Western Midstream Partners 10-Q 1 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 29, 2019
Entity Information [Line Items]
Trading Symbol	WES
Entity Registrant Name	Western Midstream Partners, LP
Entity Central Index Key	0001423902
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Units Outstanding		452,990,862
Entity Emerging Growth Company	false
Entity Small Business	false
WES Operating [Member]
Entity Information [Line Items]
Entity Registrant Name	Western Midstream Operating, LP
Entity Central Index Key	0001414475
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Units Outstanding		0
Entity Emerging Growth Company	false
Entity Small Business	false

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands		3 Months Ended			12 Months Ended
		Mar. 31, 2019	Mar. 31, 2018		Dec. 31, 2018
Revenues and Other
Revenues and other		$ 671,883	$ 501,054	[1]
Equity income, net – affiliates	[2]	57,992	30,229	[1]
Operating expenses
Cost of product	[3]	114,063	94,318	[1]
Operation and maintenance	[3]	142,829	96,795	[1]
General and administrative	[3]	22,844	15,829	[1]
Property and other taxes		16,285	14,600	[1]
Depreciation and amortization		113,946	84,790	[1]
Impairments		390	200	[1]	$ 230,600
Total operating expenses		410,357	306,532	[1]
Gain (loss) on divestiture and other, net		(590)	116	[1]
Operating income (loss)		318,928	224,867	[1]
Interest income – affiliates	[4]	4,225	4,225	[1]
Interest expense	[5]	(65,876)	(38,015)	[1]
Other income (expense), net		(35,206)	817	[1]
Income (loss) before income taxes		222,071	191,894	[1]
Income tax expense (benefit)		10,092	10,884	[1]
Net income (loss)		211,979	181,010	[1]
Net income (loss) attributable to noncontrolling interests		93,319	49,483	[1]
Net income (loss) attributable to Western Midstream Partners, LP		118,660	131,527	[1]
Limited partners' interest in net income (loss):
Pre-acquisition net (income) loss allocated to Anadarko		(29,116)	(30,522)	[1]
Limited partners' interest in net income (loss)		89,544	101,005	[1]
Affiliates [Member]
Revenues and Other
Revenues and other	[2]	378,437	285,176	[1]
Operating expenses
Cost of product	[2]	56,172	34,819
Operation and maintenance	[2]	39,141	23,001
General and administrative	[6]	18,894	12,688
Total operating expenses		114,207	70,508
Interest expense	[7]	(1,833)	(577)
Affiliates [Member] | Service Revenues - Fee Based [Member]
Revenues and Other
Revenues and other		326,642	222,038	[1]
Affiliates [Member] | Service Revenues - Product Based [Member]
Revenues and Other
Revenues and other		1,352	631	[1]
Affiliates [Member] | Product Sales [Member]
Revenues and Other
Revenues and other		50,443	62,507	[1]
Third Parties [Member]
Revenues and Other
Revenues and other		293,446	215,878	[1]
Operating expenses
Interest expense		(64,043)	(37,438)
Third Parties [Member] | Service Revenues - Fee Based [Member]
Revenues and Other
Revenues and other		253,332	171,735	[1]
Third Parties [Member] | Service Revenues - Product Based [Member]
Revenues and Other
Revenues and other		18,027	22,792	[1]
Third Parties [Member] | Product Sales [Member]
Revenues and Other
Revenues and other		21,690	21,118	[1]
Third Parties [Member] | Other [Member]
Revenues and Other
Revenues and other		$ 397	$ 233	[1]
Limited Partner [Member]
Limited partners' interest in net income (loss):
Net income (loss) per common unit - basic and diluted		$ 0.30	$ 0.46	[1]
Weighted-average common units outstanding - basic and diluted		299,556	218,933	[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]	Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.9 million and $12.7 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.
[4]	Represents interest income recognized on the note receivable from Anadarko.
[5]	Includes affiliate (as defined in Note 1) amounts of $1.8 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively. See Note 1 and Note 10.
[6]	Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6) and amounts charged by Anadarko under the omnibus agreements of the Partnership and WES Operating.
[7]	Includes amounts related to the APCWH Note Payable (see Note 1 and Note 10).

Consolidated Statements of Op_2

Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Cost of product	[1]	$ 114,063	$ 94,318	[2]
Operation and maintenance	[1]	142,829	96,795	[2]
General and administrative	[1]	22,844	15,829	[2]
Interest expense	[3]	65,876	38,015	[2]
Affiliates [Member]
Cost of product	[4]	56,172	34,819
Operation and maintenance	[4]	39,141	23,001
General and administrative	[5]	18,894	12,688
Interest expense	[6]	$ 1,833	$ 577
[1]	Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.9 million and $12.7 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.
[2]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[3]	Includes affiliate (as defined in Note 1) amounts of $1.8 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively. See Note 1 and Note 10.
[4]	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.
[5]	Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6) and amounts charged by Anadarko under the omnibus agreements of the Partnership and WES Operating.
[6]	Includes amounts related to the APCWH Note Payable (see Note 1 and Note 10).

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018	[1]	Mar. 31, 2018	[1]	Dec. 31, 2017	[1]
Current assets
Cash and cash equivalents		$ 100,047	$ 92,142		$ 523,686		$ 79,588
Accounts receivable, net	[2]	212,423	221,164
Other current assets	[3]	23,472	27,056
Total current assets		335,942	340,362
Note receivable - Anadarko		260,000	260,000
Property, plant and equipment
Cost		11,580,329	11,258,773
Less accumulated depreciation		2,950,330	2,848,420
Net property, plant and equipment		8,629,999	8,410,353
Goodwill		445,800	445,800
Other intangible assets		833,404	841,408
Equity investments		1,217,156	1,092,088
Other assets	[4]	74,694	67,194
Total assets		11,796,995	11,457,205
Current liabilities
Accounts and imbalance payables		328,867	443,343
Short-term debt		2,000,000	28,000
Accrued ad valorem taxes		48,545	36,986
Accrued liabilities	[5]	141,442	129,148
Total current liabilities		2,518,854	637,477
Long-term liabilities
Long-term debt		5,208,411	4,787,381
APCWH Note Payable	[6]	0	427,493
Deferred income taxes		15,355	280,017
Asset retirement obligations		311,716	300,024
Other liabilities	[7]	151,118	132,130
Total long-term liabilities		5,686,600	5,927,045
Total liabilities		8,205,454	6,564,522
Equity and partners' capital
Common units (452,990,862 and 218,937,797 units issued and outstanding at March 31, 2019, and December 31, 2018, respectively)		3,437,922	951,888
Net investment by Anadarko		0	1,388,018
Total partners' capital		3,437,922	2,339,906
Noncontrolling interests		153,619	2,552,777
Total equity and partners' capital		3,591,541	4,892,683		$ 4,994,493		$ 4,995,050
Total liabilities, equity and partners' capital		$ 11,796,995	$ 11,457,205
[1]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[2]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $68.5 million and $72.6 million as of March 31, 2019, and December 31, 2018, respectively.
[3]	Other current assets includes affiliate amounts of $7.4 million and $3.7 million as of March 31, 2019, and December 31, 2018, respectively.
[4]	Other assets includes affiliate amounts of $42.9 million and $42.2 million as of March 31, 2019, and December 31, 2018, respectively.
[5]	Accrued liabilities includes affiliate amounts of $3.5 million and $2.2 million as of March 31, 2019, and December 31, 2018, respectively.
[6]	See Note 1 and Note 6.
[7]	Other liabilities includes affiliate amounts of $60.6 million and $47.8 million as of March 31, 2019, and December 31, 2018, respectively.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Common units issued		452,990,862	218,937,797
Common units outstanding		452,990,862	218,937,797
Accounts receivable, net	[1]	$ 212,423	$ 221,164	[2]
Other current assets	[3]	23,472	27,056	[2]
Other assets	[4]	74,694	67,194	[2]
Accrued liabilities	[5]	141,442	129,148	[2]
Other liabilities	[6]	151,118	132,130	[2]
Affiliates [Member]
Accounts receivable, net		68,500	72,600
Other current assets		7,400	3,700
Other assets		42,900	42,200
Accrued liabilities		3,500	2,200
Other liabilities		$ 60,600	$ 47,800
[1]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $68.5 million and $72.6 million as of March 31, 2019, and December 31, 2018, respectively.
[2]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[3]	Other current assets includes affiliate amounts of $7.4 million and $3.7 million as of March 31, 2019, and December 31, 2018, respectively.
[4]	Other assets includes affiliate amounts of $42.9 million and $42.2 million as of March 31, 2019, and December 31, 2018, respectively.
[5]	Accrued liabilities includes affiliate amounts of $3.5 million and $2.2 million as of March 31, 2019, and December 31, 2018, respectively.
[6]	Other liabilities includes affiliate amounts of $60.6 million and $47.8 million as of March 31, 2019, and December 31, 2018, respectively.

