadarko.
Net income per common unit policy	Net income per common unit. The Partnership applies the two-class method in determining net income per unit applicable to master limited partnerships having multiple classes of securities including common units, Class C units, general partner units and IDRs. The two-class method is an earnings allocation formula that treats participating securities as having rights to earnings that otherwise would have been available to common unitholders. Under the two-class method, net income per unit is calculated as if all of the earnings for the period were distributed pursuant to the terms of the relevant contractual arrangement. The accounting guidance provides the methodology for and circumstances under which undistributed earnings are allocated to the general partner, limited partners and IDR holders. For the Partnership, earnings per unit is calculated based on the assumption that the Partnership distributes to its unitholders an amount of cash equal to the net income of the Partnership, notwithstanding the general partner’s ultimate discretion over the amount of cash to be distributed for the period, the existence of other legal or contractual limitations that would prevent distributions of all of the net income for the period or any other economic or practical limitation on the ability to make a full distribution of all of the net income for the period.
	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 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 (see discussion of Class C beneficial conversion feature and related impacts on earnings per unit in Note 4). Specifically, net income equal to the amount of available cash (as defined by the partnership agreement) is allocated to the general partner, common and Class C unitholders consistent with actual cash distributions and capital account allocations, including incentive distributions allocable to the general partner. Undistributed earnings (net income in excess of distributions) or undistributed losses (available cash in excess of net income) are then allocated to the general partner, common unitholders and Class C unitholders in accordance with their respective weighted-average ownership percentages during each period. 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 and Class C unit. See Note 4.
Recently issued accounting standards policy	Recently issued accounting standards. Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers, 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 to which the entity expects to be entitled 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 currently evaluating the impact of the adoption of this ASU on its consolidated financial statements.
	ASU 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, changes the criteria for reporting discontinued operations and requires additional disclosures, both for discontinued operations and for individually significant dispositions and assets classified as held for sale not qualifying as discontinued operations. This ASU is effective for annual and interim periods beginning in 2015, with early adoption permitted for disposals or for assets classified as held for sale that have not been reported in previously issued financial statements. The Partnership early adopted this ASU on a prospective basis beginning with the first quarter of 2014. The adoption did not have a material impact on the Partnership’s consolidated financial statements.
	ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists, requires that an unrecognized tax benefit, or a portion of an unrecognized tax benefit, be presented in the financial statements as a reduction to a deferred tax asset, except in certain circumstances. This ASU is effective for annual and interim periods beginning in 2014. The Partnership adopted this ASU on a prospective basis beginning with the first quarter of 2014. The adoption did not have a material impact on the Partnership’s consolidated financial statements. See Note 6—Income Taxes.
Equity investments policy	Management evaluates its equity investments for impairment whenever events or changes in circumstances indicate that the carrying value of such investments may have experienced a decline in value that is other than temporary. When evidence of loss in value has occurred, management compares the estimated fair value of the investment to the carrying value of the investment to determine whether the investment has been impaired. Management assesses the fair value of equity investments using commonly accepted techniques, and may use more than one method, including, but not limited to, recent third-party comparable sales and discounted cash flow models. If the estimated fair value is less than the carrying value, the excess of the carrying value over the estimated fair value is recognized as an impairment loss.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Assets and Investments Table	As of December 31, 2014, 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	1	5	2
	Natural gas treating facilities	8	—	—	1
	Natural gas processing facilities	13	3	—	2
	NGL pipelines	3	—	—	3
	Natural gas pipelines	4	—	—	—
	Oil pipeline	1	—	—	1

Acquisitions_tables

Acquisitions (tables)	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Acquisitions Table	The following table presents the acquisitions completed by the Partnership during the years ended December 31, 2014, 2013 and 2012, and identifies the funding sources for such acquisitions:
	thousands except unit and percent amounts		Acquisition		Percentage			Borrowings		Cash		Common	Class C	GP Units
			Date		Acquired					On Hand		Units Issued to Anadarko	Units Issued to Anadarko	Issued
	MGR (1)		1/13/12		100	%		$	299,000	$	159,587	632,783	—	12,914
	Chipeta (2)		8/1/12		24	%		—		128,250		151,235	—	3,086
	Non-Operated Marcellus Interest (3)		3/1/13		33.75	%		250,000		215,500		449,129	—	—
	Anadarko-Operated Marcellus Interest (4)		3/8/13		33.75	%		133,500		—		—	—	—
	Mont Belvieu JV (5)		6/5/13		25	%		—		78,129		—	—	—
	OTTCO (6)		9/3/13		100	%		27,500		—		—	—	—
	TEFR Interests (7)		3/3/14		Various (7)			350,000		6,250		308,490	—	—
	DBM (8)		11/25/14		100	%		475,000		298,327		—	10,913,853	—
	(1)	The assets acquired from Anadarko consisted of (i) the “Red Desert complex,” which is located in the greater Green River Basin in southwestern Wyoming, and includes the Patrick Draw processing plant, the Red Desert processing plant, gathering lines, and related facilities, (ii) a 22% interest in Rendezvous, which owns a gathering system serving the Jonah and Pinedale Anticline fields in southwestern Wyoming, and (iii) certain additional midstream assets and equipment. These assets are collectively referred to as the “MGR assets” and the acquisition as the “MGR acquisition.”
	(2)	The Partnership acquired Anadarko’s additional Chipeta interest (as described in Note 1). The Partnership received distributions related to the additional interest beginning July 1, 2012. This transaction brought the Partnership’s total membership interest in Chipeta to 75%. The remaining 25% membership interest in Chipeta held by a third-party member is reflected as noncontrolling interests in the consolidated financial statements for all periods presented.
	(3)	The Partnership acquired Anadarko’s 33.75% interest (non-operated) (the “Non-Operated Marcellus Interest”) in the Liberty and Rome gas gathering systems (the “Non-Operated Marcellus Interest systems”), serving production from the Marcellus shale in North-central Pennsylvania. In connection with the issuance of the common units, the Partnership’s general partner purchased 9,166 general partner units for consideration of $0.5 million.
	(4)	The Partnership acquired a 33.75% interest (the “Anadarko-Operated Marcellus Interest”) in each of the Larry’s Creek, Seely and Warrensville gas gathering systems (the “Anadarko-Operated Marcellus Interest systems”), which are operated by Anadarko and serve production from the Marcellus shale in North-central Pennsylvania, from a third party. During the third quarter of 2013, the Partnership recorded a $1.1 million decrease in the assets acquired and liabilities assumed in the acquisition, representing the final purchase price allocation.
	(5)	The Partnership acquired a 25% interest in the Mont Belvieu JV, an entity formed to design, construct, and own two fractionation trains located in Mont Belvieu, Texas, from a third party. The interest acquired is accounted for under the equity method of accounting.
	(6)	The Partnership acquired Overland Trail Transmission, LLC (“OTTCO”), a Delaware limited liability company, from a third party. OTTCO owns and operates an intrastate pipeline that connects the Partnership’s Red Desert and Granger complexes in southwestern Wyoming.
	(7)	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.
	(8)	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 serve production from Reeves, Loving and Culberson Counties, Texas and Eddy and Lea Counties, New Mexico. These assets are referred to collectively as the “DBM complex.” See Note 4 for a discussion of the Class C units.
Purchase Price Allocation Table	The following is the preliminary allocation of the purchase price to the assets acquired and liabilities assumed in the DBM acquisition as of the acquisition date, pending the acquired entity’s final financial statements:
	thousands
	Current assets		$	46,358
	Property, plant and equipment		440,971
	Goodwill		279,051
	Other intangible assets		835,566
	Accounts payables		(13,064		)
	Accrued liabilities		(24,824		)
	Deferred income taxes		(1,450		)
	Asset retirement obligations and other		(8,649		)
	Total purchase price		$	1,553,959
Pro Forma Condensed Financial Information Table	The following table presents pro forma condensed financial information of the Partnership as if the DBM acquisition had occurred on January 1, 2013:
			Year Ended December 31,
	thousands except per-unit amounts		2014				2013
	Revenues		$	1,397,030			$	1,107,030
	Net income		332,420				239,382
	Net income attributable to Western Gas Partners, LP		318,395				228,566
	Net income per common unit – basic and diluted		1.34				1.12

Partnership_Distributions_tabl

Partnership Distributions (tables)	12 Months Ended
	Dec. 31, 2014
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
	2012
	31-Mar			$	0.46		$	46,053	May-12
	30-Jun			0.48			52,425		August 2012
	30-Sep			0.5			56,346		Nov-12
	31-Dec			0.52			65,657		Feb-13
	2013
	31-Mar			$	0.54		$	70,143	May 2013
	30-Jun			0.56			79,315		Aug-13
	30-Sep			0.58			83,986		Nov-13
	31-Dec			0.6			92,609		Feb-14
	2014
	31-Mar			$	0.625		$	98,749	May 2014
	30-Jun			0.65			105,655		Aug-14
	30-Sep			0.675			111,608		Nov-14
	December 31 (1)			0.7			126,044		Feb-15
	(1)	On January 22, 2015, the Board of Directors of the Partnership’s general partner declared a cash distribution to the Partnership’s unitholders of $0.700 per unit, or $126.0 million in aggregate, including incentive distributions, but excluding distributions on Class C units (see Class C unit distributions below). The cash distribution was paid on February 12, 2015, to unitholders of record at the close of business on February 2, 2015.
Incentive Distribution Rights Table	The Partnership’s general partner, as the holder of the IDRs, was entitled to incentive distributions at the maximum distribution sharing percentage of 48.0% for all periods presented.
			Total Quarterly Distribution		Marginal Percentage
			Target Amount		Interest in Distributions
					Unitholders	General Partner
	Minimum quarterly distribution		$0.30		98.10%	1.90%
	First target distribution		up to $0.345		98.10%	1.90%
	Second target distribution		above $0.345 up to $0.375		85.10%	14.90%
	Third target distribution		above $0.375 up to $0.450		75.10%	24.90%
	Thereafter		above $0.450		50.10%	49.90%

