Consolidated Statements of Cash Flows - WES Operating - USD ($) $ in Thousands		3 Months Ended						6 Months Ended				12 Months Ended
		Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018		Mar. 31, 2018		Jun. 30, 2019		Jun. 30, 2018		Dec. 31, 2018
Cash flows from operating activities
Net income (loss)		$ 175,058	$ 211,979	$ 67,167	[1]	$ 181,010	[1]	$ 387,037		$ 248,177	[1]
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization		121,117		88,488	[1]			235,063		173,278	[1]
Impairments		797		127,184	[1]			1,187		127,384	[1]	$ 230,600
Non-cash equity-based compensation expense								5,493		3,165	[1]
Deferred income taxes								4,885		48,858	[1]
Accretion and amortization of long-term obligations, net								2,848		3,376	[1]
Equity income, net – affiliates		(63,598)		(49,430)	[1]			(121,590)		(79,659)	[1]
Distributions from equity investment earnings – affiliates								115,483		65,525	[1]
(Gain) loss on divestiture and other, net		1,061		(170)	[1]			1,651		(286)	[1]
(Gain) loss on interest-rate swaps								94,585		0	[1]
Lower of cost or market inventory adjustments								169		151	[1]
Changes in assets and liabilities:
(Increase) decrease in accounts receivable, net								2,668		(8,572)	[1]
Increase (decrease) in accounts and imbalance payables and accrued liabilities, net								(81,198)		42,040	[1]
Change in other items, net								38,250		5,889	[1]
Net cash provided by operating activities								686,531		629,326	[1]
Cash flows from investing activities
Capital expenditures								(704,425)		(1,112,474)	[1]
Investments in equity affiliates								(77,333)		(27,490)	[1]
Distributions from equity investments in excess of cumulative earnings – affiliates								17,052		13,632	[1]
Net cash used in investing activities								(2,865,168)		(1,287,904)	[1]
Cash flows from financing activities
Borrowings, net of debt issuance costs	[2]							2,710,750		1,525,439	[1]
Repayments of debt	[3]							(467,595)		(630,000)	[1]
Increase (decrease) in outstanding checks								(5,662)		(5,357)	[1]
Distributions to unitholders	[4]							(408,234)		(244,658)	[1]
Net contributions from (distributions to) Anadarko								456,938		157,264	[1]
Above-market component of swap agreements with Anadarko		0		13,839				7,407	[4]	28,121	[1],[4]
Net cash provided by (used in) financing activities								2,182,290		634,307	[1]
Net increase (decrease) in cash and cash equivalents								3,653		(24,271)	[1]
Cash and cash equivalents at beginning of period	[1]		92,142			79,588		92,142		79,588		79,588
Cash and cash equivalents at end of period		95,795		55,317	[1]			95,795		55,317	[1]	92,142	[1]
Supplemental disclosures
Interest paid, net of capitalized interest								137,686		56,784	[1]
Taxes paid (reimbursements received)								96		(87)	[1]
Accrued capital expenditures								141,094		327,777	[1]
Chipeta [Member]
Cash flows from financing activities
Distributions to Chipeta noncontrolling interest owner								(3,793)		(6,421)	[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		187,900
Repayments of debt								(439,600)
Distributions to unitholders		(153,231)		(101,571)				(255,885)		(199,571)
Third Parties [Member]
Cash flows from investing activities
Acquisitions								(93,303)		(161,858)	[1]
Proceeds from the sale of assets								342		286	[1]
WES Operating [Member]
Cash flows from operating activities
Net income (loss)		176,979	214,450	68,123	[1]	182,870	[1]	391,429		250,993	[1]
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization		121,117		88,488	[1]			235,063		173,278	[1]
Impairments		797		127,184	[1]			1,187		127,384	[1]
Non-cash equity-based compensation expense								4,882		3,017	[1]
Deferred income taxes								4,885		48,858	[1]
Accretion and amortization of long-term obligations, net								2,827		2,626	[1]
Equity income, net – affiliates		(63,598)		(49,430)	[1]			(121,590)		(79,659)	[1]
Distributions from equity investment earnings – affiliates								115,483		65,525	[1]
(Gain) loss on divestiture and other, net		1,061		(170)	[1]			1,651		(286)	[1]
(Gain) loss on interest-rate swaps								94,585		0	[1]
Lower of cost or market inventory adjustments								169		151	[1]
Changes in assets and liabilities:
(Increase) decrease in accounts receivable, net								2,464		(8,563)	[1]
Increase (decrease) in accounts and imbalance payables and accrued liabilities, net								(80,458)		42,088	[1]
Change in other items, net								38,069		5,578	[1]
Net cash provided by operating activities								690,646		630,990	[1]
Cash flows from investing activities
Capital expenditures								(704,425)		(1,112,474)	[1]
Investments in equity affiliates								(77,333)		(27,490)	[1]
Distributions from equity investments in excess of cumulative earnings – affiliates								17,052		13,632	[1]
Net cash used in investing activities								(2,865,168)		(1,287,904)	[1]
Cash flows from financing activities
Borrowings, net of debt issuance costs	[5]							2,710,750		1,525,447	[1]
Repayments of debt	[6]							(439,595)		(630,000)	[1]
Increase (decrease) in outstanding checks								(5,662)		(5,357)	[1]
Distributions to unitholders	[7]							(546,629)		(437,719)	[1]
Net contributions from (distributions to) Anadarko								456,938		157,264	[1]
Above-market component of swap agreements with Anadarko	[7]							7,407		28,121	[1]
Net cash provided by (used in) financing activities								2,179,416		631,335	[1]
Net increase (decrease) in cash and cash equivalents								4,894		(25,579)	[1]
Cash and cash equivalents at beginning of period	[1]		$ 90,448			$ 78,814		90,448		78,814		78,814
Cash and cash equivalents at end of period		95,342		53,235	[1]			95,342		53,235	[1]	$ 90,448	[1]
Supplemental disclosures
Interest paid, net of capitalized interest								137,452		56,155	[1]
Taxes paid (reimbursements received)								96		(87)	[1]
Accrued capital expenditures								141,094		327,777	[1]
WES Operating [Member] | Chipeta [Member]
Cash flows from financing activities
Distributions to Chipeta noncontrolling interest owner								(3,793)		(6,421)	[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		187,900
Repayments of debt								(439,600)
Distributions to unitholders		$ (283,271)		$ (127,204)				(448,173)		(251,368)
WES Operating [Member] | Third Parties [Member]
Cash flows from investing activities
Acquisitions								(93,303)		(161,858)	[1]
Proceeds from the sale of assets								$ 342		$ 286	[1]

[1] Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.

[2] For the six months ended June 30, 2019 and 2018, includes $11.0 million and $187.9 million of borrowings, respectively, under the APCWH Note Payable.

[3] For the six months ended June 30, 2019, includes a $439.6 million repayment to settle the APCWH Note Payable. See Note 6.

[4] See Note 6.

[5] For the six months ended June 30, 2019 and 2018, includes $11.0 million and $187.9 million of borrowings, respectively, under the APCWH Note Payable.

[6] For the six months ended June 30, 2019, includes a $439.6 million repayment to settle the APCWH Note Payable. See Note 6.

[7] See Note 6.