Consolidated Statements of Equi

Consolidated Statements of Equity and Partners' Capital - USD ($) $ in Thousands		Total	Chipeta [Member]	WES Operating [Member]	Net Investment by Anadarko [Member]	Common Units [Member]	Noncontrolling Interests [Member]	Noncontrolling Interests [Member]Chipeta [Member]	Noncontrolling Interests [Member]WES Operating [Member]
Balance at Dec. 31, 2017	[1]	$ 4,995,050			$ 1,050,171	$ 1,061,125	$ 2,883,754
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income (loss)	[1]	181,010			30,522	101,005	49,483
Above-market component of swap agreements with Anadarko	[1],[2]	14,282				14,282
WES Operating equity transactions, net	[1],[3]	0				(2,525)	2,525
Distributions to noncontrolling interest owners	[1]		$ (3,353)	$ (94,272)				$ (3,353)	$ (94,272)
Distributions to Partnership unitholders	[1]	(120,140)				(120,140)
Contributions of equity-based compensation from Anadarko	[1]	1,470				1,470
Net pre-acquisition contributions from (distributions to) Anadarko	[1]	64,251			64,251
Adjustments of net deferred tax liabilities	[1]	(175)			(175)
Other	[1]	150				58	92
Balance at Mar. 31, 2018	[1]	4,994,493			1,145,398	1,041,066	2,808,029
Increase (Decrease) in Partners' Capital [Roll Forward]
Cumulative effect of accounting change	[1]	(43,780)			629	(14,209)	(30,200)
Balance at Dec. 31, 2018	[1]	4,892,683			1,388,018	951,888	2,552,777
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income (loss)		211,979			29,116	89,544	93,319
Cumulative impact of the Merger transactions	[4]	0				3,169,800	(3,169,800)
Above-market component of swap agreements with Anadarko	[5]	7,407				7,407
WES Operating equity transactions, net	[6]	0				(752,796)	752,796
Distributions to noncontrolling interest owners			$ (1,935)	$ (100,999)				$ (1,935)	$ (100,999)
Distributions to Partnership unitholders		(131,910)				(131,910)
Acquisitions from affiliates	[7]	(2,007,501)			(2,141,827)	106,856	27,470
Contributions of equity-based compensation from Anadarko		1,840				1,840
Net pre-acquisition contributions from (distributions to) Anadarko		451,591			451,591
Adjustments of net deferred tax liabilities		268,727			273,102	(4,375)
Other		(341)				(332)	(9)
Balance at Mar. 31, 2019		$ 3,591,541			$ 0	$ 3,437,922	$ 153,619
[1]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[2]	See Note 6.
[3]	The $2.5 million decrease to partners’ capital, together with net income (loss) attributable to Western Midstream Partners, LP, totaled $129.0 million for the three months ended March 31, 2018.
[4]	See Note 1.
[5]	See Note 6.
[6]	The $752.8 million decrease to partners’ capital, together with net income (loss) attributable to Western Midstream Partners, LP, totaled $(634.1) million for the three months ended March 31, 2019.
[7]	The amounts allocated to common unitholders and noncontrolling interests represent a noncash investing activity related to the assets and liabilities assumed in the AMA acquisition.

Consolidated Statements of Eq_2

Consolidated Statements of Equity and Partners' Capital (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019		Mar. 31, 2018
WES Operating equity transactions, net	$ 0	[1]	$ 0	[2],[3]
Combined change in Partners' Capital from WES Operating equity transactions, net and net income (loss) attributable to Western Midstream Partners, LP	(634,100)		129,000
Common Units [Member]
WES Operating equity transactions, net	$ (752,796)	[1]	$ (2,525)	[2],[3]
[1]	The $752.8 million decrease to partners’ capital, together with net income (loss) attributable to Western Midstream Partners, LP, totaled $(634.1) million for the three months ended March 31, 2019.
[2]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[3]	The $2.5 million decrease to partners’ capital, together with net income (loss) attributable to Western Midstream Partners, LP, totaled $129.0 million for the three months ended March 31, 2018.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019		Mar. 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]
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]
Registration expenses related to the issuance of WES common units		(855)		0	[1]
Distributions to WES 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
Cash and cash equivalents at end of period		100,047		523,686	[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]
WES Operating [Member]
Cash flows from financing activities
Distributions to noncontrolling interest owner		100,999		94,272	[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 WES unitholders	[8]	102,654		98,000
Affiliates [Member] | WES Operating [Member]
Cash flows from financing activities
Distributions to WES unitholders	[9]	2,543		1,850
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]	Represents distributions paid to other subsidiaries of Anadarko under WES Operating’s partnership agreement (see Note 4 and Note 5).

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Borrowings, net of debt issuance costs	[1]	$ 2,430,750	$ 1,444,082	[2]
Repayments of debt	[3]	467,595	630,000	[2]
Affiliates [Member]
Borrowings, net of debt issuance costs		11,000	$ 106,600
Repayments of debt		$ 439,600
[1]	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.
[2]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[3]	For the three months ended March 31, 2019, includes a $439.6 million repayment to settle the APCWH Note Payable. See Note 6.