Equity_and_Partners_Capital_ta

Equity and Partners' Capital (tables)	12 Months Ended
	Dec. 31, 2014
Partners' Capital Notes [Abstract]
Equity Offerings Table	The Partnership completed the following public offerings of its common units during 2014, 2013 and 2012:
	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
	June 2012 equity offering	5,000,000			102,041			$	43.88			$	7,468	$	216,409
	May 2013 equity offering (2)	7,015,000			143,163			61.18				13,203		424,733
	December 2013 equity offering (3)	4,800,000			97,959			61.51				9,447		291,827
	Continuous Offering Program - 2013 (4)	685,735			13,996			60.84				965		41,603
	Continuous Offering Program - 2014 (5)	1,133,384			23,132			73.48				1,738		83,245
	November 2014 equity offering (6)	8,620,153			153,061			70.85				18,583		602,999
	(1)	Represents general partner units issued to the general partner in exchange for the general partner’s proportionate capital contribution.
	(2)	Includes the issuance of 915,000 common units pursuant to the full exercise of the underwriters’ over-allotment option.
	(3)	Includes the issuance of 300,000 common units on January 3, 2014, pursuant to the partial exercise of the underwriters’ over-allotment option. Net proceeds from this partial exercise (including the general partner’s proportionate capital contribution) were $18.1 million.
	(4)	Represents common and general partner units issued during the year ended December 31, 2013, pursuant to the Partnership’s registration statement filed with the U.S. Securities and Exchange Commission (“SEC”) in August 2012 authorizing the issuance of up to an aggregate of $125.0 million of common units (the “Continuous Offering Program”). Gross proceeds generated (including the general partner’s proportionate capital contributions) during the year ended December 31, 2013, were $42.6 million. The price per unit in the table above represents an average price for all issuances under the Continuous Offering Program during 2013.
	(5)	Represents common and general partner units issued during the year ended December 31, 2014, under the Continuous Offering Program. 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 Continuous Offering Program 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.
	(6)	Includes the issuance of 1,120,153 common units pursuant to the partial exercise of the underwriters’ over-allotment option. Net proceeds from this partial exercise were $77.0 million. Beginning with this partial exercise, the Partnership’s general partner elected not to make a corresponding capital contribution to maintain the general partner’s 2.0% interest in the Partnership. See Note 3.
Limited Partner and General Partner Units Table	The following table summarizes the common, Class C and general partner units issued during the years ended December 31, 2014 and 2013:
			Common			Class C Units			General			Total
			Units						Partner Units
	Balance at December 31, 2012		104,660,553			—			2,135,930			106,796,483
	Non-Operated Marcellus Interest acquisition		449,129			—			9,166			458,295
	Long-Term Incentive Plan awards		12,395			—			253			12,648
	May 2013 equity offering		7,015,000			—			143,163			7,158,163
	Continuous Offering Program		685,735			—			13,996			699,731
	December 2013 equity offering		4,500,000			—			91,837			4,591,837
	Balance at December 31, 2013		117,322,812			—			2,394,345			119,717,157
	December 2013 equity offering		300,000			—			6,122			306,122
	Long-Term Incentive Plan awards		10,291			—			112			10,403
	TEFR Interests acquisition		308,490			—			6,296			314,786
	Continuous Offering Program		1,133,384			—			23,132			1,156,516
	November 2014 equity offering		8,620,153			—			153,061			8,773,214
	Class C unit issuance		—			10,913,853			—			10,913,853
	Balance at December 31, 2014		127,695,130			10,913,853			2,583,068			141,192,051
Calculation of Net Income Per Unit Table	The following table illustrates the Partnership’s calculation of net income per unit for common units:
		Year Ended December 31,
	thousands except per-unit amounts	2014				2013				2012
	Net income attributable to Western Gas Partners, LP	$	376,533			$	274,627			$	134,377
	Pre-acquisition net (income) loss allocated to Anadarko	956				(4,128		)		(27,391		)
	General partner interest in net (income) loss	(120,980		)		(69,633		)		(28,089		)
	Limited partners’ interest in net income	256,509				200,866				78,897
	Net income allocable to common units	254,737				200,866				78,897
	Net income allocable to Class C units	1,772				—				—
	Limited partners’ interest in net income	$	256,509			$	200,866			$	78,897
	Net income per unit
	Common units - basic	$	2.13			$	1.83			$	0.84
	Common units – diluted	2.12				1.83				0.84
	Weighted-average units outstanding
	Common units – basic	119,822				109,872				93,936
	Class C units	1,106				—				—
	Common units – diluted	120,928				109,872				93,936

Transactions_With_Affiliates_t

Transactions With Affiliates (tables)	12 Months Ended
	Dec. 31, 2014
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 December 31, 2014:
	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:
			Year Ended December 31,
	thousands		2014				2013				2012
	Gains (losses) on commodity price swap agreements related to sales: (1)
	Natural gas sales		$	9,494			$	21,382			$	37,665
	Natural gas liquids sales		113,866				102,076				66,260
	Total		123,360				123,458				103,925
	Losses on commodity price swap agreements related to purchases (2)		(68,492		)		(85,294		)		(89,710		)
	Net gains (losses) on commodity price swap agreements		$	54,868			$	38,164			$	14,215
	(1)	Reported in affiliate natural gas, natural gas liquids and 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.
LTIP Award Activity Table	The following table summarizes WES LTIP award activity for the years ended December 31, 2014, 2013 and 2012:
		2014							2013							2012
		Weighted-Average Grant-Date Fair Value				Units			Weighted-Average Grant-Date Fair Value				Units			Weighted-Average Grant-Date Fair Value			Units
	Phantom units outstanding at beginning of year	$	49.47			16,844			$	41.77			25,619			$	33.92		23,978
	Vested	49.55				(13,122	)		41.28				(14,695	)		33.2			(14,260	)
	Granted	68.14				5,800			62.49				5,920			45.91			15,901
	Phantom units outstanding at end of year	60.74				9,522			49.47				16,844			41.77			25,619
Related Party Transactions Tables	The following table summarizes the amounts the Partnership reimbursed to Anadarko:
			Year Ended December 31,
	thousands		2014				2013				2012
	General and administrative expenses		$	20,249			$	16,882			$	14,904
	Public company expenses		8,006				7,152				6,830
	Total reimbursement		$	28,255			$	24,034			$	21,734
	The following table summarizes the Partnership’s purchases from and sales to Anadarko of pipe and equipment:
			Year Ended December 31,
			2014				2013				2012				2014			2013			2012
	thousands		Purchases												Sales
	Cash consideration		$	22,943			$	11,211			$	24,705			$	—		$	85		$	760
	Net carrying value		12,210				5,309				8,009				—			38			393
	Partners’ capital adjustment		$	10,733			$	5,902			$	16,696			$	—		$	47		$	367
	The following table summarizes affiliate transactions, which include revenue from affiliates, reimbursement of operating expenses and purchases of natural gas:
			Year ended December 31,
	thousands		2014				2013				2012
	Revenues (1)		$	969,995			$	805,526			$	688,026
	Equity income, net (1)		57,836				22,948				16,042
	Cost of product (1)		114,000				129,045				145,250
	Operation and maintenance (2)		58,884				56,435				51,237
	General and administrative (3)		26,989				23,354				92,847
	Operating expenses		199,873				208,834				289,334
	Interest income (4)		16,900				16,900				16,900
	Interest expense (5)		—				—				2,766
	Distributions to unitholders (6)		234,024				169,150				98,280
	Contributions from noncontrolling interest owners (7)		—				—				12,588
	Distributions to noncontrolling interest owners (7)		—				—				6,528
	(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, WGP LTIP and Anadarko Incentive Plans, and The Incentive Plan within this Note 5).
	(4)	Represents interest income recognized on the note receivable from Anadarko.
	(5)	For the year ended December 31, 2012, includes interest expense recognized on the note payable to Anadarko (see Note 12) and interest imputed on the reimbursement payable to Anadarko for certain expenditures Anadarko incurred in 2011 related to the construction of the Brasada complex and Lancaster plant. The Partnership repaid the note payable to Anadarko in June 2012, and repaid the reimbursement payable to Anadarko associated with the construction of the Brasada complex and Lancaster plant in the fourth quarter of 2012.
	(6)	Represents distributions paid under the partnership agreement (see Note 3 and Note 4).
	(7)	As described in Note 2, the Partnership acquired the additional Chipeta interest on August 1, 2012, and accounted for the acquisition on a prospective basis. As such, contributions from noncontrolling interest owners and distributions to noncontrolling interest owners subsequent to the acquisition date no longer reflect contributions from or distributions to Anadarko.

Income_Taxes_tables

Income Taxes (tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Components of Income Tax Expense (Benefit) Table	The components of the Partnership’s income tax expense (benefit) are as follows:
		Year Ended December 31,
	thousands	2014			2013			2012
	Current income tax expense (benefit)
	Federal income tax expense (benefit)	$	(625	)	$	(30,176	)	$	(7,576	)
	State income tax expense (benefit)	69			640			(1,843		)
	Total current income tax expense (benefit)	(556		)	(29,536		)	(9,419		)
	Deferred income tax expense (benefit)
	Federal income tax expense (benefit)	171			32,930			22,324
	State income tax expense (benefit)	2,412			(1,039		)	7,785
	Total deferred income tax expense (benefit)	2,583			31,891			30,109
	Total income tax expense	$	2,027		$	2,355		$	20,690
Tax Rate Reconciliation Table	Total income taxes differed from the amounts computed by applying the statutory income tax rate to income before income taxes. The sources of these differences are as follows:
		Year Ended December 31,
	thousands except percentages	2014			2013			2012
	Income before income taxes	$	392,585		$	287,798		$	169,957
	Statutory tax rate	—		%	—		%	—		%
	Tax computed at statutory rate	$	—		$	—		$	—
	Adjustments resulting from:
	Federal taxes on income attributable to Partnership assets pre-acquisition	(454		)	3,090			17,226
	State taxes on income attributable to Partnership assets pre-acquisition (net of federal benefit)	—			624			2,206
	Texas margin tax expense (benefit)	2,481			(1,359		)	1,258
	Income tax expense	$	2,027		$	2,355		$	20,690
	Effective tax rate	1		%	1		%	12		%
Income Tax Temporary Differences Table	The tax effects of temporary differences that give rise to significant portions of deferred tax assets (liabilities) are as follows:
		December 31,
	thousands	2014			2013
	Credit carryforwards	$	14		$	14
	Net current deferred income tax assets	14			14
	Depreciable property	(3,240		)	(38,528		)
	Credit carryforwards	512			527
	Other intangible assets	(1,450		)	—
	Other	7			3
	Net long-term deferred income tax liabilities	(4,171		)	(37,998		)
	Total net deferred income tax liabilities	$	(4,157	)	$	(37,984	)

Property_Plant_and_Equipment_t

Property, Plant and Equipment (table)	12 Months Ended
	Dec. 31, 2014
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:
			December 31,
	thousands	Estimated Useful Life	2014		2013
	Land	n/a	$	2,839	$	2,584
	Gathering systems	3 to 47 years	4,790,974		3,673,008
	Pipelines and equipment	15 to 45 years	151,107		146,008
	Assets under construction	n/a	464,507		405,633
	Other	3 to 40 years	15,272		11,867
	Total property, plant and equipment		5,424,699		4,239,100
	Accumulated depreciation		1,040,328		855,845
	Net property, plant and equipment		$	4,384,371	$	3,383,255

Goodwill_and_Intangibles_table

Goodwill and Intangibles (tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Other Intangible Assets Table	The following table presents the gross carrying amount and accumulated amortization of other intangible assets:
		December 31,
	thousands	2014			2013
	Gross carrying amount	$	892,555		$	56,988
	Accumulated amortization	(7,698		)	(3,382		)
	Other intangible assets	$	884,857		$	53,606

