Transactions with Affiliates - Summary of Affiliate Transactions Tables (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Related Party Transaction [Line Items]
Revenues and other		$ 671,883	$ 501,054	[1]
Equity income, net – affiliates	[2]	57,992	30,229	[1]
Cost of product	[3]	114,063	94,318	[1]
Operation and maintenance	[3]	142,829	96,795	[1]
General and administrative	[3]	22,844	15,829	[1]
Operating expenses		410,357	306,532	[1]
Interest income	[4]	4,225	4,225	[1]
Interest expense	[5]	65,876	38,015	[1]
Distributions to unitholders	[6]	131,910	120,140	[1]
Above-market component of swap agreements with Anadarko	[6]	7,407	14,282	[1]
WES Operating [Member]
Related Party Transaction [Line Items]
Revenues and other		671,883	501,054	[1]
Equity income, net – affiliates		57,992	30,229	[1]
Cost of product	[7]	114,063	94,318	[1]
Operation and maintenance	[7]	142,829	96,795	[1]
General and administrative	[7]	20,560	14,997	[1]
Operating expenses		408,073	305,700	[1]
Interest income	[4]	4,225	4,225	[1]
Interest expense	[8]	65,631	36,952	[1]
Distributions to unitholders	[9]	263,358	216,586	[1]
Above-market component of swap agreements with Anadarko	[9]	7,407	14,282	[1]
Affiliates [Member]
Related Party Transaction [Line Items]
Revenues and other	[2]	378,437	285,176	[1]
Cost of product	[2]	56,172	34,819
Operation and maintenance	[2]	39,141	23,001
General and administrative	[10]	18,894	12,688
Operating expenses		114,207	70,508
Interest expense	[11]	1,833	577
APCWH Note Payable borrowings	[12]	11,000	106,565
Repayment of APCWH Note Payable	[12]	439,595	0
Distributions to unitholders	[13]	102,654	98,000
Affiliates [Member] | WES Operating [Member]
Related Party Transaction [Line Items]
Revenues and other		378,437	285,176	[1]
Cost of product	[2]	56,172	34,819
Operation and maintenance	[2]	39,141	23,001
General and administrative	[14]	18,498	12,479
Interest expense	[11]	1,833	577
Distributions to unitholders	[15]	164,902	124,164
WES Operating [Member] | Affiliates [Member]
Related Party Transaction [Line Items]
Distributions to unitholders	[16]	$ 2,543	$ 1,850

[1] Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.

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

[3] Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.9 million and $12.7 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.

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

[5] Includes affiliate (as defined in Note 1) amounts of $1.8 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively. See Note 1 and Note 10.

[6] See Note 6.

[7] Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.5 million and $12.5 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.

[8] Includes affiliate (as defined in Note 1) amounts of $1.8 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively. See Note 1 and Note 10.

[9] See Note 6.

[10] Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6) and amounts charged by Anadarko under the omnibus agreements of the Partnership and WES Operating.

[11] Includes amounts related to the APCWH Note Payable (see Note 1 and Note 10).

[12] See Note 1.

[13] Represents distributions paid to Anadarko under the partnership agreement of the Partnership (see Note 4 and Note 5).

[14] Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to WES Operating by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6) and amounts charged by Anadarko under the omnibus agreement of WES Operating.

[15] Represents distributions paid to the Partnership and other subsidiaries of Anadarko under WES Operating’s partnership agreement (see Note 4 and Note 5). For the three months ended March 31, 2019, includes distributions to the Partnership and a subsidiary of Anadarko related to the repayment of the WGP RCF (see Note 10).

[16] Represents distributions paid to other subsidiaries of Anadarko under WES Operating’s partnership agreement (see Note 4 and Note 5).