Transactions With Affiliates - Summary Table (details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Related Party Transaction [Line Items]
Revenues	$ 1,273,763,000		$ 1,029,763,000		$ 894,476,000
Equity income, net	57,836,000	[1],[2],[3]	22,948,000	[1],[2],[3]	16,042,000	[1],[2],[3]
Cost of product	437,956,000	[4]	364,285,000	[4]	336,079,000	[4]
Operation and maintenance	199,305,000	[4]	168,657,000	[4]	140,106,000	[4]
General and administrative	37,458,000	[4]	33,464,000	[4]	99,728,000	[4]
Operating expenses	883,262,000		735,566,000		716,209,000
Interest income	16,900,000	[5]	16,900,000	[5]	16,900,000	[5]
Interest expense	76,769,000	[6]	51,797,000	[6]	42,060,000	[6]
Distributions to unitholders	228,481,000		137,000,000		0
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Revenues	969,995,000	[1]	805,526,000	[1]	688,026,000	[1]
Cost of product	114,000,000	[1]	129,045,000	[1]	145,250,000	[1]
Operation and maintenance	58,884,000	[7]	56,435,000	[7]	51,237,000	[7]
General and administrative	27,736,000	[8]	24,235,000	[8]	92,887,000	[8]
Operating expenses	200,620,000		209,715,000		289,374,000
Interest expense	3,000	[9]	0	[9]	2,766,000	[9]
Contributions from Anadarko as a Chipeta noncontrolling interest owner	0	[10]	0	[10]	12,588,000	[10]
Distributions to Anadarko as a Chipeta noncontrolling interest owner	0	[10]	0	[10]	6,528,000	[10]
Affiliated Entity [Member] | Western Gas Equity Partners [Member]
Related Party Transaction [Line Items]
Distributions to unitholders	204,615,000	[11]	124,633,000	[11]	0	[11]
Western Gas Partners [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Distributions to unitholders	$ 1,747,000	[12]	$ 755,000	[12]	$ 0	[12]

[1] Represents amounts earned or incurred on and subsequent to the date of acquisition of WES assets, as well as amounts earned or incurred by Anadarko on a historical basis related to WES assets prior to the acquisition of such assets by WES, recognized under gathering, treating or processing agreements, and purchase and sale agreements.

[2] Income earned from equity investments is classified as affiliate. See Note 1.

[3] Income earned on, distributions from and contributions to equity investments are 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 $27.7 million, $24.2 million and $92.9 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 13.

[7] 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.

[8] 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 and WGP by Anadarko (see Note 6) and amounts charged by Anadarko under the WGP omnibus agreement.

[9] For the year ended December 31, 2014, includes interest expense recognized on the WGP working capital facility (see Note 13). For the year ended December 31, 2012, includes interest expense recognized on the WES note payable to Anadarko (see Note 13) 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. WES repaid the WES 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] As described in Note 2, WES 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.

[11] Represents distributions paid under WGP’s partnership agreement (see Note 3 and Note 4).

[12] Represents distributions paid to other subsidiaries of Anadarko under WES’s partnership agreement (see Note 3 and Note 4).