Equity_Investments_tables

Equity Investments (tables)	12 Months Ended
	Dec. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]
Equity Investments Table	The following table presents the activity in the Partnership’s equity investments for the years ended December 31, 2014 and 2013:
		Equity Investments
	thousands	Fort			White			Rendezvous (3)			Mont			TEG (5)			TEP (6)			FRP (7)			Total
		Union (1)			Cliffs (2)						Belvieu JV (4)
	Balance at December 31, 2012	$	23,453		$	17,567		$	65,110		$	—		$	9,033		$	80,737		$	23,866		$	219,766
	Initial investment	—			—			—			78,129			—			—			—			78,129
	Investment earnings (loss), net of amortization	6,273			9,681			2,088			5,690			93			(776		)	(101		)	22,948
	Contributions	16			19,087			—			37,309			6,732			108,969			105,547			277,660
	Capitalized interest	—			—			—			1,352			791			8,801			6,089			17,033
	Distributions	(4,570		)	(9,099		)	(4,029		)	—			—			—			—			(17,698		)
	Distributions in excess of cumulative earnings (8)	—			(2,197		)	(2,241		)	—			—			—			—			(4,438		)
	Balance at December 31, 2013	$	25,172		$	35,039		$	60,928		$	122,480		$	16,649		$	197,731		$	135,401		$	593,400
	Investment earnings (loss), net of amortization	6,344			11,912			1,729			29,029			650			6,108			2,064			57,836
	Contributions	—			10,456			—			3,957			352			6,623			42,033			63,421
	Capitalized interest	—			—			—			—			—			—			857			857
	Distributions	(5,583		)	(11,330		)	(3,669		)	(34,129		)	(523		)	(5,622		)	(2,111		)	(62,967		)
	Distributions in excess of cumulative earnings (8)	—			(1,762		)	(2,652		)	—			(338		)	(6,047		)	(7,256		)	(18,055		)
	Balance at December 31, 2014	$	25,933		$	44,315		$	56,336		$	121,337		$	16,790		$	198,793		$	170,988		$	634,492
	(1)	The Partnership has a 14.81% interest in Fort Union, a joint venture that owns a gathering pipeline and treating facilities in the Powder River Basin. Anadarko is the construction manager and physical operator of the Fort Union facilities. Certain business decisions, including, but not limited to, decisions with respect to significant expenditures or contractual commitments, annual budgets, material financings, dispositions of assets or amending the owners’ firm gathering agreements, require 65% or unanimous approval of the owners.
	(2)	The Partnership has a 10% interest in White Cliffs, a limited liability company that owns a crude oil pipeline that originates in Platteville, Colorado and terminates in Cushing, Oklahoma. The third-party majority owner is the manager of the White Cliffs operations. Certain business decisions, including, but not limited to, approval of annual budgets and decisions with respect to significant expenditures, contractual commitments, acquisitions, material financings, dispositions of assets or admitting new members, require more than 75% approval of the members.
	(3)	The Partnership has a 22% interest in Rendezvous, a limited liability company that operates gas gathering facilities in Southwestern Wyoming. Certain business decisions, including, but not limited to, decisions with respect to significant expenditures or contractual commitments, annual budgets, material financings, dispositions of assets or amending the members’ gas servicing agreements, require unanimous approval of the members.
	(4)	The Partnership has a 25% interest in the Mont Belvieu JV, an entity formed to design, construct, and own two fractionation trains located in Mont Belvieu, Texas. A third party is the operator of the Mont Belvieu JV fractionation trains. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the creation, appointment, or removal of officer positions require 50% or unanimous approval of the owners.
	(5)	The Partnership has a 20% interest in TEG, an entity that consists of two NGL gathering systems that link natural gas processing plants to TEP. Enbridge Midcoast Energy, LP (“Enbridge”) is the operator of the two gathering systems. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the delegation, creation, appointment, or removal of officer positions require more than 50% approval of the members.
	(6)	The Partnership has a 20% interest in TEP, which consists of an NGL pipeline that originates in Skellytown, Texas and extends to Mont Belvieu, Texas. Enterprise Products Operating LLC (“Enterprise”) is the operator of TEP. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the creation, appointment, or removal of officer positions require more than 50% approval of the members.
	(7)	The Partnership has a 33.33% interest in the FRP, an NGL pipeline that extends from Weld County, Colorado to Skellytown, Texas. Enterprise is the operator of FRP. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the creation, appointment, or removal of officer positions require more than 50% approval of the members.
	(8)	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.
Summarized Statements of Equity Investments Affiliates Presented at 100 Percent	The following tables present the summarized combined financial information for the Partnership’s equity investments (amounts represent 100% of investee financial information):
			Year Ended December 31,
	thousands		2014			2013			2012
	Consolidated Statements of Income
	Revenues		$	548,629		$	261,705		$	199,764
	Operating income		336,188			171,496			135,498
	Net income		333,705			170,175			133,987
			December 31,
	thousands		2014			2013
	Consolidated Balance Sheets
	Current assets		$	141,781		$	186,690
	Property, plant and equipment, net		2,814,336			2,676,531
	Other assets		48,799			38,258
	Total assets		$	3,004,916		$	2,901,479
	Current liabilities		95,102			206,602
	Non-current liabilities		22,615			34,012
	Equity		2,887,199			2,660,865
	Total liabilities and equity		$	3,004,916		$	2,901,479

Components_of_Working_Capital_

Components of Working Capital (tables)	12 Months Ended
	Dec. 31, 2014
Components Of Working Capital [Abstract]
Other Current Assets Table	A summary of other current assets is as follows:
		December 31,
	thousands	2014		2013
	Natural gas liquids inventory	$	5,316	$	2,584
	Natural gas imbalance receivables	415		3,605
	Prepaid insurance	2,443		2,123
	Other	1,893		1,710
	Total other current assets	$	10,067	$	10,022
Accrued Liabilities Table	A summary of accrued liabilities is as follows:
		December 31,
	thousands	2014		2013
	Accrued capital expenditures	$	116,891	$	94,750
	Accrued plant purchases	14,023		21,396
	Accrued interest expense	24,741		18,119
	Short-term asset retirement obligations	1,212		1,966
	Short-term remediation and reclamation obligations	475		562
	Income taxes payable	207		—
	Other	1,106		218
	Total accrued liabilities	$	158,655	$	137,011

Asset_Retirement_Obligations_t

Asset Retirement Obligations (table)	12 Months Ended
	Dec. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations Table	The following table provides a summary of changes in asset retirement obligations:
		Year Ended December 31,
	thousands	2014			2013
	Carrying amount of asset retirement obligations at beginning of year	$	78,035		$	66,723
	Liabilities incurred	13,769			14,143
	Liabilities settled	(4,181		)	(1,943		)
	Accretion expense	4,846			4,326
	Revisions in estimated liabilities	16,623			(5,214		)
	Carrying amount of asset retirement obligations at end of year	$	109,092		$	78,035

Debt_and_Interest_Expense_tabl

Debt and Interest Expense (tables)	12 Months Ended
	Dec. 31, 2014
Debt Instruments [Abstract]
Debt Outstanding and Debt Activity Tables	The following table presents the Partnership’s outstanding debt as of December 31, 2014 and 2013:
			December 31, 2014									31-Dec-13
	thousands		Principal			Carrying			Fair			Principal		Carrying		Fair
						Value			Value (1)					Value		Value (1)
	5.375% Senior Notes due 2021		$	500,000		$	495,714		$	549,530		$	500,000	$	495,173	$	533,615
	4.000% Senior Notes due 2022		670,000			672,930			681,942			670,000		673,278		641,237
	Revolving credit facility		510,000			510,000			510,000			—		—		—
	2.600% Senior Notes due 2018		350,000			350,474			352,162			250,000		249,718		247,988
	5.450% Senior Notes due 2044		400,000			393,836			417,619			—		—		—
	Total long-term debt		$	2,430,000		$	2,422,954		$	2,511,253		$	1,420,000	$	1,418,169	$	1,422,840
	(1)	Fair value is measured using Level 2 inputs.
	Debt activity. The following table presents the debt activity of the Partnership for the years ended December 31, 2014 and 2013:
	thousands		Carrying Value
	Balance at December 31, 2012		$	1,168,278
	Revolving credit facility borrowings		710,000
	Repayments of revolving credit facility		(710,000		)
	Issuance of 2.600% Senior Notes due 2018		250,000
	Other		(109		)
	Balance at December 31, 2013		$	1,418,169
	Revolving credit facility borrowings		1,160,000
	Issuance of 5.450% Senior Notes due 2044		400,000
	Issuance of 2.600% Senior Notes due 2018		100,000
	Repayments of revolving credit facility		(650,000		)
	Other		(5,215		)
	Balance at December 31, 2014		$	2,422,954
Interest Expense Table	The following table summarizes the amounts included in interest expense:
			Year Ended December 31,
	thousands		2014			2013			2012
	Third parties
	Interest expense on long-term debt		$	81,495		$	59,293		$	41,171
	Amortization of debt issuance costs and commitment fees		5,103			4,449			4,319
	Capitalized interest		(9,832		)	(11,945		)	(6,196		)
	Total interest expense – third parties		76,766			51,797			39,294
	Affiliates
	Interest expense on note payable to Anadarko (1)		—			—			2,440
	Interest expense on affiliate balances (2)		—			—			326
	Total interest expense – affiliates		—			—			2,766
	Interest expense		$	76,766		$	51,797		$	42,060
	(1)	In June 2012, the note payable to Anadarko was repaid in full. See Note payable to Anadarko within this Note 12.
	(2)	Imputed interest expense on the reimbursement payable to Anadarko for certain expenditures Anadarko incurred in 2011 related to the construction of the Brasada complex and Lancaster plant. In the fourth quarter of 2012, the Partnership repaid the reimbursement payable to Anadarko associated with the construction of the Brasada complex and Lancaster plant.

Commitments_and_Contingencies_

Commitments and Contingencies (table)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies [Abstract]
Operating Lease Obligations Table	The amounts in the table below represent existing contractual operating lease obligations as of December 31, 2014, that may be assigned or otherwise charged to the Partnership pursuant to the reimbursement provisions of the omnibus agreement:
	thousands	Operating Leases
	2015	$	338
	2016	303
	2017	157
	2018	34
	2019	—
	Thereafter	—
	Total	$	832

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Asset Table (details)	Dec. 31, 2014
	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 Pipeline [Member]
Assets [Line Items]
Assets, number of units	1
Operated Interests [Member] | Natural Gas Gathering Systems [Member]
Assets [Line Items]
Assets, number of units	1
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 Pipeline [Member]
Assets [Line Items]
Assets, number of units	1

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Additional Information (details) (USD $)

1 Months Ended

12 Months Ended

0 Months Ended

1 Months Ended

0 Months Ended

1 Months Ended

Nov. 30, 2014

Dec. 31, 2014

Dec. 31, 2012

Mar. 01, 2013

Mar. 08, 2013

Dec. 31, 2008

Aug. 01, 2012

Jul. 31, 2009

Dec. 31, 2013

31-May-13

Jun. 30, 2012

Price per unit

$70.85

[1]

$61.51

[2]

$61.18

[3]

$43.88

General partner's interest

2.00%

Natural gas imbalance receivables

415,000

$3,605,000

Natural gas imbalance payables

700,000

2,500,000

Western Gas Partners Long Term Incentive Plan [Member]

Units authorized under LTIP

2,250,000

Units available under LTIP

2,133,227

Western Gas Equity Partners [Member]

Common units issued

19,758,150

Price per unit

$22

Proceeds from the issuance of units

$409,400,000

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%

33.75%

[4]

Anadarko-Operated Marcellus Interest [Member]

Percentage acquired

33.75%

33.75%

[5]

Newcastle [Member]

Percentage acquired

50.00%

50.00%

Chipeta Processing Limited Liability Company [Member]

Percentage acquired

75.00%

24.00%

[6]

51.00%

Ownership interest by noncontrolling owner

25.00%

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]

Includes the issuance of 1,120,153 common units pursuant to the partial exercise of the underwriters’ over-allotment option. Net proceeds from this partial exercise were $77.0 million. Beginning with this partial exercise, the Partnership’s general partner elected not to make a corresponding capital contribution to maintain the general partner’s 2.0% interest in the Partnership. See Note 3.

[2]

Includes the issuance of 300,000 common units on January 3, 2014, pursuant to the partial exercise of the underwriters’ over-allotment option. Net proceeds from this partial exercise (including the general partner’s proportionate capital contribution) were $18.1 million.

[3]

Includes the issuance of 915,000 common units pursuant to the full exercise of the underwriters’ over-allotment option.

[4]

The Partnership acquired Anadarko’s 33.75% interest (non-operated) (the “Non-Operated Marcellus Interest”) in the Liberty and Rome gas gathering systems (the “Non-Operated Marcellus Interest systems”), serving production from the Marcellus shale in North-central Pennsylvania. In connection with the issuance of the common units, the Partnership’s general partner purchased 9,166 general partner units for consideration of $0.5 million.

