Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Cash flows from operating activities
Net income	$ 51,676		$ 45,628	[1]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and impairments	32,440		27,067	[1]
Non-cash equity-based compensation expense	858		914	[1]
Deferred income taxes	1,124		291	[1]
Debt-related amortization and other items, net	560		511	[1]
Changes in assets and liabilities:
(Increase) decrease in accounts receivable, net	21,439		32,704	[1]
Increase (decrease) in accounts and natural gas imbalance payables and accrued liabilities, net	22,469		(13,665)	[1]
Change in other items, net	(1,405)		1,083	[1]
Net cash provided by operating activities	129,161		94,533	[1]
Cash flows from investing activities
Capital expenditures	(166,463)		(75,837)	[1]
Investments in equity affiliates	(4,835)
Net cash used in investing activities	(771,888)		(539,069)	[1]
Cash flows from financing activities
Borrowings, net of debt issuance costs	384,946		319,000	[1]
Repayments of debt			(40,000)	[1]
Increase (decrease) in outstanding checks	(2,808)		4,919	[1]
Offering expenses from the issuance of WGP common units	(2,367)
Distributions to unitholders	(7,852)
Net distributions to Anadarko	(29,942)		(8,873)	[1]
Net cash provided by financing activities	311,635		257,595	[1]
Net increase (decrease) in cash and cash equivalents	(331,092)		(186,941)	[1]
Cash and cash equivalents at beginning of period	422,556	[1]	226,559	[1]
Cash and cash equivalents at end of period	91,464		39,618	[1]
Supplemental disclosures
Net contributions from Anadarko of other assets	(6)
Net distributions to Anadarko of other assets			3,000	[1]
Interest paid, net of capitalized interest	11,244		1,986	[1]
Taxes paid			72	[1]
Affiliated Entity Member
Cash flows from investing activities
Acquisitions	(465,721)		(463,232)	[1]
Third Parties [Member]
Cash flows from investing activities
Acquisitions	(134,869)
Chipeta Processing Limited Liability Company [Member]
Cash flows from financing activities
Contributions received from Chipeta noncontrolling interest owners (including Anadarko)	1,097		9,849	[1]
Distributions to noncontrolling interest owners (including Anadarko)	(2,650)		(5,145)	[1]
Western Gas Equity Partners [Member]
Cash flows from financing activities
Distributions to noncontrolling interest owners (including Anadarko)	$ (28,789)		$ (22,155)	[1]

[1] Financial information has been recast to include the financial position and results attributable to the Non-Operated Marcellus Interest. See Note 2.