Consolidated Statements of Op_3

Consolidated Statements of Operations - WES Operating - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Revenues and Other
Revenues and other		$ 671,883	$ 501,054	[1]
Equity income, net – affiliates	[2]	57,992	30,229	[1]
Operating expenses
Cost of product	[3]	114,063	94,318	[1]
Operation and maintenance	[3]	142,829	96,795	[1]
General and administrative	[3]	22,844	15,829	[1]
Property and other taxes		16,285	14,600	[1]
Depreciation and amortization		113,946	84,790	[1]
Impairments		390	200	[1]
Total operating expenses		410,357	306,532	[1]
Gain (loss) on divestiture and other, net		(590)	116	[1]
Operating income (loss)		318,928	224,867	[1]
Interest income – affiliates	[4]	4,225	4,225	[1]
Interest expense	[5]	(65,876)	(38,015)	[1]
Other income (expense), net		(35,206)	817	[1]
Income (loss) before income taxes		222,071	191,894	[1]
Income tax expense (benefit)		10,092	10,884	[1]
Net income (loss)		211,979	181,010	[1]
Net income (loss) attributable to noncontrolling interest		93,319	49,483	[1]
Net income (loss) attributable to Western Midstream Operating, LP		118,660	131,527	[1]
Limited partners' interest in net income (loss):
Pre-acquisition net (income) loss allocated to Anadarko		(29,116)	(30,522)	[1]
Limited partners' interest in net income (loss)		89,544	101,005	[1]
Affiliates [Member]
Revenues and Other
Revenues and other	[2]	378,437	285,176	[1]
Operating expenses
Cost of product	[2]	56,172	34,819
Operation and maintenance	[2]	39,141	23,001
General and administrative	[6]	18,894	12,688
Total operating expenses		114,207	70,508
Interest expense	[7]	(1,833)	(577)
Affiliates [Member] | Service Revenues - Fee Based [Member]
Revenues and Other
Revenues and other		326,642	222,038	[1]
Affiliates [Member] | Service Revenues - Product Based [Member]
Revenues and Other
Revenues and other		1,352	631	[1]
Affiliates [Member] | Product Sales [Member]
Revenues and Other
Revenues and other		50,443	62,507	[1]
Third Parties [Member]
Revenues and Other
Revenues and other		293,446	215,878	[1]
Operating expenses
Interest expense		(64,043)	(37,438)
Third Parties [Member] | Service Revenues - Fee Based [Member]
Revenues and Other
Revenues and other		253,332	171,735	[1]
Third Parties [Member] | Service Revenues - Product Based [Member]
Revenues and Other
Revenues and other		18,027	22,792	[1]
Third Parties [Member] | Product Sales [Member]
Revenues and Other
Revenues and other		21,690	21,118	[1]
Third Parties [Member] | Other [Member]
Revenues and Other
Revenues and other		397	233	[1]
WES Operating [Member]
Revenues and Other
Revenues and other		671,883	501,054	[1]
Equity income, net – affiliates		57,992	30,229	[1]
Operating expenses
Cost of product	[8]	114,063	94,318	[1]
Operation and maintenance	[8]	142,829	96,795	[1]
General and administrative	[8]	20,560	14,997	[1]
Property and other taxes		16,285	14,600	[1]
Depreciation and amortization		113,946	84,790	[1]
Impairments		390	200	[1]
Total operating expenses		408,073	305,700	[1]
Gain (loss) on divestiture and other, net		(590)	116	[1]
Operating income (loss)		321,212	225,699	[1]
Interest income – affiliates	[4]	4,225	4,225	[1]
Interest expense	[9]	(65,631)	(36,952)	[1]
Other income (expense), net		(35,264)	782	[1]
Income (loss) before income taxes		224,542	193,754	[1]
Income tax expense (benefit)		10,092	10,884	[1]
Net income (loss)		214,450	182,870	[1]
Net income (loss) attributable to noncontrolling interest		1,854	2,985	[1]
Net income (loss) attributable to Western Midstream Operating, LP		212,596	179,885	[1]
Limited partners' interest in net income (loss):
Pre-acquisition net (income) loss allocated to Anadarko		(29,116)	(30,522)	[1]
General partner interest in net (income) loss	[10]	0	(83,439)	[1]
WES Operating [Member] | Common and Class C Units [Member]
Limited partners' interest in net income (loss):
Limited partners' interest in net income (loss)	[10]	183,480	65,924	[1]
WES Operating [Member] | Affiliates [Member]
Revenues and Other
Revenues and other		378,437	285,176	[1]
Operating expenses
Cost of product	[2]	56,172	34,819
Operation and maintenance	[2]	39,141	23,001
General and administrative	[11]	18,498	12,479
Interest expense	[7]	(1,833)	(577)
WES Operating [Member] | Affiliates [Member] | Service Revenues - Fee Based [Member]
Revenues and Other
Revenues and other		326,642	222,038	[1]
WES Operating [Member] | Affiliates [Member] | Service Revenues - Product Based [Member]
Revenues and Other
Revenues and other		1,352	631	[1]
WES Operating [Member] | Affiliates [Member] | Product Sales [Member]
Revenues and Other
Revenues and other		50,443	62,507	[1]
WES Operating [Member] | Third Parties [Member]
Revenues and Other
Revenues and other		293,446	215,878	[1]
WES Operating [Member] | Third Parties [Member] | Service Revenues - Fee Based [Member]
Revenues and Other
Revenues and other		253,332	171,735	[1]
WES Operating [Member] | Third Parties [Member] | Service Revenues - Product Based [Member]
Revenues and Other
Revenues and other		18,027	22,792	[1]
WES Operating [Member] | Third Parties [Member] | Product Sales [Member]
Revenues and Other
Revenues and other		21,690	21,118	[1]
WES Operating [Member] | Third Parties [Member] | Other [Member]
Revenues and Other
Revenues and other		$ 397	233	[1]
Common Units [Member] | WES Operating [Member]
Limited partners' interest in net income (loss):
Limited partners' interest in net income (loss)	[12]		$ 58,323
Net income (loss) per common unit - basic and diluted	[1],[10],[13]		$ 0.38
[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]	Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.9 million and $12.7 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.
[4]	Represents interest income recognized on the note receivable from Anadarko.
[5]	Includes affiliate (as defined in Note 1) amounts of $1.8 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively. See Note 1 and Note 10.
[6]	Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6) and amounts charged by Anadarko under the omnibus agreements of the Partnership and WES Operating.
[7]	Includes amounts related to the APCWH Note Payable (see Note 1 and Note 10).
[8]	Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.5 million and $12.5 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.
[9]	Includes affiliate (as defined in Note 1) amounts of $1.8 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively. See Note 1 and Note 10.
[10]	See Note 5 for the calculation of net income (loss) per common unit.
[11]	Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to WES Operating by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6) and amounts charged by Anadarko under the omnibus agreement of WES Operating.
[12]	Adjusted to reflect amortization of the beneficial conversion feature.
[13]	The impact of Class C units would be anti-dilutive for the period presented.

Consolidated Statements of Op_4

Consolidated Statements of Operations - WES Operating (Parenthetical) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Cost of product	[1]	$ 114,063	$ 94,318	[2]
Operation and maintenance	[1]	142,829	96,795	[2]
General and administrative	[1]	22,844	15,829	[2]
Interest expense	[3]	65,876	38,015	[2]
Affiliates [Member]
Cost of product	[4]	56,172	34,819
Operation and maintenance	[4]	39,141	23,001
General and administrative	[5]	18,894	12,688
Interest expense	[6]	1,833	577
WES Operating [Member]
Cost of product	[7]	114,063	94,318	[2]
Operation and maintenance	[7]	142,829	96,795	[2]
General and administrative	[7]	20,560	14,997	[2]
Interest expense	[8]	65,631	36,952	[2]
WES Operating [Member] | Affiliates [Member]
Cost of product	[4]	56,172	34,819
Operation and maintenance	[4]	39,141	23,001
General and administrative	[9]	18,498	12,479
Interest expense	[6]	$ 1,833	$ 577
[1]	Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.9 million and $12.7 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.
[2]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[3]	Includes affiliate (as defined in Note 1) amounts of $1.8 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively. See Note 1 and Note 10.
[4]	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.
[5]	Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6) and amounts charged by Anadarko under the omnibus agreements of the Partnership and WES Operating.
[6]	Includes amounts related to the APCWH Note Payable (see Note 1 and Note 10).
[7]	Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.5 million and $12.5 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.
[8]	Includes affiliate (as defined in Note 1) amounts of $1.8 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively. See Note 1 and Note 10.
[9]	Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to WES Operating by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6) and amounts charged by Anadarko under the omnibus agreement of WES Operating.