[5]

The Partnership acquired a 33.75% interest (the “Anadarko-Operated Marcellus Interest”) in each of the Larry’s Creek, Seely and Warrensville gas gathering systems (the “Anadarko-Operated Marcellus Interest systems”), which are operated by Anadarko and serve production from the Marcellus shale in North-central Pennsylvania, from a third party. During the third quarter of 2013, the Partnership recorded a $1.1 million decrease in the assets acquired and liabilities assumed in the acquisition, representing the final purchase price allocation.

[6]

The Partnership acquired Anadarko’s additional Chipeta interest (as described in Note 1). The Partnership received distributions related to the additional interest beginning July 1, 2012. This transaction brought the Partnership’s total membership interest in Chipeta to 75%. The remaining 25% membership interest in Chipeta held by a third-party member is reflected as noncontrolling interests in the consolidated financial statements for all periods presented.

Acquisitions_Acquisitions_Tabl

Acquisitions - Acquisitions Table (details) (USD $)

12 Months Ended

0 Months Ended

1 Months Ended

0 Months Ended

In Thousands, except Share data, unless otherwise specified

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Jan. 13, 2012

Aug. 01, 2012

Jul. 31, 2009

Mar. 01, 2013

Mar. 08, 2013

Jun. 05, 2013

Sep. 03, 2013

Mar. 03, 2014

Nov. 25, 2014

Business Acquisition [Line Items]

Borrowings

$1,646,878

$957,503

$1,041,648

Cash on hand

78,129

Table Text Block Supplement [Abstract]

General partner units issued

2,583,068

2,394,345

Mountain Gas Resources [Member]

Business Acquisition [Line Items]

Percentage acquired

100.00%

[1]

Borrowings

299,000

[1]

Cash on hand

159,587

[1]

Mountain Gas Resources [Member] | Rendezvous [Member]

Business Acquisition [Line Items]

Equity investment ownership

22.00%

Chipeta Processing Limited Liability Company [Member]

Business Acquisition [Line Items]

Percentage acquired

75.00%

24.00%

[2]

51.00%

Cash on hand

128,250

[2]

Table Text Block Supplement [Abstract]

Ownership interest by noncontrolling owner

25.00%

Non-Operated Marcellus Interest [Member]

Business Acquisition [Line Items]

Percentage acquired

33.75%

33.75%

[3]

Borrowings

250,000

[3]

Cash on hand

215,500

[3]

Table Text Block Supplement [Abstract]

General partner units issued

9,166

Anadarko-Operated Marcellus Interest [Member]

Business Acquisition [Line Items]

Percentage acquired

33.75%

33.75%

[4]

Borrowings

133,500

[4]

Table Text Block Supplement [Abstract]

Purchase price adjustment

1,100

Mont Belvieu Joint Venture [Member]

Business Acquisition [Line Items]

Equity investment ownership

25.00%

[5]

Cash on hand

78,129

[5]

Mont Belvieu Joint Venture [Member] | Fractionation Train [Member]

Table Text Block Supplement [Abstract]

Assets, number of units

2

Overland Trail Transmission Limited Liability Company [Member]

Business Acquisition [Line Items]

Percentage acquired

100.00%

[6]

Borrowings

27,500

[6]

Texas Express And Front Range [Member]

Business Acquisition [Line Items]

Borrowings

350,000

[7]

Cash on hand

6,250

[7]

Table Text Block Supplement [Abstract]

General partner units issued

6,296

Texas Express Gathering Limited Liability Company [Member]

Business Acquisition [Line Items]

Equity investment ownership

20.00%

Texas Express Pipeline Limited Liability Company [Member]

Business Acquisition [Line Items]

Equity investment ownership

20.00%

Front Range Pipeline Limited Liability Company [Member]

Business Acquisition [Line Items]

Equity investment ownership

33.33%

Delaware Basin Midstream Limited Liability Company [Member]

Business Acquisition [Line Items]

Percentage acquired

100.00%

[8]

Borrowings

475,000

[8]

Cash on hand

298,327

[8]

Table Text Block Supplement [Abstract]

Purchase price adjustment

1,553,959

Common Units [Member] | Mountain Gas Resources [Member]

Business Acquisition [Line Items]

Units issued

632,783

[1]

Common Units [Member] | Chipeta Processing Limited Liability Company [Member]

Business Acquisition [Line Items]

Units issued

151,235

[2]

Common Units [Member] | Non-Operated Marcellus Interest [Member]

Business Acquisition [Line Items]

Units issued

449,129

[3]

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

Business Acquisition [Line Items]

Units issued

308,490

[7]

Class C Units [Member]

Business Acquisition [Line Items]

Class C units issued

10,913,853

Table Text Block Supplement [Abstract]

Proceeds from the issuance of units

750,000

0

0

750,000

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

Business Acquisition [Line Items]

Class C units issued

10,913,853

[8]

General Partner [Member] | Mountain Gas Resources [Member]

Business Acquisition [Line Items]

Units issued

12,914

[1]

General Partner [Member] | Chipeta Processing Limited Liability Company [Member]

Business Acquisition [Line Items]

Units issued

3,086

[2]

General Partner [Member] | Non-Operated Marcellus Interest [Member]

Table Text Block Supplement [Abstract]

Proceeds from the issuance of units

500

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

Table Text Block Supplement [Abstract]

Proceeds from the issuance of units

$400

[1]

The assets acquired from Anadarko consisted of (i) the “Red Desert complex,” which is located in the greater Green River Basin in southwestern Wyoming, and includes the Patrick Draw processing plant, the Red Desert processing plant, gathering lines, and related facilities, (ii) a 22% interest in Rendezvous, which owns a gathering system serving the Jonah and Pinedale Anticline fields in southwestern Wyoming, and (iii) certain additional midstream assets and equipment. These assets are collectively referred to as the “MGR assets” and the acquisition as the “MGR acquisition.”

[2]

The Partnership acquired Anadarko’s additional Chipeta interest (as described in Note 1). The Partnership received distributions related to the additional interest beginning July 1, 2012. This transaction brought the Partnership’s total membership interest in Chipeta to 75%. The remaining 25% membership interest in Chipeta held by a third-party member is reflected as noncontrolling interests in the consolidated financial statements for all periods presented.

[3]

The Partnership acquired Anadarko’s 33.75% interest (non-operated) (the “Non-Operated Marcellus Interest”) in the Liberty and Rome gas gathering systems (the “Non-Operated Marcellus Interest systems”), serving production from the Marcellus shale in North-central Pennsylvania. In connection with the issuance of the common units, the Partnership’s general partner purchased 9,166 general partner units for consideration of $0.5 million.

[4]

The Partnership acquired a 33.75% interest (the “Anadarko-Operated Marcellus Interest”) in each of the Larry’s Creek, Seely and Warrensville gas gathering systems (the “Anadarko-Operated Marcellus Interest systems”), which are operated by Anadarko and serve production from the Marcellus shale in North-central Pennsylvania, from a third party. During the third quarter of 2013, the Partnership recorded a $1.1 million decrease in the assets acquired and liabilities assumed in the acquisition, representing the final purchase price allocation.

[5]

The Partnership acquired a 25% interest in the Mont Belvieu JV, an entity formed to design, construct, and own two fractionation trains located in Mont Belvieu, Texas, from a third party. The interest acquired is accounted for under the equity method of accounting.

[6]

The Partnership acquired Overland Trail Transmission, LLC (“OTTCO”), a Delaware limited liability company, from a third party. OTTCO owns and operates an intrastate pipeline that connects the Partnership’s Red Desert and Granger complexes in southwestern Wyoming.

[7]

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.

[8]

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 serve production from Reeves, Loving and Culberson Counties, Texas and Eddy and Lea Counties, New Mexico. These assets are referred to collectively as the “DBM complex.” See Note 4 for a discussion of the Class C units.

Acquisitions_Purchase_Price_Al

Acquisitions - Purchase Price Allocation Table (details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Business Acquisition [Line Items]
Goodwill	$384,387	$105,336
Delaware Basin Midstream Limited Liability Company [Member]
Business Acquisition [Line Items]
Current assets	46,358
Property, plant and equipment	440,971
Goodwill	279,051
Other intangible assets	835,566
Accounts payables	-13,064
Accrued liabilities	-24,824
Deferred income taxes	-1,450
Asset retirement obligations and other	-8,649
Total purchase price	$1,553,959

Acquisitions_Pro_Forma_Condens

Acquisitions - Pro Forma Condensed Financial Information Table (details) (Delaware Basin Midstream Limited Liability Company [Member], USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Delaware Basin Midstream Limited Liability Company [Member]
Business Acquisition [Line Items]
Revenues	$1,397,030	$1,107,030
Net income	332,420	239,382
Net income attributable to Western Gas Partners, LP	$318,395	$228,566
Net income per common unit - basic and diluted	$1.34	$1.12

Acquisitions_Additional_Inform

Acquisitions - Additional Information (details) (USD $)	12 Months Ended			1 Months Ended	0 Months Ended		1 Months Ended	0 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2008	Aug. 01, 2012		Jul. 31, 2009	Nov. 25, 2014		Sep. 30, 2010
Business Acquisition [Line Items]
Revenues	$1,273,763	$1,029,763	$894,476
Operating expenses	880,012	731,853	715,693
Newcastle [Member]
Business Acquisition [Line Items]
Percentage acquired	50.00%			50.00%
Fort Union [Member]
Business Acquisition [Line Items]
Equity investment ownership				14.81%
Chipeta Processing Limited Liability Company [Member]
Business Acquisition [Line Items]
Percentage acquired	75.00%				24.00%	[1]	51.00%
White Cliffs [Member]
Business Acquisition [Line Items]
Equity investment ownership										10.00%
Delaware Basin Midstream Limited Liability Company [Member]
Business Acquisition [Line Items]
Percentage acquired								100.00%	[2]
Revenues	12,500
Operating expenses	$10,400
[1]	The Partnership acquired Anadarko’s additional Chipeta interest (as described in Note 1). The Partnership received distributions related to the additional interest beginning July 1, 2012. This transaction brought the Partnership’s total membership interest in Chipeta to 75%. The remaining 25% membership interest in Chipeta held by a third-party member is reflected as noncontrolling interests in the consolidated financial statements for all periods presented.
[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 serve production from Reeves, Loving and Culberson Counties, Texas and Eddy and Lea Counties, New Mexico. These assets are referred to collectively as the “DBM complex.” See Note 4 for a discussion of the Class C units.

Partnership_Distributions_Cash

Partnership Distributions - Cash Distributions Table (details) (USD $)	1 Months Ended	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	31-May-08	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012
Distributions Made to Members or Limited Partners [Abstract]
Total quarterly distribution per unit	$0.30	$0.70	[1]	$0.68	$0.65	$0.63	$0.60	$0.58	$0.56	$0.54	$0.52	$0.50	$0.48	$0.46
Total quarterly cash distribution		$126,044	[1]	$111,608	$105,655	$98,749	$92,609	$83,986	$79,315	$70,143	$65,657	$56,346	$52,425	$46,053
[1]	On January 22, 2015, the Board of Directors of the Partnership’s general partner declared a cash distribution to the Partnership’s unitholders of $0.700 per unit, or $126.0 million in aggregate, including incentive distributions, but excluding distributions on Class C units (see Class C unit distributions below). The cash distribution was paid on February 12, 2015, to unitholders of record at the close of business on February 2, 2015.

