Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Cash flows from operating activities
Net income	$ 387,379		$ 281,878		$ 120,557
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and impairments	183,156		145,916		120,608
Non-cash equity-based compensation expense	4,105		3,822		3,717
Deferred income taxes	2,583		31,891		(2,263)
Debt-related amortization and other items, net	2,736		2,449		2,319
Equity income, net	(57,836)	[1],[2],[3]	(22,948)	[1],[2],[3]	(16,042)	[1],[2],[3]
Distributions from equity investment earnings	62,967	[3]	17,698	[3]	20,660	[3]
Changes in assets and liabilities:
(Increase) decrease in accounts receivable, net	(4,112)		(34,148)		23,157
Increase (decrease) in accounts and natural gas imbalance payables and accrued liabilities, net	(53,477)		22,700		5,320
Change in other items, net	3,473		(4,478)		(552)
Net cash provided by operating activities	530,974		444,780		277,481
Cash flows from investing activities
Capital expenditures	(673,004)		(646,471)		(638,121)
Acquisitions			(78,129)
Investments in equity affiliates	(64,278)		(294,693)		(108,457)
Distributions from equity investments in excess of cumulative earnings	18,055	[3],[4]	4,438	[3],[4]	0	[3]
Net cash used in investing activities	(2,621,559)		(1,652,995)		(1,357,537)
Cash flows from financing activities
Borrowings, net of debt issuance costs	1,648,028		957,503		1,041,648
Repayments of debt	(650,000)		(710,000)		(549,000)
Increase (decrease) in outstanding checks	1,693		(1,763)		1,800
Proceeds from the issuance of common units, net of offering expenses	0		(2,367)		412,020
Distributions to WGP unitholders	(228,481)		(137,000)		0
Net contributions from Anadarko	23,788		208,907		245,418
Net cash provided by financing activities	2,044,713		898,744		1,276,053
Net increase (decrease) in cash and cash equivalents	(45,872)		(309,471)		195,997
Cash and cash equivalents at beginning of period	113,085		422,556		226,559
Cash and cash equivalents at end of period	67,213		113,085		422,556
Supplemental disclosures
Net distributions to Anadarko of other assets	10,733		5,855		15,296
Interest paid, net of capitalized interest	67,648		47,098		28,042
Taxes paid (reimbursements received)	(90)		552		495
Capital lease asset transfer	4,833	[5]	0	[5]	0	[5]
Western Gas Partners [Member]
Cash flows from financing activities
Proceeds from the issuance of common units, net of offering expenses	691,178		725,050		211,932
Distributions to noncontrolling interest owners of WES	(176,344)		(130,706)		(99,570)
Western Gas Partners [Member] | Class C Units [Member]
Cash flows from financing activities
Proceeds from the issuance of WES Class C units	750,000		0		0
Chipeta Processing Limited Liability Company [Member]
Cash flows from financing activities
Contributions from Chipeta noncontrolling interest owners (including Anadarko)	0		2,247		29,108
Distributions to Chipeta noncontrolling interest owners	(15,149)		(13,127)		(17,303)
Affiliated Entity [Member]
Cash flows from investing activities
Contributions in aid of construction costs from affiliates	183		617		0
Acquisitions	(379,193)		(476,711)		(611,719)
Proceeds from the sale of assets	0		85		760
Cash flows from financing activities
Contributions from Chipeta noncontrolling interest owners (including Anadarko)	0	[6]	0	[6]	12,588	[6]
Distributions to Chipeta noncontrolling interest owners	0	[6]	0	[6]	(6,528)	[6]
Affiliated Entity [Member] | Western Gas Partners [Member]
Cash flows from financing activities
Distributions to WGP unitholders	(1,747)	[7]	(755)	[7]	0	[7]
Third Parties [Member]
Cash flows from investing activities
Acquisitions	(1,523,327)		(240,274)		0
Proceeds from the sale of assets	$ 5		$ 14		$ 0

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

[2] 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.

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

[4] Distributions in excess of cumulative earnings, classified as investing cash flows in the consolidated statements of cash flows, is calculated on an individual investment basis.

[5] For the year ended December 31, 2014, represents transfers of $4.6 million from other long-term assets, associated with the capital lease components of a processing agreement. See Note 8.

[6] 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.

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