Consolidated Balance Sheets - W

Consolidated Balance Sheets - WES Operating - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018	[1]
Current assets
Cash and cash equivalents		$ 100,047	$ 92,142
Accounts receivable, net	[2]	212,423	221,164
Other current assets	[3]	23,472	27,056
Total current assets		335,942	340,362
Note receivable - Anadarko		260,000	260,000
Property, plant and equipment
Cost		11,580,329	11,258,773
Less accumulated depreciation		2,950,330	2,848,420
Net property, plant and equipment		8,629,999	8,410,353
Goodwill		445,800	445,800
Other intangible assets		833,404	841,408
Equity investments		1,217,156	1,092,088
Other assets	[4]	74,694	67,194
Total assets		11,796,995	11,457,205
Current liabilities
Accounts and imbalance payables		328,867	443,343
Short-term debt		2,000,000	28,000
Accrued ad valorem taxes		48,545	36,986
Accrued liabilities	[5]	141,442	129,148
Total current liabilities		2,518,854	637,477
Long-term liabilities
Long-term debt		5,208,411	4,787,381
APCWH Note Payable	[6]	0	427,493
Deferred income taxes		15,355	280,017
Asset retirement obligations		311,716	300,024
Other liabilities	[7]	151,118	132,130
Total long-term liabilities		5,686,600	5,927,045
Total liabilities		8,205,454	6,564,522
Equity and partners' capital
Common units and Class C units		3,437,922	951,888
Net investment by Anadarko		0	1,388,018
Total partners' capital		3,437,922	2,339,906
Noncontrolling interest		153,619	2,552,777
Total equity and partners' capital		3,591,541	4,892,683
Total liabilities, equity and partners' capital		11,796,995	11,457,205
WES Operating [Member]
Current assets
Cash and cash equivalents		97,728	90,448
Accounts receivable, net	[8]	214,148	221,373
Other current assets	[9]	23,434	26,181
Total current assets		335,310	338,002
Note receivable - Anadarko		260,000	260,000
Property, plant and equipment
Cost		11,580,329	11,258,773
Less accumulated depreciation		2,950,330	2,848,420
Net property, plant and equipment		8,629,999	8,410,353
Goodwill		445,800	445,800
Other intangible assets		833,404	841,408
Equity investments		1,217,156	1,092,088
Other assets	[10]	74,694	67,194
Total assets		11,796,363	11,454,845
Current liabilities
Accounts and imbalance payables		328,867	443,343
Short-term debt		2,000,000	0
Accrued ad valorem taxes		48,545	36,986
Accrued liabilities	[11]	141,267	127,874
Total current liabilities		2,518,679	608,203
Long-term liabilities
Long-term debt		5,208,411	4,787,381
APCWH Note Payable	[12]	0	427,493
Deferred income taxes		15,355	280,017
Asset retirement obligations		311,716	300,024
Other liabilities	[13]	151,118	132,130
Total long-term liabilities		5,686,600	5,927,045
Total liabilities		8,205,279	6,535,248
Equity and partners' capital
General partner units (zero and 2,583,068 units issued and outstanding at March 31, 2019, and December 31, 2018, respectively)	[14]	0	206,862
Net investment by Anadarko		0	1,388,018
Total partners' capital		3,533,398	4,861,830
Noncontrolling interest		57,686	57,767
Total equity and partners' capital		3,591,084	4,919,597
Total liabilities, equity and partners' capital		11,796,363	11,454,845
WES Operating [Member] | Common Units [Member]
Equity and partners' capital
Common units and Class C units		3,533,398	2,475,540
WES Operating [Member] | Class C Units [Member]
Equity and partners' capital
Common units and Class C units	[14]	$ 0	$ 791,410
[1]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[2]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $68.5 million and $72.6 million as of March 31, 2019, and December 31, 2018, respectively.
[3]	Other current assets includes affiliate amounts of $7.4 million and $3.7 million as of March 31, 2019, and December 31, 2018, respectively.
[4]	Other assets includes affiliate amounts of $42.9 million and $42.2 million as of March 31, 2019, and December 31, 2018, respectively.
[5]	Accrued liabilities includes affiliate amounts of $3.5 million and $2.2 million as of March 31, 2019, and December 31, 2018, respectively.
[6]	See Note 1 and Note 6.
[7]	Other liabilities includes affiliate amounts of $60.6 million and $47.8 million as of March 31, 2019, and December 31, 2018, respectively.
[8]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $70.2 million and $72.8 million as of March 31, 2019, and December 31, 2018, respectively.
[9]	Other current assets includes affiliate amounts of $7.4 million and $3.7 million as of March 31, 2019, and December 31, 2018, respectively.
[10]	Other assets includes affiliate amounts of $42.9 million and $42.2 million as of March 31, 2019, and December 31, 2018, respectively.
[11]	Accrued liabilities includes affiliate amounts of $3.5 million and $2.2 million as of March 31, 2019, and December 31, 2018, respectively.
[12]	See Note 1 and Note 6.
[13]	Other liabilities includes affiliate amounts of $60.6 million and $47.8 million as of March 31, 2019, and December 31, 2018, respectively.
[14]	Immediately prior to the closing of the Merger (as defined in Note 1), all outstanding general partner units converted into a non-economic general partner interest in WES Operating and WES Operating common units and all outstanding Class C units converted into WES Operating common units on a one-for-one basis.

Consolidated Balance Sheets -_2

Consolidated Balance Sheets - WES Operating (Parenthetical) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Common units issued		452,990,862	218,937,797
Common units outstanding		452,990,862	218,937,797
Accounts receivable, net	[1]	$ 212,423	$ 221,164	[2]
Other current assets	[3]	23,472	27,056	[2]
Other assets	[4]	74,694	67,194	[2]
Accrued liabilities	[5]	141,442	129,148	[2]
Other liabilities	[6]	151,118	132,130	[2]
Affiliates [Member]
Accounts receivable, net		68,500	72,600
Other current assets		7,400	3,700
Other assets		42,900	42,200
Accrued liabilities		3,500	2,200
Other liabilities		$ 60,600	$ 47,800
WES Operating [Member]
General partner units issued		0	2,583,068
General partner units outstanding		0	2,583,068
Accounts receivable, net	[7]	$ 214,148	$ 221,373	[2]
Other current assets	[8]	23,434	26,181	[2]
Other assets	[9]	74,694	67,194	[2]
Accrued liabilities	[10]	141,267	127,874	[2]
Other liabilities	[11]	$ 151,118	$ 132,130	[2]
WES Operating [Member] | Common Units [Member]
Common units issued		318,675,578	152,609,285
Common units outstanding		318,675,578	152,609,285
WES Operating [Member] | Class C Units [Member]
Common units issued		0	14,372,665
Common units outstanding		0	14,372,665
WES Operating [Member] | Affiliates [Member]
Accounts receivable, net		$ 70,200	$ 72,800
Other current assets		7,400	3,700
Other assets		42,900	42,200
Accrued liabilities		3,500	2,200
Other liabilities		$ 60,600	$ 47,800
[1]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $68.5 million and $72.6 million as of March 31, 2019, and December 31, 2018, respectively.
[2]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[3]	Other current assets includes affiliate amounts of $7.4 million and $3.7 million as of March 31, 2019, and December 31, 2018, respectively.
[4]	Other assets includes affiliate amounts of $42.9 million and $42.2 million as of March 31, 2019, and December 31, 2018, respectively.
[5]	Accrued liabilities includes affiliate amounts of $3.5 million and $2.2 million as of March 31, 2019, and December 31, 2018, respectively.
[6]	Other liabilities includes affiliate amounts of $60.6 million and $47.8 million as of March 31, 2019, and December 31, 2018, respectively.
[7]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $70.2 million and $72.8 million as of March 31, 2019, and December 31, 2018, respectively.
[8]	Other current assets includes affiliate amounts of $7.4 million and $3.7 million as of March 31, 2019, and December 31, 2018, respectively.
[9]	Other assets includes affiliate amounts of $42.9 million and $42.2 million as of March 31, 2019, and December 31, 2018, respectively.
[10]	Accrued liabilities includes affiliate amounts of $3.5 million and $2.2 million as of March 31, 2019, and December 31, 2018, respectively.
[11]	Other liabilities includes affiliate amounts of $60.6 million and $47.8 million as of March 31, 2019, and December 31, 2018, respectively.