Partnership_Distributions_Ince

Partnership Distributions - Incentive Distribution Rights Table (details) (USD $)

1 Months Ended

3 Months Ended

31-May-08

Dec. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Total quarterly distribution per unit

$0.30

$0.70

[1]

$0.68

$0.65

$0.63

$0.60

$0.58

$0.56

$0.54

$0.52

$0.50

$0.48

$0.46

Marginal percentage interest in distributions

1.90%

Unitholders [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Marginal percentage interest in distributions

98.10%

Unitholders [Member] | First Target Distribution [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Marginal percentage interest in distributions

98.10%

Unitholders [Member] | Second Target Distribution [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Marginal percentage interest in distributions

85.10%

Unitholders [Member] | Third Target Distribution [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Marginal percentage interest in distributions

75.10%

Unitholders [Member] | Thereafter [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Marginal percentage interest in distributions

50.10%

General Partner [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Marginal percentage interest in distributions

1.90%

General Partner [Member] | First Target Distribution [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Marginal percentage interest in distributions

1.90%

General Partner [Member] | Second Target Distribution [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Marginal percentage interest in distributions

14.90%

General Partner [Member] | Third Target Distribution [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Marginal percentage interest in distributions

24.90%

General Partner [Member] | Thereafter [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Marginal percentage interest in distributions

49.90%

Minimum [Member] | First Target Distribution [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Total quarterly distribution per unit

$0.30

Minimum [Member] | Second Target Distribution [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Total quarterly distribution per unit

$0.35

Minimum [Member] | Third Target Distribution [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Total quarterly distribution per unit

$0.38

Maximum [Member] | First Target Distribution [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Total quarterly distribution per unit

$0.35

Maximum [Member] | Second Target Distribution [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Total quarterly distribution per unit

$0.38

Maximum [Member] | Third Target Distribution [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Total quarterly distribution per unit

$0.45

Maximum [Member] | Thereafter [Member]

Incentive Distribution Made to Managing Member or General Partner [Line Items]

Total quarterly distribution per unit

$0.45

[1]

On January 22, 2015, the Board of Directors of the Partnership’s general partner declared a cash distribution to the Partnership’s unitholders of $0.700 per unit, or $126.0 million in aggregate, including incentive distributions, but excluding distributions on Class C units (see Class C unit distributions below). The cash distribution was paid on February 12, 2015, to unitholders of record at the close of business on February 2, 2015.

Partnership_Distributions_Addi

Partnership Distributions - Additional Information (details) (USD $)	12 Months Ended	0 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Nov. 25, 2014	Feb. 12, 2015	31-May-08
Distribution Made to Limited Partner [Line Items]
Partnership agreement day requirement of distribution of available cash	45 days
Marginal percentage interest in distributions	1.90%
Class C Units [Member]
Distribution Made to Limited Partner [Line Items]
Discount rate percentage		6.00%
Fair value paid in kind (PIK) C distributions	3.1
Class C Units [Member] | Subsequent Event [Member]
Distribution Made to Limited Partner [Line Items]
PIK C unit distribution			45,711
Incentive Distribution Rights [Member] | Maximum [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions				48.00%

Equity_and_Partners_Capital_Eq

Equity and Partners' Capital - Equity Offerings Table (details) (USD $)

1 Months Ended

0 Months Ended

12 Months Ended

Nov. 30, 2014

Dec. 31, 2013

31-May-13

Jun. 30, 2012

Jan. 03, 2014

Dec. 31, 2014

Dec. 31, 2013

Aug. 31, 2012

Capital Unit [Line Items]

Price per unit

$70.85

[1]

$61.51

[2]

$61.18

[3]

$43.88

$61.51

[2]

Underwriting discount and other offering expenses

$18,583,000

[1]

$9,447,000

[2]

$13,203,000

[3]

$7,468,000

$9,447,000

[2]

Net proceeds

602,999,000

[1]

291,827,000

[2]

424,733,000

[3]

216,409,000

Table Text Block Supplement [Abstract]

General partner's interest

2.00%

Option On Securities [Member]

Capital Unit [Line Items]

Net proceeds

77,000,000

18,100,000

Common Units [Member]

Capital Unit [Line Items]

Common units issued

8,620,153

[1]

4,800,000

[2]

7,015,000

[3]

5,000,000

8,620,153

Common Units [Member] | Option On Securities [Member]

Capital Unit [Line Items]

Common units issued

1,120,153

915,000

300,000

General Partner [Member]

Capital Unit [Line Items]

General partner units issued

153,061

[1],[4]

97,959

[2],[4]

143,163

[3],[4]

102,041

[4]

153,061

Continuous Offering Program [Member]

Capital Unit [Line Items]

General partner units issued

1,156,516

699,731

Average price per unit

73.48

[5]

$60.84

[6]

Underwriting discount and other offering expenses

965,000

[6]

1,738,000

[5]

965,000

[6]

Net proceeds

83,245,000

[5]

41,603,000

[6]

Table Text Block Supplement [Abstract]

Maximum aggregate principal of common stock

125,000,000

Gross proceeds

85,000,000

$42,600,000

Continuous Offering Program [Member] | Common Units [Member]

Capital Unit [Line Items]

Common units issued

1,133,384

[5]

685,735

[6]

Continuous Offering Program [Member] | General Partner [Member]

Capital Unit [Line Items]

General partner units issued

23,132

[4],[5]

13,996

[4],[6]

[1]

Includes the issuance of 1,120,153 common units pursuant to the partial exercise of the underwriters’ over-allotment option. Net proceeds from this partial exercise were $77.0 million. Beginning with this partial exercise, the Partnership’s general partner elected not to make a corresponding capital contribution to maintain the general partner’s 2.0% interest in the Partnership. See Note 3.

[2]

Includes the issuance of 300,000 common units on January 3, 2014, pursuant to the partial exercise of the underwriters’ over-allotment option. Net proceeds from this partial exercise (including the general partner’s proportionate capital contribution) were $18.1 million.

[3]

Includes the issuance of 915,000 common units pursuant to the full exercise of the underwriters’ over-allotment option.

[4]

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

[5]

Represents common and general partner units issued during the year ended December 31, 2014, under the Continuous Offering Program. 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 Continuous Offering Program 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.

[6]

Represents common and general partner units issued during the year ended December 31, 2013, pursuant to the Partnership’s registration statement filed with the U.S. Securities and Exchange Commission (“SEC”) in August 2012 authorizing the issuance of up to an aggregate of $125.0 million of common units (the “Continuous Offering Program”). Gross proceeds generated (including the general partner’s proportionate capital contributions) during the year ended December 31, 2013, were $42.6 million. The price per unit in the table above represents an average price for all issuances under the Continuous Offering Program during 2013.

Equity_and_Partners_Capital_Li

Equity and Partners' Capital - Limited Partner and General Partner Units (details)

12 Months Ended

1 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Nov. 30, 2014

Dec. 31, 2013

31-May-13

Jun. 30, 2012

Dec. 31, 2012

Capital Unit [Line Items]

Balance

119,717,157

106,796,483

Long-term incentive plan awards

10,403

12,648

Balance

141,192,051

119,717,157

119,717,157

Non-Operated Marcellus Interest [Member]

Capital Unit [Line Items]

Acquisition

458,295

May 2013 Equity Offering [Member]

Capital Unit [Line Items]

Offering

7,158,163

Continuous Offering Program [Member]

Capital Unit [Line Items]

Offering

1,156,516

699,731

December 2013 Equity Offering [Member]

Capital Unit [Line Items]

Offering

306,122

4,591,837

Texas Express And Front Range [Member]

Capital Unit [Line Items]

Acquisition

314,786

November 2014 Equity Offering [Member]

Capital Unit [Line Items]

Offering

8,773,214

Common Units [Member]

Capital Unit [Line Items]

Balance

117,322,812

104,660,553

Common units issued

8,620,153

8,620,153

[1]

4,800,000

[2]

7,015,000

[3]

5,000,000

Long-term incentive plan awards

10,291

12,395

Balance

127,695,130

117,322,812

117,322,812

Common Units [Member] | Non-Operated Marcellus Interest [Member]

Capital Unit [Line Items]

Acquisition

449,129

Common Units [Member] | May 2013 Equity Offering [Member]

Capital Unit [Line Items]

Common units issued

7,015,000

Common Units [Member] | Continuous Offering Program [Member]

Capital Unit [Line Items]

Common units issued

1,133,384

[4]

685,735

[5]

Common Units [Member] | December 2013 Equity Offering [Member]

Capital Unit [Line Items]

Common units issued

300,000

4,500,000

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

Capital Unit [Line Items]

Acquisition

308,490

General Partner [Member]

Capital Unit [Line Items]

Balance

2,394,345

2,135,930

Offering

153,061

153,061

[1],[6]

97,959

[2],[6]

143,163

[3],[6]

102,041

[6]

Long-term incentive plan awards

112

253

Balance

2,583,068

2,394,345

2,394,345

General Partner [Member] | Non-Operated Marcellus Interest [Member]

Capital Unit [Line Items]

Acquisition

9,166

General Partner [Member] | May 2013 Equity Offering [Member]

Capital Unit [Line Items]

Offering

143,163

General Partner [Member] | Continuous Offering Program [Member]

Capital Unit [Line Items]

Offering

23,132

[4],[6]

13,996

[5],[6]

General Partner [Member] | December 2013 Equity Offering [Member]

Capital Unit [Line Items]

Offering

6,122

91,837

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

Capital Unit [Line Items]

Acquisition

6,296

Class C Units [Member]

Capital Unit [Line Items]

Balance

0

0

Class C units issuance

10,913,853

Balance

10,913,853

0

[1]

Includes the issuance of 1,120,153 common units pursuant to the partial exercise of the underwriters’ over-allotment option. Net proceeds from this partial exercise were $77.0 million. Beginning with this partial exercise, the Partnership’s general partner elected not to make a corresponding capital contribution to maintain the general partner’s 2.0% interest in the Partnership. See Note 3.

[2]

Includes the issuance of 300,000 common units on January 3, 2014, pursuant to the partial exercise of the underwriters’ over-allotment option. Net proceeds from this partial exercise (including the general partner’s proportionate capital contribution) were $18.1 million.

[3]

Includes the issuance of 915,000 common units pursuant to the full exercise of the underwriters’ over-allotment option.

[4]

Represents common and general partner units issued during the year ended December 31, 2014, under the Continuous Offering Program. 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 Continuous Offering Program 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.

[5]

Represents common and general partner units issued during the year ended December 31, 2013, pursuant to the Partnership’s registration statement filed with the U.S. Securities and Exchange Commission (“SEC”) in August 2012 authorizing the issuance of up to an aggregate of $125.0 million of common units (the “Continuous Offering Program”). Gross proceeds generated (including the general partner’s proportionate capital contributions) during the year ended December 31, 2013, were $42.6 million. The price per unit in the table above represents an average price for all issuances under the Continuous Offering Program during 2013.

[6]

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 $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Earnings Per Unit [Line Items]
Net income attributable to Western Gas Partners, LP	$376,533		$274,627		$134,377
Pre-acquisition net (income) loss allocated to Anadarko	956		-4,128		-27,391
General partner interest in net (income) loss	-120,980	[1]	-69,633	[1]	-28,089	[1]
Limited partners' interest in net income	256,509	[1]	200,866	[1]	78,897	[1]
Net income per common unit - basic	$2.13	[2]	$1.83	[2]	$0.84	[2]
Net income per common unit - diluted	$2.12	[2]	$1.83	[2]	$0.84	[2]
Weighted average limited partnership units outstanding diluted	120,928		109,872		93,936
Common Units [Member]
Earnings Per Unit [Line Items]
Limited partners' interest in net income	254,737		200,866		78,897
Weighted average limited partnership units outstanding basic	119,822		109,872		93,936
Class C Units [Member]
Earnings Per Unit [Line Items]
Limited partners' interest in net income	$1,772		$0		$0
Weighted average limited partnership units outstanding basic	1,106		0		0
[1]	Represents net income earned on and subsequent to the date of acquisition of the Partnership assets (as defined in Note 1). See Note 4.
[2]	See Note 4 for the calculation of net income per unit.

