Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Cash flows from operating activities
Net income (loss)		$ 573,202		$ 596,980		$ 11,098
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization		290,874		272,933		272,611
Impairments		178,374		15,535		515,458
Non-cash equity-based compensation expense		5,169		4,986		4,445
Deferred income taxes		2,458		2,555		11,346
Accretion and amortization of long-term obligations, net		4,932		(3,262)		17,698
Equity income, net – affiliates	[1]	(85,194)		(78,717)		(71,251)
Distributions from equity investment earnings – affiliates		87,380		82,185		82,054
(Gain) loss on divestiture and other, net	[2],[3]	(132,388)		14,641		(57,024)
Lower of cost or market inventory adjustments		145		168		443
Changes in assets and liabilities:
(Increase) decrease in accounts receivable, net		(16,195)		(48,998)		(4,428)
Increase (decrease) in accounts and imbalance payables and accrued liabilities, net		(6,919)		58,365		1,006
Change in other items, net		(4,426)		(4,295)		(647)
Net cash provided by operating activities		897,412		913,076		782,809
Cash flows from investing activities
Capital expenditures		(675,025)		(479,993)		(637,964)
Investments in equity affiliates		(384)		(27)		(11,442)
Distributions from equity investments in excess of cumulative earnings – affiliates		23,085	[4]	21,238	[4]	16,244
Proceeds from property insurance claims		22,977		17,465		0
Net cash used in investing activities		(763,604)		(1,105,534)		(500,277)
Cash flows from financing activities
Borrowings, net of debt issuance costs		369,989		1,323,198		889,606
Repayments of debt		0		(900,000)		(611,150)
Increase (decrease) in outstanding checks		5,593		2,079		(2,666)
Distributions to WGP unitholders	[5]	(441,967)		(374,082)		(306,477)
Net contributions from (distributions to) Anadarko		1,263		(23,491)		(49,801)
Above-market component of swap agreements with Anadarko	[5]	58,551		45,820		18,449
Net cash provided by (used in) financing activities		(413,292)		451,836		(250,051)
Net increase (decrease) in cash and cash equivalents		(279,484)		259,378		32,481
Cash and cash equivalents at beginning of period		359,072		99,694		67,213
Cash and cash equivalents at end of period		79,588		359,072		99,694
Supplemental disclosures
Accretion expense and revisions to the Deferred purchase price obligation – Anadarko	[6]	(4,094)		(147,234)		174,276
Net distributions to (contributions from) Anadarko of other assets	[7]	(3,189)		581		4,632
Interest paid, net of capitalized interest		138,871		107,657		94,720
Taxes paid (reimbursements received)		1,194		838		(138)
Accrued capital expenditures		204,309		79,253		61,454
Fair value of properties and equipment from non-cash third party transactions	[6]	551,453		0		0
Chipeta [Member]
Cash flows from financing activities
Distributions to Chipeta noncontrolling interest owner		(13,569)		(13,784)		(12,187)
Western Gas Partners, LP [Member]
Cash flows from financing activities
Proceeds from the issuance of WES common units, net of offering expenses		(183)		0		57,353
Distributions to noncontrolling interest owners of WES		(355,623)		(294,841)		(233,178)
Western Gas Partners, LP [Member] | Series A Preferred Units [Member]
Cash flows from financing activities
Proceeds from the issuance of WES Series A Preferred units, net of offering expenses		0		686,937		0
Affiliates [Member]
Cash flows from investing activities
Contributions in aid of construction costs from affiliates		1,387		6,135		461
Acquisitions		(3,910)		(716,465)		(10,903)
Proceeds from the sale of assets		0		623		925
Cash flows from financing activities
Settlement of the Deferred purchase price obligation - Anadarko	[6]	(37,346)		0		0
Distributions to WGP unitholders	[8]	(360,523)		(315,505)		(269,029)
Affiliates [Member] | Western Gas Partners, LP [Member]
Cash flows from financing activities
Distributions to WGP unitholders	[9]	(7,100)		(5,614)		(2,235)
Third Parties [Member]
Cash flows from investing activities
Acquisitions		(155,298)		0		(3,514)
Proceeds from the sale of assets		$ 23,564		$ 45,490		$ 145,916

[1] Represents amounts earned or incurred on and subsequent to the date of the 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] Includes losses related to an incident at the DBM complex for the years ended December 31, 2017 and 2015. See Note 1.

[3] Includes losses related to an incident at the DBM complex for the years ended December 31, 2017 and 2015. See Note 1.

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

[5] See Note 5.

[6] See Note 2.

[7] Includes $(1.4) million related to pipe and equipment purchases and $(1.8) million related to other assets for the year ended December 31, 2017. See Note 5.

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

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