Consolidated Statements of Eq_3

Consolidated Statements of Equity and Partners' Capital - WES Operating - USD ($) $ in Thousands		Total		Chipeta [Member]	Net Investment by Anadarko [Member]		Common Units [Member]		Noncontrolling Interest [Member]		Noncontrolling Interest [Member]Chipeta [Member]	WES Operating [Member]		WES Operating [Member]Chipeta [Member]	WES Operating [Member]Net Investment by Anadarko [Member]		WES Operating [Member]Common Units [Member]		WES Operating [Member]Class C Units [Member]		WES Operating [Member]General Partner [Member]		WES Operating [Member]Noncontrolling Interest [Member]	WES Operating [Member]Noncontrolling Interest [Member]Chipeta [Member]
Balance at Dec. 31, 2017	[1]	$ 4,995,050			$ 1,050,171		$ 1,061,125		$ 2,883,754			$ 5,021,182			$ 1,050,171		$ 2,950,010		$ 780,040		$ 179,232		$ 61,729
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income (loss)	[1]	181,010			30,522		101,005		49,483			182,870			30,522		59,133		6,791		83,439		2,985
Above-market component of swap agreements with Anadarko	[1]	14,282	[2]				14,282	[2]				14,282	[3]				14,282	[3]
Amortization of beneficial conversion feature of Class C units	[1]											0					(810)		810
Distributions to noncontrolling interest owners	[1]			$ (3,353)							$ (3,353)			$ (3,353)										$ (3,353)
Distributions to WES Operating unitholders	[1]	(120,140)					(120,140)					(216,586)					(140,394)				(76,192)
Contributions of equity-based compensation from Anadarko	[1]	1,470					1,470					1,464					1,435				29
Net pre-acquisition contributions from (distributions to) Anadarko	[1]	64,251			64,251							64,251			64,251
Adjustments of net deferred tax liabilities	[1]	(175)			(175)							(175)			(175)
Other	[1]	150					58		92			91					91
Balance at Mar. 31, 2018	[1]	4,994,493			1,145,398		1,041,066		2,808,029			5,020,246			1,145,398		2,842,612		784,105		185,812		62,319
Increase (Decrease) in Partners' Capital [Roll Forward]
Cumulative effect of accounting change	[1]	(43,780)			629		(14,209)		(30,200)			(43,780)			629		(41,135)		(3,536)		(696)		958
Balance at Dec. 31, 2018	[1]	4,892,683			1,388,018		951,888		2,552,777			4,919,597			1,388,018		2,475,540		791,410		206,862		57,767
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income (loss)		211,979			29,116		89,544		93,319			214,450			29,116		170,847		10,636		1,997		1,854
Cumulative impact of the Merger transactions		0	[4]				3,169,800	[4]	(3,169,800)	[4]		0	[5]				926,236	[5]	(802,588)	[5]	(123,648)	[5]
Above-market component of swap agreements with Anadarko		7,407	[6]				7,407	[6]				7,407	[7]				7,407	[7]
Amortization of beneficial conversion feature of Class C units												0					(542)		542
Distributions to noncontrolling interest owners				$ (1,935)							$ (1,935)			$ (1,935)										$ (1,935)
Distributions to WES Operating unitholders		(131,910)					(131,910)					(263,358)					(178,128)				(85,230)
Acquisitions from affiliates		(2,007,501)	[8]		(2,141,827)	[8]	106,856	[8]	27,470	[8]		(2,007,501)	[9]		(2,141,827)	[9]	134,326	[9]
Contributions of equity-based compensation from Anadarko		1,840					1,840					1,838					1,819				19
Net pre-acquisition contributions from (distributions to) Anadarko		451,591			451,591							451,591			451,591
Adjustments of net deferred tax liabilities		268,727			273,102		(4,375)					268,727			273,102		(4,375)
Other		(341)					(332)		(9)			268					268
Balance at Mar. 31, 2019		$ 3,591,541			$ 0		$ 3,437,922		$ 153,619			$ 3,591,084			$ 0		$ 3,533,398		$ 0		$ 0		$ 57,686
[1]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[2]	See Note 6.
[3]	See Note 6.
[4]	See Note 1.
[5]	See Note 1.
[6]	See Note 6.
[7]	See Note 6.
[8]	The amounts allocated to common unitholders and noncontrolling interests represent a noncash investing activity related to the assets and liabilities assumed in the AMA acquisition.
[9]	The amount allocated to common unitholders represents a noncash investing activity related to the assets and liabilities assumed in the AMA acquisition.

Consolidated Statements of Ca_3

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).

Consolidated Statements of Ca_4

Consolidated Statements of Cash Flows - WES Operating (Parenthetical) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Borrowings, net of debt issuance costs	[1]	$ 2,430,750	$ 1,444,082	[2]
Repayments of debt	[3]	467,595	630,000	[2]
WES Operating [Member]
Borrowings, net of debt issuance costs	[4]	2,430,750	1,444,090	[2]
Repayments of debt	[5]	439,595	630,000	[2]
Affiliates [Member]
Borrowings, net of debt issuance costs		11,000	106,600
Repayments of debt		439,600
Affiliates [Member] | WES Operating [Member]
Borrowings, net of debt issuance costs		11,000	$ 106,600
Repayments of debt		$ 439,600
[1]	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.
[2]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[3]	For the three months ended March 31, 2019, includes a $439.6 million repayment to settle the APCWH Note Payable. See Note 6.
[4]	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.
[5]	For the three months ended March 31, 2019, includes a $439.6 million repayment to settle the APCWH Note Payable. See Note 6.