Equity_and_Partners_Capital_Ad

Equity and Partners' Capital - Additional Information (details) (USD $)	1 Months Ended		12 Months Ended	0 Months Ended	12 Months Ended
	Nov. 30, 2014		Dec. 31, 2014	Nov. 25, 2014	Dec. 31, 2013		Dec. 31, 2012	31-May-13		Jun. 30, 2012
Schedule Of Investments [Line Items]
Price per unit	$70.85	[1]			$61.51	[2]		$61.18	[3]	$43.88
Beneficial conversion feature of Class C units			$0
General partner units owned			2,583,068		2,394,345
General partner's interest	2.00%
Western Gas Equity Partners [Member]
Schedule Of Investments [Line Items]
Limited partner units owned			49,296,205
Ownership interest			34.90%
General partner's interest			1.80%
Other Subsidiaries Of Anadarko [Member]
Schedule Of Investments [Line Items]
Ownership interest			8.30%
Public [Member]
Schedule Of Investments [Line Items]
Ownership interest			55.00%
Class C Units [Member]
Schedule Of Investments [Line Items]
Class C units issued			10,913,853
Price per unit				$68.72
Proceeds from the issuance of Class C units			750,000,000	750,000,000	0		0
Beneficial conversion feature of Class C units			34,800,000
Limited partner units owned			10,913,853		0
Class C Units [Member] | Other Subsidiaries Of Anadarko [Member]
Schedule Of Investments [Line Items]
Class C units issued	10,913,853		10,913,853
Limited partner units owned			10,913,853
Incentive Distribution Rights [Member] | Western Gas Equity Partners [Member]
Schedule Of Investments [Line Items]
General partner's interest			100.00%
Common Units [Member]
Schedule Of Investments [Line Items]
Limited partner units owned			127,695,130		117,322,812
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			77,641,306
Maximum [Member] | Class C Units [Member]
Schedule Of Investments [Line Items]
Redeemable option on units	$150,000,000
[1]	Includes the issuance of 1,120,153 common units pursuant to the partial exercise of the underwriters’ over-allotment option. Net proceeds from this partial exercise were $77.0 million. Beginning with this partial exercise, the Partnership’s general partner elected not to make a corresponding capital contribution to maintain the general partner’s 2.0% interest in the Partnership. See Note 3.
[2]	Includes the issuance of 300,000 common units on January 3, 2014, pursuant to the partial exercise of the underwriters’ over-allotment option. Net proceeds from this partial exercise (including the general partner’s proportionate capital contribution) were $18.1 million.
[3]	Includes the issuance of 915,000 common units pursuant to the full exercise of the underwriters’ over-allotment option.

Transactions_With_Affiliates_C

Transactions With Affiliates - Commodity Price Swap Agreements Table (details)	Dec. 31, 2014
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 $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	$54,868		$38,164		$14,215
Sales [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	123,360	[1]	123,458	[1]	103,925	[1]
Sales [Member] | Natural Gas [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	9,494	[1]	21,382	[1]	37,665	[1]
Sales [Member] | Natural Gas Liquids [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	113,866	[1]	102,076	[1]	66,260	[1]
Cost of Sales [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	($68,492)	[2]	($85,294)	[2]	($89,710)	[2]
[1]	Reported in affiliate natural gas, natural gas liquids and 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_O

Transactions With Affiliates - Omnibus Agreement Table (details) (Omnibus Agreement [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Allocated costs from Anadarko	$28,255	$24,034	$21,734
General and Administrative Expenses [Member]
Related Party Transaction [Line Items]
Allocated costs from Anadarko	20,249	16,882	14,904
Public Company Expenses [Member]
Related Party Transaction [Line Items]
Allocated costs from Anadarko	$8,006	$7,152	$6,830

Transactions_With_Affiliates_L

Transactions With Affiliates - LTIP Award Activity Table (details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Phantom units outstanding at beginning of year	16,844	25,619	23,978
Vested	-13,122	-14,695	-14,260
Granted	5,800	5,920	15,901
Phantom units outstanding at end of year	9,522	16,844	25,619
Value per unit of phantom units outstanding	$60.74	$49.47	$41.77	$33.92
Value per unit of phantom units vested during the period	$49.55	$41.28	$33.20
Value per unit of phantom units granted during the period	$68.14	$62.49	$45.91

Transactions_With_Affiliates_E

Transactions With Affiliates - Equipment Purchases and Sales Table (details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Partners' capital adjustment	$10,733	$5,855	$15,296
Affiliated Entity [Member] | Purchases [Member]
Related Party Transaction [Line Items]
Consideration given for equipment	22,943	11,211	24,705
Net carrying value	12,210	5,309	8,009
Partners' capital adjustment	10,733	5,902	16,696
Affiliated Entity [Member] | Sales [Member]
Related Party Transaction [Line Items]
Consideration received for equipment	0	85	760
Net carrying value	0	38	393
Partners' capital adjustment	$0	$47	$367

Transactions_With_Affiliates_S

Transactions With Affiliates - Summary Table (details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Related Party Transaction [Line Items]
Revenues	$1,273,763		$1,029,763		$894,476
Equity income, net	57,836	[1],[2],[3]	22,948	[1],[2],[3]	16,042	[1],[2],[3]
Cost of product	437,956	[4]	364,285	[4]	336,079	[4]
Operation and maintenance	199,305	[4]	168,657	[4]	140,106	[4]
General and administrative	34,242	[4]	29,751	[4]	99,212	[4]
Operating expenses	880,012		731,853		715,693
Interest income	16,900	[5]	16,900	[5]	16,900	[5]
Interest expense	76,766	[6]	51,797	[6]	42,060	[6]
Distributions to unitholders	408,621		299,101		197,850
Contributions from noncontrolling interest owners	0		2,247		29,108
Distributions to noncontrolling interest owners	15,149		13,127		17,303
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Revenues	969,995	[1]	805,526	[1]	688,026	[1]
Cost of product	114,000	[1]	129,045	[1]	145,250	[1]
Operation and maintenance	58,884	[7]	56,435	[7]	51,237	[7]
General and administrative	26,989	[8]	23,354	[8]	92,847	[8]
Operating expenses	199,873		208,834		289,334
Interest expense	0	[9]	0	[9]	2,766	[9]
Distributions to unitholders	234,024	[10]	169,150	[10]	98,280	[10]
Contributions from noncontrolling interest owners	0	[11]	0	[11]	12,588	[11]
Distributions to noncontrolling interest owners	$0	[11]	$0	[11]	$6,528	[11]
[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]	Income earned on, distributions from and contributions to equity investments are classified as affiliate. See Note 1.
[3]	Income earned from equity investments is classified as affiliate. See Note 1.
[4]	Cost of product includes product purchases from Anadarko (as defined in Note 1) of $114.0 million, $129.0 million and $145.3 million for the years ended December 31, 2014, 2013 and 2012, respectively. Operation and maintenance includes charges from Anadarko of $58.9 million, $56.4 million and $51.2 million for the years ended December 31, 2014, 2013 and 2012, respectively. General and administrative includes charges from Anadarko of $27.0 million, $23.4 million and $92.8 million for the years ended December 31, 2014, 2013 and 2012, respectively. See Note 5.
[5]	Represents interest income recognized on the note receivable from Anadarko.
[6]	Includes affiliate (as defined in Note 1) interest expense of zero for each of the years ended December 31, 2014 and 2013, and $2.8 million for the year ended December 31, 2012. See Note 12.
[7]	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.
[8]	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, WGP LTIP and Anadarko Incentive Plans, and The Incentive Plan within this Note 5).
[9]	For the year ended December 31, 2012, includes interest expense recognized on the note payable to Anadarko (see Note 12) and interest imputed on the reimbursement payable to Anadarko for certain expenditures Anadarko incurred in 2011 related to the construction of the Brasada complex and Lancaster plant. The Partnership repaid the note payable to Anadarko in June 2012, and repaid the reimbursement payable to Anadarko associated with the construction of the Brasada complex and Lancaster plant in the fourth quarter of 2012.
[10]	Represents distributions paid under the partnership agreement (see Note 3 and Note 4).
[11]	As described in Note 2, the Partnership acquired the additional Chipeta interest on August 1, 2012, and accounted for the acquisition on a prospective basis. As such, contributions from noncontrolling interest owners and distributions to noncontrolling interest owners subsequent to the acquisition date no longer reflect contributions from or distributions to Anadarko.

Transactions_With_Affiliates_A

Transactions With Affiliates - Additional Information (details) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	31-May-08	Dec. 31, 2008	Jun. 30, 2012
Related Party Transaction [Line Items]
Note receivable - Anadarko	$260,000,000	$260,000,000
Partners' capital adjustment	482,000	345,000	3,065,000
Western Gas Partners Long Term Incentive Plan [Member]
Related Party Transaction [Line Items]
Phantom units vesting period	3 years
Equity-based compensation expense	600,000	600,000	400,000
Unvested equity-based compensation expense	200,000
Weighted-average term of unvested awards	8 months 12 days
Western Gas Equity Partners Long Term Incentive Plan [Member] | Anadarko Incentive Plans [Member]
Related Party Transaction [Line Items]
Equity-based compensation expense	3,500,000	3,000,000	3,300,000
Unvested equity-based compensation expense	7,200,000
Weighted-average term of unvested awards	2 years 1 month 6 days
Partners' capital adjustment	3,200,000	2,900,000	3,200,000
Incentive Plan [Member]
Related Party Transaction [Line Items]
Equity-based compensation expense			68,800,000
Incentive Plan [Member] | Unit Appreciation Right [Member]
Related Party Transaction [Line Items]
UAR and DER valuation			$2,745
Incentive Plan [Member] | Distribution Equivalent Right [Member]
Related Party Transaction [Line Items]
UAR and DER valuation			$12
Independent Director [Member] | Western Gas Partners Long Term Incentive Plan [Member]
Related Party Transaction [Line Items]
Phantom units vesting period	1 year
Anadarko [Member] | Western Gas Partners Long Term Incentive Plan [Member]
Related Party Transaction [Line Items]
Unvested equity-based compensation expense	300,000
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	317,800,000	296,700,000
Note Payable To Anadarko [Member]
Related Party Transaction [Line Items]
Principal					$175,000,000
Debt instrument, maturity date	2-Aug-13
Senior Notes 4 Percent Due 2022 [Member]
Related Party Transaction [Line Items]
Fixed interest rate						4.00%
Gathering Transportation And Treating [Member]
Related Party Transaction [Line Items]
Affiliate throughput percent	48.00%	54.00%	62.00%
Processing [Member]
Related Party Transaction [Line Items]
Affiliate throughput percent	57.00%	59.00%	61.00%

Income_Taxes_Components_of_Inc

Income Taxes - Components of Income Tax Expense (Benefit) Table (details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current Income Tax Expense (Benefit) [Abstract]
Federal income tax expense (benefit)	($625)	($30,176)	($7,576)
State income tax expense (benefit)	69	640	-1,843
Total current income tax expense (benefit)	-556	-29,536	-9,419
Deferred Income Tax Expense (Benefit) [Abstract]
Federal income tax expense (benefit)	171	32,930	22,324
State income tax expense (benefit)	2,412	-1,039	7,785
Total deferred income tax expense (benefit)	2,583	31,891	30,109
Total income tax expense	$2,027	$2,355	$20,690

