Transactions With Affiliates - Summary Table (details) (USD $) In Thousands, unless otherwise specified	3 Months Ended							9 Months Ended				3 Months Ended							9 Months Ended			3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended
	Sep. 30, 2013		Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013 Western Gas Partners [Member]		Jun. 30, 2013 Western Gas Partners [Member]	Mar. 31, 2013 Western Gas Partners [Member]	Sep. 30, 2012 Western Gas Partners [Member]	Jun. 30, 2012 Western Gas Partners [Member]	Mar. 31, 2012 Western Gas Partners [Member]	Sep. 30, 2013 Western Gas Partners [Member]	Sep. 30, 2013 Chipeta Processing Limited Liability Company [Member] Western Gas Partners [Member]	Aug. 31, 2012 Chipeta Processing Limited Liability Company [Member] Western Gas Partners [Member]	Sep. 30, 2013 Affiliated Entity [Member]		Sep. 30, 2012 Affiliated Entity [Member]		Sep. 30, 2013 Affiliated Entity [Member]		Sep. 30, 2012 Affiliated Entity [Member]		Sep. 30, 2013 Affiliated Entity [Member] Western Gas Equity Partners [Member]		Sep. 30, 2012 Affiliated Entity [Member] Western Gas Equity Partners [Member]		Sep. 30, 2013 Affiliated Entity [Member] Western Gas Equity Partners [Member]		Sep. 30, 2012 Affiliated Entity [Member] Western Gas Equity Partners [Member]		Sep. 30, 2013 Affiliated Entity [Member] Western Gas Partners [Member]		Sep. 30, 2012 Affiliated Entity [Member] Western Gas Partners [Member]		Sep. 30, 2013 Affiliated Entity [Member] Western Gas Partners [Member]		Sep. 30, 2012 Affiliated Entity [Member] Western Gas Partners [Member]
Related Party Transaction [Line Items]
Revenues	$ 278,001					$ 234,734	[1]	$ 762,874		$ 679,720	[1]											$ 217,624	[2]	$ 180,605	[1],[2]	$ 603,214	[2]	$ 519,460	[1],[2]
Cost of product	93,516	[3]				89,107	[1],[3]	270,059	[3]	254,719	[1],[3]											33,753	[2]	42,839	[2]	97,801	[2]	115,603	[2]
Operation and maintenance	42,757	[3]				35,493	[1],[3]	121,165	[3]	103,304	[1],[3]											13,469	[4]	12,638	[4]	41,021	[4]	38,040	[4]
General and administrative	7,962	[3]				15,039	[1],[3]	25,100	[3]	35,623	[1],[3]											6,090	[5]	14,227	[5]	17,981	[5]	30,811	[5]
Operating expenses	188,499					173,422	[1]	541,395		491,907	[1]											53,312		69,704		156,803		184,454
Interest income, net	4,225	[6]				4,225	[6]	12,675	[6]	12,675	[6]
Interest expense	13,018	[7]				10,977	[1],[7]	37,483	[7]	30,118	[1],[7]											0	[8]	81	[8]	0	[8]	2,684	[8]
Distributions to unitholders	46,789	[9]	43,232	39,128	7,852							83,986	[10]	79,315	70,143	56,346	52,425	46,053												39,329	[11]	0	[11]	82,068	[11]	0	[11]	252	[12]	0	[12]	494	[12]	0	[12]
Contributions from Anadarko as a Chipeta noncontrolling interest owner								2,247														0	[13]	2,148	[13]	0	[13]	12,588	[13]
Distributions to Anadarko as a Chipeta noncontrolling interest owner																			$ 94,117			$ 0	[13]	$ 1,464	[13]	$ 0	[13]	$ 6,528	[13]
Table Text Block Supplement [Abstract]
Ownership interest by noncontrolling owners																				25.00%	24.00%

[1] Financial information has been recast to include the financial position and results attributable to the Non-Operated Marcellus Interest. See Note 2.

[2] Represents amounts recognized under gathering, treating or processing agreements, and purchase and sale agreements.

[3] Cost of product includes product purchases from Anadarko (as defined in Note 1) of $33.8 million and $97.8 million for the three and nine months ended September 30, 2013, respectively, and $42.8 million and $115.6 million for the three and nine months ended September 30, 2012, respectively. Operation and maintenance includes charges from Anadarko of $13.5 million and $41.0 million for the three and nine months ended September 30, 2013, respectively, and $12.6 million and $38.0 million for the three and nine months ended September 30, 2012, respectively. General and administrative includes charges from Anadarko of $6.1 million and $18.0 million for the three and nine months ended September 30, 2013, respectively, and $14.2 million and $30.8 million for the three and nine months ended September 30, 2012, respectively. See Note 5.

[4] Represents expenses incurred on and subsequent to the date of the acquisition of WES assets, as well as expenses incurred by Anadarko on a historical basis related to WES assets prior to the acquisition of such assets by WES.

[5] Represents general and administrative expense incurred on and subsequent to the date of WES’s acquisition of WES assets, as well as a management services fee for reimbursement of expenses incurred by Anadarko for periods prior to the acquisition of WES assets by WES. These amounts include equity-based compensation expense allocated to WES by Anadarko (see Equity incentive plan and Anadarko incentive plans within this Note 5) and amounts charged by Anadarko under the WGP omnibus agreement.

[6] Represents interest income recognized on the note receivable from Anadarko.

[7] Includes affiliate (as defined in Note 1) interest expense of zero for the three and nine months ended September 30, 2013, and $0.1 million and $2.7 million for the three and nine months ended September 30, 2012, respectively. See Note 8.

[8] For the three and nine months ended September 30, 2012, includes interest expense recognized on the WES note payable to Anadarko (see Note 8) and interest imputed on the reimbursement payable to Anadarko for certain expenditures Anadarko incurred in 2011 related to the construction of the Brasada and Lancaster plants. WES repaid the WES note payable to Anadarko in June 2012, and repaid the reimbursement payable to Anadarko related to the construction of the Brasada and Lancaster plants in the fourth quarter of 2012. See Note receivable from and amounts payable to Anadarko within this Note 5.

[9] On October 16, 2013, the board of directors of WGP GP declared a cash distribution to WGP unitholders of $0.21375 per unit, or $46.8 million in aggregate. The cash distribution is payable on November 21, 2013, to WGP unitholders of record at the close of business on October 31, 2013.

[10] On October 16, 2013, the board of directors of WES GP declared a cash distribution to WES unitholders of $0.58 per unit, or $84.0 million in aggregate, including incentive distributions. The cash distribution is payable on November 12, 2013, to WES unitholders of record at the close of business on October 31, 2013.

[11] Represents distributions paid under WGP’s partnership agreement.

[12] Represents distributions paid under WES’s partnership agreement (see Holdings of WES equity in Note 4).

[13] As described in Note 2, WES acquired Anadarko’s then remaining 24% membership interest in Chipeta 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.