Consolidated Statements of Cash Flows - WES Operating - USD ($) $ in Thousands		3 Months Ended				12 Months Ended
		Mar. 31, 2019		Mar. 31, 2018		Dec. 31, 2018
Cash flows from operating activities
Net income (loss)		$ 211,979		$ 181,010	[1]
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization		113,946		84,790	[1]
Impairments		390		200	[1]	$ 230,600
Non-cash equity-based compensation expense		2,368		1,630	[1]
Deferred income taxes		4,065		24,219	[1]
Accretion and amortization of long-term obligations, net		1,511		2,103	[1]
Equity income, net – affiliates	[2]	(57,992)		(30,229)	[1]
Distributions from equity investment earnings – affiliates		54,221		31,576	[1]
(Gain) loss on divestiture and other, net		590		(116)	[1]
(Gain) loss on interest-rate swaps		35,638		0	[1]
Lower of cost or market inventory adjustments		7		143	[1]
Changes in assets and liabilities:
(Increase) decrease in accounts receivable, net		9,486		(29,632)	[1]
Increase (decrease) in accounts and imbalance payables and accrued liabilities, net		(55,529)		28,904	[1]
Change in other items, net		22,393		5,553	[1]
Net cash provided by operating activities		343,073		300,151	[1]
Cash flows from investing activities
Capital expenditures		(386,144)		(533,185)	[1]
Investments in equity affiliates		(36,543)	[3]	0	[1]
Distributions from equity investments in excess of cumulative earnings – affiliates		7,792	[4]	8,850	[1]
Net cash used in investing activities		(2,515,732)		(524,219)	[1]
Cash flows from financing activities
Borrowings, net of debt issuance costs	[5]	2,430,750		1,444,082	[1]
Repayments of debt	[6]	(467,595)		(630,000)	[1]
Increase (decrease) in outstanding checks		(5,890)		(6,684)	[1]
Distributions to unitholders	[7]	(131,910)		(120,140)	[1]
Net contributions from (distributions to) Anadarko		451,591		64,251	[1]
Above-market component of swap agreements with Anadarko	[7]	7,407		14,282	[1]
Net cash provided by (used in) financing activities		2,180,564		668,166	[1]
Net increase (decrease) in cash and cash equivalents		7,905		444,098	[1]
Cash and cash equivalents at beginning of period	[1]	92,142		79,588		79,588
Cash and cash equivalents at end of period		100,047		523,686	[1]	92,142	[1]
Supplemental disclosures
Interest paid, net of capitalized interest		76,871		25,949	[1]
Taxes paid (reimbursements received)		96		(87)	[1]
Accrued capital expenditures		203,509		367,095	[1]
Chipeta [Member]
Cash flows from financing activities
Distributions to Chipeta noncontrolling interest owner		(1,935)		(3,353)	[1]
Affiliates [Member]
Cash flows from investing activities
Acquisitions		(2,007,501)		0	[1]
Cash flows from financing activities
Borrowings, net of debt issuance costs		11,000		106,600
Repayments of debt		(439,600)
Distributions to unitholders	[8]	(102,654)		(98,000)
Third Parties [Member]
Cash flows from investing activities
Acquisitions		(93,303)		0	[1]
Proceeds from the sale of assets		(33)		116	[1]
WES Operating [Member]
Cash flows from operating activities
Net income (loss)		214,450		182,870	[1]
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization		113,946		84,790	[1]
Impairments		390		200	[1]
Non-cash equity-based compensation expense		2,116		1,563	[1]
Deferred income taxes		4,065		24,219	[1]
Accretion and amortization of long-term obligations, net		1,490		1,378	[1]
Equity income, net – affiliates		(57,992)		(30,229)	[1]
Distributions from equity investment earnings – affiliates		54,221		31,576	[1]
(Gain) loss on divestiture and other, net		590		(116)	[1]
(Gain) loss on interest-rate swaps		35,638		0	[1]
Lower of cost or market inventory adjustments		7		143	[1]
Changes in assets and liabilities:
(Increase) decrease in accounts receivable, net		7,974		(29,633)	[1]
Increase (decrease) in accounts and imbalance payables and accrued liabilities, net		(54,430)		28,672	[1]
Change in other items, net		21,577		5,398	[1]
Net cash provided by operating activities		344,042		300,831	[1]
Cash flows from investing activities
Capital expenditures		(386,144)		(533,185)	[1]
Investments in equity affiliates		(36,543)		0	[1]
Distributions from equity investments in excess of cumulative earnings – affiliates		7,792		8,850	[1]
Net cash used in investing activities		(2,515,732)		(524,219)	[1]
Cash flows from financing activities
Borrowings, net of debt issuance costs	[9]	2,430,750		1,444,090	[1]
Repayments of debt	[10]	(439,595)		(630,000)	[1]
Increase (decrease) in outstanding checks		(5,890)		(6,684)	[1]
Distributions to unitholders	[11]	(263,358)		(216,586)	[1]
Net contributions from (distributions to) Anadarko		451,591		64,251	[1]
Above-market component of swap agreements with Anadarko	[11]	7,407		14,282	[1]
Net cash provided by (used in) financing activities		2,178,970		666,000	[1]
Net increase (decrease) in cash and cash equivalents		7,280		442,612	[1]
Cash and cash equivalents at beginning of period	[1]	90,448		78,814		78,814
Cash and cash equivalents at end of period		97,728		521,426	[1]	$ 90,448	[1]
Supplemental disclosures
Interest paid, net of capitalized interest		76,637		25,606	[1]
Taxes paid (reimbursements received)		96		(87)	[1]
Accrued capital expenditures		203,509		367,095	[1]
WES Operating [Member] | Chipeta [Member]
Cash flows from financing activities
Distributions to Chipeta noncontrolling interest owner		(1,935)		(3,353)	[1]
WES Operating [Member] | Affiliates [Member]
Cash flows from investing activities
Acquisitions		(2,007,501)		0	[1]
Cash flows from financing activities
Borrowings, net of debt issuance costs		11,000		106,600
Repayments of debt		(439,600)
Distributions to unitholders	[12]	(164,902)		(124,164)
WES Operating [Member] | Third Parties [Member]
Cash flows from investing activities
Acquisitions		(93,303)		0	[1]
Proceeds from the sale of assets		$ (33)		$ 116	[1]

[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] Includes capitalized interest of $1.5 million related to the construction of the pipeline owned by Cactus II.

[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] For the three months ended March 31, 2019 and 2018, includes $11.0 million and $106.6 million of borrowings, respectively, under the APCWH Note Payable.

[6] For the three months ended March 31, 2019, includes a $439.6 million repayment to settle the APCWH Note Payable. See Note 6.

[7] See Note 6.

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

[9] For the three months ended March 31, 2019 and 2018, includes $11.0 million and $106.6 million of borrowings, respectively, under the APCWH Note Payable.

[10] For the three months ended March 31, 2019, includes a $439.6 million repayment to settle the APCWH Note Payable. See Note 6.

[11] See Note 6.

[12] 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).