Income_Taxes_Tax_Rate_Reconcil

Income Taxes - Tax Rate Reconciliation Table (details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Income before income taxes	$392,585	$287,798	$169,957
Statutory tax rate	0.00%	0.00%	0.00%
Adjustments Resulting From [Abstract]
State taxes on income attributable to Partnership assets pre-acquisition (net of federal benefit) Texas margin tax expense (benefit)	2,481	-1,359	1,258
Income tax expense	2,027	2,355	20,690
Effective tax rate	1.00%	1.00%	12.00%
Pre Acquisition From Parent [Member]
Adjustments Resulting From [Abstract]
Federal taxes on income attributable to Partnership assets pre-acquisition	-454	3,090	17,226
State taxes on income attributable to Partnership assets pre-acquisition (net of federal benefit) Texas margin tax expense (benefit)	$0	$624	$2,206

Income_Taxes_Income_Tax_Tempor

Income Taxes - Income Tax Temporary Differences Table (details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Income Tax Disclosure [Abstract]
Credit carryforwards	$14	$14
Net current deferred income tax assets	14	14
Depreciable property	-3,240	-38,528
Credit carryforwards	512	527
Other intangible assets	-1,450	0
Other	7	3
Net long-term deferred income tax liabilities	-4,171	-37,998
Total net deferred income tax liabilities	($4,157)	($37,984)

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Credit carryforwards	$512	$527
Tax credit carryforward, expiration date	31-Dec-26

Recovered_Sheet1

Property, Plant and Equipment Table (details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property, plant and equipment	5,424,699	$4,239,100
Accumulated depreciation	1,040,328	855,845
Net property, plant and equipment	4,384,371	3,383,255
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	2,839	2,584
Gathering Systems [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	4,790,974	3,673,008
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	151,107	146,008
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	464,507	405,633
Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	15,272	$11,867
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

Property_Plant_and_Equipment_A

Property, Plant and Equipment - Additional Information (details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2014
Property, Plant and Equipment [Line Items]
Unguaranteed residual value		$4,600,000
Property, plant and equipment	5,424,699,000	4,239,100,000
Impairment	3,100,000	1,200,000
Natural Gas Processing Plant [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	4,600,000			4,600,000
Equipment [Member]
Property, Plant and Equipment [Line Items]
Impairment			600,000
Estimated fair value	2,400,000
Natural Gas Gathering Systems [Member]
Property, Plant and Equipment [Line Items]
Impairment			$6,000,000

Goodwill_and_Intangibles_Other

Goodwill and Intangibles - Other Intangible Assets Table (details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Goodwill and Intangible Assets Disclosure [Abstract]
Gross carrying amount	$892,555	$56,988
Accumulated amortization	-7,698	-3,382
Other intangible assets	$884,857	$53,606

Goodwill_and_Intangibles_Addit

Goodwill and Intangibles - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Goodwill	$384,387,000	$105,336,000
Amortization expense for intangible assets	4,300,000	1,400,000	1,100,000
Estimated amortization expense for intangible assets in 2015	29,100,000
Estimated amortization expense for intangible assets in 2016	29,200,000
Estimated amortization expense for intangible assets in 2017	29,200,000
Estimated amortization expense for intangible assets in 2018	29,200,000
Estimated amortization expense for intangible assets in 2019	29,200,000
Platte Valley [Member]
Finite-Lived Intangible Assets [Line Items]
Straight-line basis of amortization	50 years
Chipeta Processing Limited Liability Company [Member]
Finite-Lived Intangible Assets [Line Items]
Straight-line basis of amortization	10 years
Delaware Basin Midstream Limited Liability Company [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	$279,051,000
Straight-line basis of amortization	30 years

Equity_Investments_Equity_Inve

Equity Investments - Equity Investments Table (details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Balance	$593,400		$219,766
Initial investment			78,129
Investment earnings (loss), net of amortization	57,836	[1],[2],[3]	22,948	[1],[2],[3]	16,042	[1],[2],[3]
Contributions	64,278		294,693		108,457
Capitalized interest	857		17,033
Distributions	-62,967	[1]	-17,698	[1]	-20,660	[1]
Distributions in excess of cumulative earnings	-18,055	[1],[4]	-4,438	[1],[4]	0	[1]
Balance	634,492		593,400		219,766
Equity Investments [Member]
Schedule of Equity Method Investments [Line Items]
Contributions	63,421		277,660
Fort Union [Member]
Schedule of Equity Method Investments [Line Items]
Balance	25,172	[5]	23,453	[5]
Initial investment			0	[5]
Investment earnings (loss), net of amortization	6,344	[5]	6,273	[5]
Contributions	0	[5]	16	[5]
Capitalized interest	0	[5]	0	[5]
Distributions	-5,583	[5]	-4,570	[5]
Distributions in excess of cumulative earnings	0	[4],[5]	0	[4],[5]
Balance	25,933	[5]	25,172	[5]
Table Text Block Supplement [Abstract]
Equity investment ownership	14.81%
Approval percentage	65.00%
White Cliffs [Member]
Schedule of Equity Method Investments [Line Items]
Balance	35,039	[6]	17,567	[6]
Initial investment			0	[6]
Investment earnings (loss), net of amortization	11,912	[6]	9,681	[6]
Contributions	10,456	[6]	19,087	[6]
Capitalized interest	0	[6]	0	[6]
Distributions	-11,330	[6]	-9,099	[6]
Distributions in excess of cumulative earnings	-1,762	[4],[6]	-2,197	[4],[6]
Balance	44,315	[6]	35,039	[6]
Table Text Block Supplement [Abstract]
Equity investment ownership	10.00%
Approval percentage	75.00%
Rendezvous [Member]
Schedule of Equity Method Investments [Line Items]
Balance	60,928	[7]	65,110	[7]
Initial investment			0	[7]
Investment earnings (loss), net of amortization	1,729	[7]	2,088	[7]
Contributions	0	[7]	0	[7]
Capitalized interest	0	[7]	0	[7]
Distributions	-3,669	[7]	-4,029	[7]
Distributions in excess of cumulative earnings	-2,652	[4],[7]	-2,241	[4],[7]
Balance	56,336	[7]	60,928	[7]
Table Text Block Supplement [Abstract]
Equity investment ownership	22.00%
Approval percentage	100.00%
Mont Belvieu Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Balance	122,480	[8]	0	[8]
Initial investment			78,129	[8]
Investment earnings (loss), net of amortization	29,029	[8]	5,690	[8]
Contributions	3,957	[8]	37,309	[8]
Capitalized interest	0	[8]	1,352	[8]
Distributions	-34,129	[8]	0	[8]
Distributions in excess of cumulative earnings	0	[4],[8]	0	[4],[8]
Balance	121,337	[8]	122,480	[8]
Table Text Block Supplement [Abstract]
Equity investment ownership	25.00%
Approval percentage	50.00%
Mont Belvieu Joint Venture [Member] | Fractionation Train [Member]
Table Text Block Supplement [Abstract]
Assets, number of units	2
Texas Express Gathering Limited Liability Company [Member]
Schedule of Equity Method Investments [Line Items]
Balance	16,649	[9]	9,033	[9]
Initial investment			0	[9]
Investment earnings (loss), net of amortization	650	[9]	93	[9]
Contributions	352	[9]	6,732	[9]
Capitalized interest	0	[9]	791	[9]
Distributions	-523	[9]	0	[9]
Distributions in excess of cumulative earnings	-338	[4],[9]	0	[4],[9]
Balance	16,790	[9]	16,649	[9]
Table Text Block Supplement [Abstract]
Equity investment ownership	20.00%
Approval percentage	50.00%
Texas Express Gathering Limited Liability Company [Member] | Natural Gas Liquids Gathering System [Member]
Table Text Block Supplement [Abstract]
Assets, number of units	2
Texas Express Pipeline Limited Liability Company [Member]
Schedule of Equity Method Investments [Line Items]
Balance	197,731	[10]	80,737	[10]
Initial investment			0	[10]
Investment earnings (loss), net of amortization	6,108	[10]	-776	[10]
Contributions	6,623	[10]	108,969	[10]
Capitalized interest	0	[10]	8,801	[10]
Distributions	-5,622	[10]	0	[10]
Distributions in excess of cumulative earnings	-6,047	[10],[4]	0	[10],[4]
Balance	198,793	[10]	197,731	[10]
Table Text Block Supplement [Abstract]
Equity investment ownership	20.00%
Approval percentage	50.00%
Front Range Pipeline Limited Liability Company [Member]
Schedule of Equity Method Investments [Line Items]
Balance	135,401	[11]	23,866	[11]
Initial investment			0	[11]
Investment earnings (loss), net of amortization	2,064	[11]	-101	[11]
Contributions	42,033	[11]	105,547	[11]
Capitalized interest	857	[11]	6,089	[11]
Distributions	-2,111	[11]	0	[11]
Distributions in excess of cumulative earnings	-7,256	[11],[4]	0	[11],[4]
Balance	$170,988	[11]	$135,401	[11]
Table Text Block Supplement [Abstract]
Equity investment ownership	33.33%
Approval percentage	50.00%
[1]	Income earned on, distributions from and contributions to equity investments are classified as affiliate. See Note 1.
[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]	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.
[5]	The Partnership has a 14.81% interest in Fort Union, a joint venture that owns a gathering pipeline and treating facilities in the Powder River Basin. Anadarko is the construction manager and physical operator of the Fort Union facilities. Certain business decisions, including, but not limited to, decisions with respect to significant expenditures or contractual commitments, annual budgets, material financings, dispositions of assets or amending the owners’ firm gathering agreements, require 65% or unanimous approval of the owners.
[6]	The Partnership has a 10% interest in White Cliffs, a limited liability company that owns a crude oil pipeline that originates in Platteville, Colorado and terminates in Cushing, Oklahoma. The third-party majority owner is the manager of the White Cliffs operations. Certain business decisions, including, but not limited to, approval of annual budgets and decisions with respect to significant expenditures, contractual commitments, acquisitions, material financings, dispositions of assets or admitting new members, require more than 75% approval of the members.
[7]	The Partnership has a 22% interest in Rendezvous, a limited liability company that operates gas gathering facilities in Southwestern Wyoming. Certain business decisions, including, but not limited to, decisions with respect to significant expenditures or contractual commitments, annual budgets, material financings, dispositions of assets or amending the members’ gas servicing agreements, require unanimous approval of the members.
[8]	The Partnership has a 25% interest in the Mont Belvieu JV, an entity formed to design, construct, and own two fractionation trains located in Mont Belvieu, Texas. A third party is the operator of the Mont Belvieu JV fractionation trains. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the creation, appointment, or removal of officer positions require 50% or unanimous approval of the owners.
[9]	The Partnership has a 20% interest in TEG, an entity that consists of two NGL gathering systems that link natural gas processing plants to TEP. Enbridge Midcoast Energy, LP (“Enbridge”) is the operator of the two gathering systems. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the delegation, creation, appointment, or removal of officer positions require more than 50% approval of the members.
[10]	The Partnership has a 20% interest in TEP, which consists of an NGL pipeline that originates in Skellytown, Texas and extends to Mont Belvieu, Texas. Enterprise Products Operating LLC (“Enterprise”) is the operator of TEP. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the creation, appointment, or removal of officer positions require more than 50% approval of the members.
[11]	The Partnership has a 33.33% interest in the FRP, an NGL pipeline that extends from Weld County, Colorado to Skellytown, Texas. Enterprise is the operator of FRP. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the creation, appointment, or removal of officer positions require more than 50% approval of the members.

