Transactions with Affiliates - Summary Table (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014
Related Party Transaction [Line Items]
Revenues		$ 402,412	$ 345,569	[1]	$ 777,506		$ 639,286	[1]
Equity income, net	[2],[3]	18,941	13,008	[1]	37,161	[4]	22,259	[1],[4]
Cost of product	[5]	146,293	120,542	[1]	284,213		214,918	[1]
Operation and maintenance	[5]	56,827	55,404	[1]	112,976		99,981	[1]
General and administrative	[5]	9,442	9,202	[1]	20,789		19,077	[1]
Operating expenses		287,324	237,769	[1]	571,555		435,916	[1]
Interest income	[6]	4,225	4,225	[1]	8,450		8,450	[1]
Interest expense	[7]	27,604	20,864	[1]	50,566		34,825	[1]
Distributions to unitholders					143,386		105,347	[1]
Affiliates [Member]
Related Party Transaction [Line Items]
Revenues	[3]	259,448	266,523	[1]	505,163		481,519	[1]
Cost of product	[3]	52,139	36,890		94,546		55,246
Operation and maintenance	[8]	17,496	16,827		32,872		29,378
General and administrative	[9]	7,513	7,090		15,279		14,572
Operating expenses		77,148	60,807		142,697		99,196
Interest expense	[10]	4,190	0		5,612		0
Affiliates [Member] | Western Gas Equity Partners, LP [Member]
Related Party Transaction [Line Items]
Distributions to unitholders	[11]	66,235	49,784		126,669		95,835
Affiliates [Member] | Western Gas Partners, LP [Member]
Related Party Transaction [Line Items]
Distributions to unitholders	[12]	$ 550	$ 474		$ 1,080		$ 743

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

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

[3] Represents amounts earned or incurred on and subsequent to the date of acquisition of 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.

[4] Income earned on, distributions from and contributions to equity investments are classified as affiliate. See Note 1.

[5] Cost of product includes product purchases from Anadarko (as defined in Note 1) of $52.1 million and $94.5 million for the three and six months ended June 30, 2015, respectively, and $36.9 million and $55.2 million for the three and six months ended June 30, 2014, respectively. Operation and maintenance includes charges from Anadarko of $17.5 million and $32.9 million for the three and six months ended June 30, 2015, respectively, and $16.8 million and $29.4 million for the three and six months ended June 30, 2014, respectively. General and administrative includes charges from Anadarko of $7.5 million and $15.3 million for the three and six months ended June 30, 2015, respectively, and $7.1 million and $14.6 million for the three and six months ended June 30, 2014, respectively. See Note 5.

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

[7] Includes affiliate (as defined in Note 1) interest expense of $4.2 million and $5.6 million for the three and six months ended June 30, 2015, respectively, and zero for each of the three and six months ended June 30, 2014. See Note 2 and Note 9.

[8] 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.

[9] 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 WES LTIP and WGP LTIP and Anadarko Incentive Plans within this Note 5) and amounts charged by Anadarko under the WGP omnibus agreement.

[10] For the three and six months ended June 30, 2015, includes interest expense recognized on the WGP working capital facility (see Note 9) and WES’s accretion expense recognized on the Deferred purchase price obligation - Anadarko for the acquisition of DBJV (see Note 2 and Note 9).

[11] Represents distributions paid under 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).