Acquisitions and Divestitures - Impact of the Deferred Purchase Price Obligation - Anadarko Table (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Deferred purchase price obligation - Anadarko, present value	[1]	$ 0		$ 0		$ 41,440
Affiliates [Member]
Property, Plant and Equipment [Line Items]
Settlement of the Deferred purchase price obligation - Anadarko	[2]			(37,346)	$ 0
Affiliates [Member] | Deferred Purchase Price Obligation - Anadarko [Member]
Property, Plant and Equipment [Line Items]
Accretion expense	[3]	0	$ (1,173)	71	(12,097)
Settlement of the Deferred purchase price obligation - Anadarko	[4]	0	$ 0	(37,346)	$ 0
Western Gas Partners, LP [Member] | Affiliates [Member] | Delaware Basin JV Gathering LLC [Member] | Deferred Purchase Price Obligation - Anadarko [Member]
Property, Plant and Equipment [Line Items]
Deferred purchase price obligation - Anadarko, present value		0		0		41,440
Accretion expense	[5]			71
Revision to Deferred purchase price obligation – Anadarko	[6]			(4,165)
Settlement of the Deferred purchase price obligation - Anadarko				(37,346)
Deferred purchase price obligation - Anadarko, future value	[7]	$ 0		$ 0		$ 56,455

[1] See Note 2.

[2] See Note 2.

[3] See Note 2 for a discussion of the Deferred purchase price obligation - Anadarko.

[4] Represents the cash payment to Anadarko for the settlement of the Deferred purchase price obligation - Anadarko (see Note 2).

[5] Accretion expense was recorded as a charge to Interest expense in the consolidated statements of operations.

[6] Recorded as revisions within Common units in the consolidated balance sheet and consolidated statement of equity and partners’ capital.

[7] Calculated using Level 3 inputs.