Description of Business and Bas

Description of Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Description of Business and Basis of Presentation	1. DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION General. Western Midstream Partners, LP (formerly Western Gas Equity Partners, LP) is a Delaware master limited partnership formed in September 2012. Western Midstream Operating, LP (formerly Western Gas Partners, LP, and together with its subsidiaries, “WES Operating”) is a Delaware limited partnership formed by Anadarko Petroleum Corporation in 2007 to acquire, own, develop and operate midstream assets. Western Midstream Partners, LP owns, directly and indirectly, a 98.0% limited partner interest in WES Operating, and directly owns all of the outstanding equity interests of Western Midstream Operating GP, LLC, which holds the entire non-economic general partner interest in WES Operating. For purposes of these consolidated financial statements, the “Partnership” refers to Western Midstream Partners, LP in its individual capacity or to Western Midstream Partners, LP and its subsidiaries, including Western Midstream Operating GP, LLC and WES Operating, as the context requires. “WES Operating GP” refers to Western Midstream Operating GP, LLC, individually as the general partner of WES Operating, and excludes WES Operating. The Partnership’s general partner, Western Midstream Holdings, LLC (the “general partner”), is a wholly owned subsidiary of Anadarko Petroleum Corporation. “Anadarko” refers to Anadarko Petroleum Corporation and its subsidiaries, excluding the Partnership and the general partner, and “affiliates” refers to subsidiaries of Anadarko, excluding the Partnership, but including equity interests in Fort Union Gas Gathering, LLC (“Fort Union”), White Cliffs Pipeline, LLC (“White Cliffs”), Rendezvous Gas Services, LLC (“Rendezvous”), Enterprise EF78 LLC (the “Mont Belvieu JV”), Texas Express Pipeline LLC (“TEP”), Texas Express Gathering LLC (“TEG”), Front Range Pipeline LLC (“FRP”), Whitethorn Pipeline Company LLC (“Whitethorn LLC”), Cactus II Pipeline LLC (“Cactus II”), Saddlehorn Pipeline Company, LLC (“Saddlehorn”), Panola Pipeline Company, LLC (“Panola”), Mi Vida JV LLC (“Mi Vida”), Ranch Westex JV LLC (“Ranch Westex”) and Red Bluff Express Pipeline, LLC (“Red Bluff Express”). See Note 3 . The interests in TEP, TEG and FRP are referred to collectively as the “TEFR Interests.” “MGR assets” refers to the Red Desert complex and the Granger straddle plant. The “West Texas complex” refers to the Delaware Basin Midstream, LLC (“DBM”) complex and DBJV and Haley systems. The Partnership is engaged in the business of gathering, compressing, treating, processing and transporting natural gas; gathering, stabilizing and transporting condensate, natural gas liquids (“NGLs”) and crude oil; and gathering and disposing of produced water. In addition, in its capacity as a processor of natural gas, the Partnership also buys and sells natural gas, NGLs and condensate on behalf of itself and as agent for its customers under certain of its contracts. The Partnership provides these midstream services for Anadarko, as well as for third-party customers. As of March 31, 2019 , the Partnership’s assets and investments consisted of the following: Owned and Operated Operated Interests Non-Operated Interests Equity Interests Gathering systems (1) 17 2 3 2 Treating facilities 35 3 — 3 Natural gas processing plants/trains 24 3 — 5 NGLs pipelines 2 — — 4 Natural gas pipelines 5 — — 1 Oil pipelines 3 1 — 3 (1) Includes the DBM water systems. These assets and investments are located in the Rocky Mountains (Colorado, Utah and Wyoming), North-central Pennsylvania, Texas and New Mexico. Mentone Train II, a processing train and part of the West Texas complex, commenced operation at the end of the first quarter of 2019. 1. DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (CONTINUED) Merger transactions . On February 28, 2019, the Partnership, WES Operating, Anadarko and certain of their affiliates consummated the transactions contemplated by the Contribution Agreement and Agreement and Plan of Merger (the “Merger Agreement”), dated as of November 7, 2018, pursuant to which, among other things, Clarity Merger Sub, LLC, a wholly owned subsidiary of the Partnership, merged with and into WES Operating, with WES Operating continuing as the surviving entity and a subsidiary of the Partnership (the “Merger”). In connection with the closing of the Merger, (i) the common units of WES Operating, which previously traded under the symbol “WES,” ceased to trade on the New York Stock Exchange (“NYSE”), (ii) the common units of the Partnership, which previously traded under the symbol “WGP,” began to trade on the NYSE under the symbol “WES,” (iii) the Partnership changed its name from Western Gas Equity Partners, LP to Western Midstream Partners, LP and (iv) WES Operating changed its name from Western Gas Partners, LP to Western Midstream Operating, LP. The Merger Agreement also provided that the Partnership, WES Operating and Anadarko cause their respective affiliates to cause the following transactions, among others, to occur immediately prior to the Merger becoming effective in the order as follows: (1) Anadarko E&P Onshore LLC and WGR Asset Holding Company LLC (“WGRAH”) (the “Contributing Parties”) contributed to WES Operating all of their interests in each of Anadarko Wattenberg Oil Complex LLC, Anadarko DJ Oil Pipeline LLC, Anadarko DJ Gas Processing LLC, Wamsutter Pipeline LLC, DBM Oil Services, LLC, Anadarko Pecos Midstream LLC, Anadarko Mi Vida LLC and APC Water Holdings 1, LLC (“APCWH”) to WGR Operating, LP, Kerr-McGee Gathering LLC and DBM (each wholly owned by WES Operating) in exchange for aggregate consideration of $1.814 billion in cash from WES Operating, minus the outstanding amount payable pursuant to an intercompany note (the “APCWH Note Payable”) assumed by WES Operating in connection with the transaction, and 45,760,201 WES Operating common units; (2) APC Midstream Holdings, LLC (“AMH”) sold to WES Operating its interests in Saddlehorn and Panola in exchange for aggregate consideration of $193.9 million in cash; (3) WES Operating contributed cash in an amount equal to the outstanding balance of the APCWH Note Payable immediately prior to the effective time of the Merger to APCWH, and APCWH paid such cash to Anadarko in satisfaction of the APCWH Note Payable; (4) the Class C units converted into WES Operating common units on a one -for-one basis; and (5) WES Operating and WES Operating GP caused the conversion of the incentive distribution rights (“IDRs”) and the 2,583,068 general partner units in WES Operating held by WES Operating GP into a non-economic general partner interest in WES Operating and 105,624,704 WES Operating common units. The 45,760,201 WES Operating common units issued to the Contributing Parties, less 6,375,284 WES Operating common units retained by WGRAH, converted into the right to receive an aggregate of 55,360,984 common units of the Partnership upon the consummation of the Merger. Each WES Operating common unit issued and outstanding immediately prior to the closing of the Merger (other than WES Operating common units owned by the Partnership and WES Operating GP, and certain common units held by subsidiaries of Anadarko) was converted into the right to receive 1.525 common units of the Partnership. See Note 10 for additional information. Chevron merger. On April 11, 2019, Anadarko, the indirect general partner and majority unitholder of the Partnership, which is the indirect general partner and majority unitholder of WES Operating, entered into the Chevron Merger Agreement pursuant to which, and subject to the conditions of the agreement, all outstanding shares of Anadarko will be acquired by Chevron in a stock and cash transaction. Anadarko expects the acquisition to close in the second half of 2019, although it is subject to Anadarko stockholder approval, regulatory approvals and other customary closing conditions. 1. DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (CONTINUED) Basis of presentation. The following table outlines the ownership interests and the accounting method of consolidation used in the consolidated financial statements for entities not wholly owned: Percentage Interest Equity investments (1) Fort Union 14.81 % White Cliffs 10.00 % Rendezvous 22.00 % Mont Belvieu JV 25.00 % TEP 20.00 % TEG 20.00 % FRP 33.33 % Whitethorn LLC 20.00 % Cactus II 15.00 % Saddlehorn 20.00 % Panola 15.00 % Mi Vida 50.00 % Ranch Westex 50.00 % Red Bluff Express 30.00 % Proportionate consolidation (2) Marcellus Interest systems 33.75 % Springfield system 50.10 % Full consolidation Chipeta (3) 75.00 % (1) Investments in non-controlled entities over which the Partnership exercises significant influence are accounted for under the equity method. “Equity investment throughput” refers to the Partnership’s share of average throughput for these investments. (2) The Partnership proportionately consolidates its associated share of the assets, liabilities, revenues and expenses attributable to these assets. (3) The 25% interest in Chipeta Processing LLC (“Chipeta”) held by a third-party member is reflected within noncontrolling interests in the consolidated financial statements, in addition to the noncontrolling interests noted below. The consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”). The consolidated financial statements include the accounts of the Partnership and entities in which it holds a controlling financial interest, including WES Operating and WES Operating GP. All significant intercompany transactions have been eliminated. Certain information and note disclosures commonly included in annual financial statements have been condensed or omitted pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). Accordingly, the accompanying consolidated financial statements and notes should be read in conjunction with the Partnership and WES Operating’s 2018 Forms 10-K, as filed with the SEC on February 20, 2019 . 1. DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (CONTINUED) The consolidated financial results of WES Operating are included in the Partnership’s consolidated financial statements. Throughout these notes to consolidated financial statements, and to the extent material, any differences between the consolidated financial results of the Partnership and WES Operating are discussed separately. The Partnership’s consolidated financial statements differ from those of WES Operating primarily as a result of (i) the presentation of noncontrolling interest ownership (see Noncontrolling interests below and Note 5 ), (ii) the elimination of WES Operating GP’s investment in WES Operating with WES Operating GP’s underlying capital account, (iii) the general and administrative expenses incurred by the Partnership, which are separate from, and in addition to, those incurred by WES Operating, (iv) the inclusion of the impact of Partnership equity balances and Partnership distributions, and (v) the senior secured revolving credit facility (“WGP RCF”) until its repayment in March 2019. See Note 10 . Adjustments to previously issued financial statements. The consolidated statements of operations for the three months ended March 31, 2018, include adjustments to revenue and cost of product expense of the following amounts: (i) $14.3 million increase in Service revenues - fee based, (ii) $5.3 million increase in Product sales and (iii) $19.6 million increase in Cost of product. During the third quarter of 2018, management determined that under Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) adopted on January 1, 2018, the Partnership’s marketing affiliate was acting as its agent in certain product sales transactions on behalf of the Partnership and in performing marketing services on behalf of the Partnership’s customers. The adjustments have no impact to Operating income (loss), Net income (loss), the balance sheets, cash flows or any non-GAAP metric the Partnership uses to evaluate its operations (see Key Performance Metrics under Part I, Item 2 of this Form 10-Q) and are not considered material to the results of operations for the three months ended March 31, 2018. Presentation of Partnership assets. The term “Partnership assets” includes both the assets owned and the interests accounted for under the equity method by the Partnership, through its partnership interests in WES Operating as of March 31, 2019 (see Note 8 ). Because the Partnership owns the entire non-economic general partner interest in and controls WES Operating GP, and the general partner is controlled by Anadarko, each of the Partnership’s acquisitions of assets from Anadarko has been considered a transfer of net assets between entities under common control. As such, assets acquired from Anadarko were initially recorded at Anadarko’s historic carrying value, which did not correlate to the total acquisition price paid by the Partnership. Further, after an acquisition of assets from Anadarko, the Partnership is required to recast its financial statements to include the activities of such assets from the date of common control. For those periods requiring recast, the consolidated financial statements for periods prior to the acquisition of assets from Anadarko are prepared from Anadarko’s historical cost-basis accounts and may not necessarily be indicative of the actual results of operations that would have occurred if the Partnership had owned the assets during the periods reported. Net income (loss) attributable to the assets acquired from Anadarko for periods prior to the Partnership’s acquisition of such assets is not allocated to the limited partners. Use of estimates. In preparing financial statements in accordance with GAAP, management makes informed judgments and estimates that affect the reported amounts of assets, liabilities, revenues and expenses. Management evaluates its estimates and related assumptions regularly, using historical experience and other methods considered reasonable. Changes in facts and circumstances or additional information may result in revised estimates and actual results may differ from these estimates. Effects on the business, financial condition and results of operations resulting from revisions to estimates are recognized when the facts that give rise to the revisions become known. The information included herein reflects all normal recurring adjustments which are, in the opinion of management, necessary for a fair presentation of the consolidated financial statements, and certain prior-period amounts have been reclassified to conform to the current-year presentation. 1. DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (CONTINUED) Noncontrolling interests. For periods subsequent to the consummation of the Merger, the Partnership’s noncontrolling interests in the consolidated financial statements consisted of (i) the 25% interest in Chipeta held by a third-party member and (ii) the 2.0% limited partner interest in WES Operating held by a subsidiary of Anadarko. For periods prior to the consummation of the Merger, the Partnership’s noncontrolling interests in the consolidated financial statements consisted of (i) the 25% interest in Chipeta held by a third-party member, (ii) the publicly held limited partner interests in WES Operating, (iii) the common units issued by WES Operating to subsidiaries of Anadarko as part of the consideration paid for prior acquisitions from Anadarko, and (iv) the Class C units issued by WES Operating to a subsidiary of Anadarko as part of the funding for the acquisition of DBM. For all periods presented, WES Operating’s noncontrolling interest in the consolidated financial statements consisted of the 25% interest in Chipeta held by a third-party member. See Note 5 . When WES Operating issues equity, the carrying amount of the noncontrolling interest reported by the Partnership is adjusted to reflect the noncontrolling ownership interest in WES Operating. The resulting impact of such noncontrolling interest adjustment on the Partnership’s interest in WES Operating is reflected as an adjustment to the Partnership’s partners’ capital. Shutdown of gathering systems. In May 2018, after assessing a number of factors, with safety and protection of the environment as the primary focus, the Partnership decided to take the Kitty Draw gathering system in Wyoming (part of the Hilight system) and the Third Creek gathering system in Colorado (part of the DJ Basin complex) permanently out of service. During the second quarter of 2018, an accrual of $10.9 million in anticipated costs associated with the shutdown of the systems was recorded as a reduction in affiliate Product sales in the consolidated statements of operations. During the first quarter of 2019, $5.5 million of the accrual related to the Kitty Draw gathering system was reversed due to producer settlements being less than initial estimates. Segments. The Partnership’s operations continue to be organized into a single operating segment, the assets of which gather, compress, treat, process and transport natural gas; gather, stabilize and transport condensate, NGLs and crude oil; and gather and dispose of produced water in the United States. Recently adopted accounting standards. ASU 2016-02, Leases (Topic 842) requires lessees to recognize a lease liability and a right-of-use (“ROU”) asset for all leases, including operating leases, with a term greater than 12 months on the balance sheet. This ASU modifies the definition of a lease and outlines the recognition, measurement, presentation, and disclosure of leasing arrangements by both lessees and lessors. The Partnership adopted this standard on January 1, 2019, using the modified retrospective method applied to all leases that existed on January 1, 2019, and prior-period financial statements were not adjusted. The Partnership elected not to reassess contracts that commenced prior to adoption, to continue applying its current accounting policy for existing or expired land easements and not to recognize ROU assets or lease liabilities for short-term leases. Leases. The Partnership determines if an arrangement is a lease based on rights and obligations conveyed at inception of a contract. Operating leases are included in other assets, accrued liabilities and other liabilities on the consolidated balance sheets. ROU assets and lease liabilities are recognized at the commencement date based on the present value of future lease payments over the lease term. As the rate implicit in the Partnership’s leases is generally not readily determinable, the Partnership discounts lease liabilities using the Partnership’s incremental borrowing rate at the commencement date. Non-lease components associated with leases that begin in 2019 or later are accounted for as part of the lease component, and prepaid lease payments are included in ROU assets. Options to extend or terminate a lease are included in the lease term when it is reasonably certain that the Partnership will exercise that option. Leases of 12 months or less are not recognized on the consolidated balance sheets. Lease cost is recognized over the lease term and is generally recognized on a straight-line basis. Variable lease payments are recognized when the obligation for those payments is incurred.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	2. REVENUE FROM CONTRACTS WITH CUSTOMERS The following table summarizes revenue from contracts with customers: Three Months Ended thousands 2019 2018 Revenue from customers Service revenues – fee based $ 579,974 $ 393,773 Service revenues – product based 19,379 23,423 Product sales 72,800 84,868 Total revenue from customers 672,153 502,064 Revenue from other than customers Net gains (losses) on commodity price swap agreements (667 ) (1,243 ) Other 397 233 Total revenues and other $ 671,883 $ 501,054 Contract balances. Receivables from customers, which are included in Accounts receivable, net on the consolidated balance sheets were $315.3 million and $214.3 million as of March 31, 2019 , and December 31, 2018 , respectively. Contract assets primarily relate to accrued deficiency fees the Partnership expects to charge customers once the related performance periods are completed. The following table summarizes the current period activity related to contract assets from contracts with customers: thousands Balance at December 31, 2018 $ 47,621 Amounts transferred to Accounts receivable, net that were included in the contract assets balance at the beginning of the period (1,376 ) Additional estimated revenues recognized 3,810 Balance at March 31, 2019 $ 50,055 Contract assets at March 31, 2019 Other current assets $ 7,172 Other assets 42,883 Total contract assets from contracts with customers $ 50,055 2. REVENUE FROM CONTRACTS WITH CUSTOMERS (CONTINUED) Contract liabilities primarily relate to (i) fees that are charged to customers for only a portion of the contract term and must be recognized as revenues over the expected period of customer benefit, (ii) fixed and variable fees under cost of service contracts that are received from customers for which revenue recognition is deferred and (iii) aid in construction payments received from customers that must be recognized over the expected period of customer benefit. The following table summarizes the current period activity related to contract liabilities from contracts with customers: thousands Balance at December 31, 2018 $ 145,624 Cash received or receivable, excluding revenues recognized during the period 15,213 Revenues recognized that were included in the contract liability balance at the beginning of the period (9,279 ) Balance at March 31, 2019 $ 151,558 Contract liabilities at March 31, 2019 Accrued liabilities $ 6,364 Other liabilities 145,194 Total contract liabilities from contracts with customers $ 151,558 Transaction price allocated to remaining performance obligations. Revenues expected to be recognized from certain performance obligations that are unsatisfied (or partially unsatisfied) as of March 31, 2019 , are reflected in the following table. The Partnership applies the optional exemptions in Topic 606 and does not disclose consideration for remaining performance obligations with an original expected duration of one year or less or for variable consideration related to unsatisfied (or partially unsatisfied) performance obligations. Therefore, the following table represents only a portion of expected future revenues from existing contracts as most future revenues from customers are dependent on future variable customer volumes and, in some cases, variable commodity prices for those volumes. thousands Remainder of 2019 $ 532,477 2020 862,428 2021 911,450 2022 976,136 2023 932,921 Thereafter 4,500,175 Total $ 8,715,587