Equity_Investments_Summarized_

Equity Investments - Summarized Combined Financial Data For Equity Investments - Income Statement Table (details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity Method Investments and Joint Ventures [Abstract]
Revenues	$548,629	$261,705	$199,764
Operating income	336,188	171,496	135,498
Net income	$333,705	$170,175	$133,987

Equity_Investments_Summarized_1

Equity Investments - Summarized Combined Financial Data For Equity Investments - Balance Sheet Table (details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Equity Method Investments and Joint Ventures [Abstract]
Current assets	$141,781	$186,690
Property, plant and equipment, net	2,814,336	2,676,531
Other assets	48,799	38,258
Total assets	3,004,916	2,901,479
Current liabilities	95,102	206,602
Non-current liabilities	22,615	34,012
Equity	2,887,199	2,660,865
Total liabilities and equity	$3,004,916	$2,901,479

Equity_Investments_Additional_

Equity Investments - Additional Information (details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Fort Union [Member]
Schedule of Equity Method Investments [Line Items]
Equity investment difference between carrying and underlying value	$2.30
Equity investment ownership	14.81%
Rendezvous [Member]
Schedule of Equity Method Investments [Line Items]
Equity investment difference between carrying and underlying value	42.1
Equity investment ownership	22.00%
White Cliffs [Member]
Schedule of Equity Method Investments [Line Items]
Equity investment difference between carrying and underlying value	($9)
Equity investment ownership	10.00%
White Cliffs [Member] | Affiliated Entity [Member]
Schedule of Equity Method Investments [Line Items]
Equity investment ownership	0.40%

Components_of_Working_Capital_1

Components of Working Capital - Other Current Assets Table (details) (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified
Other Current Assets [Line Items]
Natural gas liquids inventory	$5,316		$2,584
Natural gas imbalance receivables	415		3,605
Prepaid insurance	2,443		2,123
Other	1,893		1,710
Total other current assets	$10,067	[1]	$10,022	[1]
[1]	Other current assets includes natural gas imbalance receivables from affiliates of $0.2 million and $0.1 million as of December 31, 2014 and 2013, respectively.

Components_of_Working_Capital_2

Components of Working Capital - Accrued Liabilities Table (details) (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified
Accrued Liabilities [Line Items]
Other accrued liabilities	$1,106		$218
Accrued interest expense	24,741		18,119
Short-term asset retirement obligations	1,212		1,966
Short-term remediation and reclamation obligations	475		562
Income taxes payable	207		0
Total accrued liabilities	158,655	[1]	137,011	[1]
Accrued Capital Expenditures [Member]
Accrued Liabilities [Line Items]
Other accrued liabilities	116,891		94,750
Accrued Plant Purchases [Member]
Accrued Liabilities [Line Items]
Other accrued liabilities	$14,023		$21,396
[1]	Accrued liabilities includes amounts payable to affiliates of zero and $0.1 million as of December 31, 2014 and 2013, respectively.

Recovered_Sheet2

Asset Retirement Obligations Table (details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Carrying amount of asset retirement obligations at beginning of year	$78,035	$66,723
Liabilities incurred	13,769	14,143
Liabilities settled	-4,181	-1,943
Accretion expense	4,846	4,326
Revisions in estimated liabilities	16,623	-5,214
Carrying amount of asset retirement obligations at end of year	$109,092	$78,035

Debt_and_Interest_Expense_Debt

Debt and Interest Expense - Debt Outstanding Table (details) (USD $)	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2008
Debt Instrument [Line Items]
Carrying Value	$2,422,954,000		$1,418,169,000		$1,168,278,000
Fair Value	2,511,253,000	[1]	1,422,840,000	[1]
Total long-term debt principal	2,430,000,000		1,420,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal	510,000,000		0
Carrying Value	510,000,000		0
Fair Value	510,000,000	[1]	0	[1]
Senior Notes 5 Point 375 Percent Due 2021 [Member]
Debt Instrument [Line Items]
Principal	500,000,000		500,000,000
Carrying Value	495,714,000		495,173,000
Fair Value	549,530,000	[1]	533,615,000	[1]
Senior Notes 4 Percent Due 2022 [Member]
Debt Instrument [Line Items]
Principal	670,000,000		670,000,000
Carrying Value	672,930,000		673,278,000
Fair Value	681,942,000	[1]	641,237,000	[1]
Senior Notes 2 Point 6 Percent Due 2018 [Member]
Debt Instrument [Line Items]
Principal	350,000,000		250,000,000
Carrying Value	350,474,000		249,718,000
Fair Value	352,162,000	[1]	247,988,000	[1]
Senior Notes 5 Point 45 Percent Due 2044 [Member]
Debt Instrument [Line Items]
Principal	400,000,000		0
Carrying Value	393,836,000		0
Fair Value	417,619,000	[1]	0	[1]
Note Payable To Anadarko [Member]
Debt Instrument [Line Items]
Principal						$175,000,000
[1]	Fair value is measured using Level 2 inputs.

Debt_and_Interest_Expense_Debt1

Debt and Interest Expense - Debt Activity Table (details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Beginning Balance	$1,418,169	$1,168,278
Other	-5,215	109
Ending Balance	2,422,954	1,418,169
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Beginning Balance	0
Borrowings	1,160,000	710,000
Repayments	-650,000	-710,000
Ending Balance	510,000	0
Senior Notes 5 Point 45 Percent Due 2044 [Member]
Debt Instrument [Line Items]
Beginning Balance	0
Borrowings	400,000
Ending Balance	393,836
Senior Notes 2 Point 6 Percent Due 2018 [Member]
Debt Instrument [Line Items]
Beginning Balance	249,718
Borrowings	100,000	250,000
Ending Balance	$350,474	$249,718

Debt_and_Interest_Expense_Inte

Debt and Interest Expense - Interest Expense Table (details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
Interest expense	$76,766	[1]	$51,797	[1]	$42,060	[1]
Third Parties [Member]
Debt Instrument [Line Items]
Interest expense on long-term debt	81,495		59,293		41,171
Amortization of debt issuance costs and commitment fees	5,103		4,449		4,319
Capitalized interest	-9,832		-11,945		-6,196
Affiliated Entity [Member]
Debt Instrument [Line Items]
Interest expense on note payable to Anadarko	0	[2]	0	[2]	2,440	[2]
Interest expense on affiliate balances	0	[3]	0	[3]	326	[3]
Interest expense	$0	[4]	$0	[4]	$2,766	[4]
[1]	Includes affiliate (as defined in Note 1) interest expense of zero for each of the years ended December 31, 2014 and 2013, and $2.8 million for the year ended December 31, 2012. See Note 12.
[2]	In June 2012, the note payable to Anadarko was repaid in full. See Note payable to Anadarko within this Note 12.
[3]	Imputed interest expense on the reimbursement payable to Anadarko for certain expenditures Anadarko incurred in 2011 related to the construction of the Brasada complex and Lancaster plant. In the fourth quarter of 2012, the Partnership repaid the reimbursement payable to Anadarko associated with the construction of the Brasada complex and Lancaster plant.
[4]	For the year ended December 31, 2012, includes interest expense recognized on the note payable to Anadarko (see Note 12) and interest imputed on the reimbursement payable to Anadarko for certain expenditures Anadarko incurred in 2011 related to the construction of the Brasada complex and Lancaster plant. The Partnership repaid the note payable to Anadarko in June 2012, and repaid the reimbursement payable to Anadarko associated with the construction of the Brasada complex and Lancaster plant in the fourth quarter of 2012.

Debt_and_Interest_Expense_Addi

Debt and Interest Expense - Additional Information (details) (USD $)	12 Months Ended			1 Months Ended	0 Months Ended		1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 28, 2014	Mar. 03, 2014		Mar. 31, 2014	Jun. 30, 2012	Mar. 31, 2011	Dec. 31, 2010	Dec. 31, 2008
Debt Instrument [Line Items]
Borrowings	$1,646,878,000	$957,503,000	$1,041,648,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit, expiration date	26-Feb-19
Principal	510,000,000	0
Revolving credit facility, maximum borrowing capacity				1,200,000,000					800,000,000
Revolving credit facility, expandable maximum borrowing capacity				1,500,000,000
Revolving credit facility, interest rate at period end	1.47%	1.67%
Facility fee	0.20%	0.25%
Outstanding borrowings	510,000,000
Outstanding letters of credit	12,800,000
Available borrowing capacity	677,200,000
Revolving Credit Facility [Member] | Alternate Base Rate [Member]
Debt Instrument [Line Items]
Interest rate percent above LIBOR				1.00%
Minimum [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest rate percent above LIBOR				0.98%
Facility fee				0.15%
Minimum [Member] | Revolving Credit Facility [Member] | Alternate Base Rate [Member]
Debt Instrument [Line Items]
Interest rate percent above LIBOR				0.00%
Maximum [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest rate percent above LIBOR				1.45%
Facility fee				0.30%
Maximum [Member] | Revolving Credit Facility [Member] | Alternate Base Rate [Member]
Debt Instrument [Line Items]
Interest rate percent above LIBOR				0.45%
Texas Express And Front Range [Member]
Debt Instrument [Line Items]
Borrowings					350,000,000	[1]
Texas Express And Front Range [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowings							350,000,000
Senior Notes 5 Point 375 Percent Due 2021 [Member]
Debt Instrument [Line Items]
Fixed interest rate	5.38%
Debt instrument, maturity date	1-Jun-21
Principal	500,000,000	500,000,000
Senior Notes 2 Point 6 Percent Due 2018 [Member]
Debt Instrument [Line Items]
Fixed interest rate	2.60%
Offering percent							100.86%
Effective interest rate	2.74%
Underwriting discount							600,000
Debt instrument, maturity date	15-Aug-18
Principal	350,000,000	250,000,000
Senior Notes 4 Percent Due 2022 [Member]
Debt Instrument [Line Items]
Fixed interest rate	4.00%
Debt instrument, maturity date	1-Jul-22
Principal	670,000,000	670,000,000
Senior Notes 4 Percent Due 2022 [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Realized loss on terminated swap agreement								1,700,000
Senior Notes 5 Point 45 Percent Due 2044 [Member]
Debt Instrument [Line Items]
Fixed interest rate	5.45%
Offering percent							98.44%
Effective interest rate	5.63%
Underwriting discount							3,500,000
Debt instrument, maturity date	1-Apr-44
Principal	400,000,000	0
Note Payable To Anadarko [Member]
Debt Instrument [Line Items]
Fixed interest rate										2.82%
Debt instrument, maturity date	2-Aug-13
Principal											$175,000,000
Percentage Above Federal Funds Effective Rate [Member] | Revolving Credit Facility [Member] | Alternate Base Rate [Member]
Debt Instrument [Line Items]
Interest rate percent above LIBOR				0.50%
[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.

Commitments_and_Contingencies_1

Commitments and Contingencies - Operating Lease Obligations Table (details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Commitments and Contingencies [Abstract]
2015	$338
2016	303
2017	157
2018	34
2019	0
Thereafter	0
Total	$832

Commitments_and_Contingencies_2

Commitments and Contingencies - Additional Information (details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Long-term liability for remediation and reclamation obligations	$1.50	$1.90
Term of obligation	5 years
Committed capital	64.1
Rent expense associated with office, warehouse and equipment leases	$3.50	$2.80	$3