Acquisitions and Divestitures

Acquisitions and Divestitures	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Acquisitions and Divestitures	3. ACQUISITIONS AND DIVESTITURES AMA acquisition. In February 2019, WES Operating acquired the following assets from Anadarko (see Note 1 ), which are collectively referred to as the Anadarko Midstream Assets (“AMA”): • Wattenberg processing plant. The Wattenberg processing plant consists of a cryogenic train (with capacity of 190 million cubic feet per day (“MMcf/d”)) and a refrigeration train (with capacity of 100 MMcf/d) located in Adams County, Colorado, now part of the DJ Basin complex. • Wamsutter pipeline. The Wamsutter pipeline is a crude oil gathering pipeline located in Sweetwater County, Wyoming and delivers crude oil into Andeavor’s Wamsutter Pipeline System. • DJ Basin oil system. The DJ Basin oil system consists of (i) a crude oil gathering system, (ii) a centralized oil stabilization facility (“COSF”) and (iii) a 12 -mile crude oil pipeline, located in Weld County, Colorado. The COSF consists of Trains I through VI with total capacity of 155 thousand barrels per day (“MBbls/d”) and two storage tanks with total capacity of 500,000 barrels. Train VI commenced operation in 2018. The pipeline connects the COSF to Tampa Rail. • DBM oil system. The DBM oil system consists of (i) a crude oil gathering system, (ii) three central production facilities (“CPFs”), which include ten processing trains with total capacity of 71 MBbls/d, (iii) three storage tanks with total capacity of 30,000 barrels, (iv) a 14 -mile crude oil pipeline, and (v) two regional oil treating facilities (“ROTFs”), which include four trains with total capacity of 120 MBbls/d, located in Reeves and Loving Counties, Texas. The ROTFs commenced operation in 2018. The pipeline transports crude oil from the DBM oil system and one third-party CPF into Plains All American Pipeline. • APC water systems. The APC water systems consist of five produced-water disposal systems with total capacity of 565 MBbls/d, located in Reeves, Loving, Winkler and Ward Counties, Texas, which are now part of the DBM water systems. One produced-water disposal system commenced operation in 2017 and the others commenced operation in 2018. • A 20% interest in Saddlehorn. Saddlehorn owns (i) a crude oil and condensate pipeline (excluding pipeline capacity leased by Saddlehorn) that originates in Laramie County, Wyoming and terminates in Cushing, Oklahoma, and (ii) four storage tanks with total capacity of 300,000 barrels. The Saddlehorn interest is accounted for under the equity method and the pipeline is operated by a third party. • A 15% interest in Panola. Panola owns a 248 -mile NGLs pipeline that originates in Panola County, Texas and terminates in Mont Belvieu, Texas. The Panola interest is accounted for under the equity method and the pipeline is operated by a third party. • A 50% interest in Mi Vida. Mi Vida owns a cryogenic gas processing plant (with capacity of 200 MMcf/d) located in Ward County, Texas. The interest in Mi Vida is accounted for under the equity method and the processing plant is operated by a third party. • A 50% interest in Ranch Westex. Ranch Westex owns a processing plant consisting of a cryogenic train (with capacity of 100 MMcf/d) and a refrigeration train (with capacity of 25 MMcf/d), located in Ward County, Texas. The interest in Ranch Westex is accounted for under the equity method and the processing plant is operated by a third party. 3. ACQUISITIONS AND DIVESTITURES (CONTINUED) Because the acquisition of AMA was a transfer of net assets between entities under common control, the Partnership and WES Operating’s historical financial statements previously filed with the SEC have been recast in this Form 10-Q to include the results attributable to AMA as if it was owned for all periods presented. The consolidated financial statements for periods prior to the acquisition of AMA have been prepared from Anadarko’s historical cost-basis accounts and may not necessarily be indicative of the actual results of operations that would have occurred if AMA had been owned during the periods reported. The following tables present the impact of AMA on Revenues and other, Equity income, net – affiliates and Net income (loss) as presented in the Partnership and WES Operating’s historical consolidated statements of operations: Three Months Ended March 31, 2018 thousands Partnership Historical (1) AMA Eliminations Combined Revenues and other $ 456,802 $ 51,664 $ (7,412 ) $ 501,054 Equity income, net – affiliates 20,424 9,805 — 30,229 Net income (loss) 150,488 30,522 — 181,010 Three Months Ended March 31, 2018 thousands WES Operating Historical (1) AMA Eliminations Combined Revenues and other $ 456,802 $ 51,664 $ (7,412 ) $ 501,054 Equity income, net – affiliates 20,424 9,805 — 30,229 Net income (loss) 152,348 30,522 — 182,870 (1) See Adjustments to previously issued financial statements within Note 1 . Red Bluff Express acquisition. In January 2019, the Partnership acquired a 30% interest in Red Bluff Express, which owns a natural gas pipeline operated by a third party connecting processing plants in Reeves and Loving Counties, Texas to the WAHA hub in Pecos County, Texas. The Partnership acquired its 30% interest from a third party via an initial net investment of $92.5 million , which represented its share of costs incurred up to the date of acquisition. The initial investment was funded with cash on hand and the interest in Red Bluff Express is accounted for under the equity method. See Note 8 .

Partnership Distributions

Partnership Distributions	3 Months Ended
	Mar. 31, 2019
Distributions Made to Members or Limited Partners [Abstract]
Partnership Distributions	4. PARTNERSHIP DISTRIBUTIONS The partnership agreement requires the Partnership to distribute all of its available cash (as defined in its partnership agreement) to unitholders of record on the applicable record date within 55 days of the end of each quarter. The Board of Directors of the general partner (the “Board of Directors”) declared the following cash distributions to the Partnership’s unitholders for the periods presented: thousands except per-unit amounts Quarters Ended Total Quarterly Total Quarterly Date of 2018 (1) March 31 $ 0.56875 $ 124,518 May 2018 June 30 0.58250 127,531 August 2018 September 30 0.59500 130,268 November 2018 December 31 0.60250 131,910 February 2019 2019 March 31 (2) $ 0.61000 $ 276,324 May 2019 (1) The 2018 distributions were declared and paid prior to the closing of the Merger. (2) The Board of Directors declared a cash distribution to the Partnership’s unitholders for the first quarter of 2019 of $0.61000 per unit, or $276.3 million in aggregate. The cash distribution is payable on May 14, 2019 , to unitholders of record at the close of business on May 1, 2019 . Available cash. The amount of available cash (as defined in the partnership agreement) generally is all cash on hand at the end of the quarter, plus, at the discretion of the general partner, working capital borrowings made subsequent to the end of such quarter, less the amount of cash reserves established by the general partner to provide for the proper conduct of the Partnership’s business, including reserves to fund future capital expenditures; to comply with applicable laws, debt instruments or other agreements; or to provide funds for distributions to its unitholders for any one or more of the next four quarters. Working capital borrowings generally include borrowings made under a credit facility or similar financing arrangement. Working capital borrowings may only be those that, at the time of such borrowings, were intended to be repaid within 12 months. In all cases, working capital borrowings are used solely for working capital purposes or to fund distributions to partners. WES Operating partnership distributions. For the 2018 periods noted below, WES Operating paid the following cash distributions to WES Operating’s common and general partner unitholders: thousands except per-unit amounts Quarters Ended Total Quarterly Total Quarterly Date of 2018 March 31 $ 0.935 $ 221,133 May 2018 June 30 0.950 225,691 August 2018 September 30 0.965 230,239 November 2018 December 31 0.980 234,787 February 2019 Immediately prior to the closing of the Merger, the IDRs and the general partner units were converted into a non-economic general partner interest in WES Operating and WES Operating common units, and upon consummation of the Merger, all WES Operating common units held by the public and subsidiaries of Anadarko (other than common units held by the Partnership, WES Operating GP and 6.4 million common units held by a subsidiary of Anadarko) were converted into common units of the Partnership. Beginning in the first quarter of 2019, WES Operating will make distributions to the Partnership and a subsidiary of Anadarko in respect of their proportionate share of limited partner interests in WES Operating. For the three months ended March 31, 2019, WES Operating will distribute $283.3 million to its limited partners. See Note 5 . 4. PARTNERSHIP DISTRIBUTIONS (CONTINUED) WES Operating Class C unit distributions. Prior to the closing of the Merger, WES Operating’s Class C units received quarterly distributions at a rate equivalent to WES Operating’s publicly-traded common units. The distributions were paid in the form of additional Class C Units (“PIK Class C units”) and were disregarded with respect to WES Operating’s distributions of WES Operating’s available cash. The number of PIK Class C units issued in connection with a distribution payable on the Class C units was determined by dividing the corresponding distribution attributable to the Class C units by the volume-weighted-average price of WES Operating’s common units for the ten days immediately preceding the payment date for the common unit distribution, less a 6% discount. WES Operating recorded the PIK Class C unit distributions at fair value at the time of issuance. This Level 2 fair value measurement used WES Operating’s unit price as a significant input in the determination of the fair value. See Note 5 for further discussion of the Class C units. In February 2019, immediately prior to the closing of the Merger, all outstanding Class C units converted into WES Operating common units on a one -for-one basis (see Note 1 ). WES Operating’s general partner interest and incentive distribution rights. Prior to the closing of the Merger, WES Operating GP was entitled to 1.5% of all quarterly distributions that WES Operating made prior to its liquidation and, as the former holder of the IDRs, was entitled to incentive distributions at the maximum distribution sharing percentage of 48.0% for all prior periods presented. Immediately prior to the closing of the Merger, the IDRs and the general partner units converted into a non-economic general partner interest in WES Operating and WES Operating common units (see Note 1 ).

Equity and Partners' Capital

Equity and Partners' Capital	3 Months Ended
	Mar. 31, 2019
Partners' Capital Notes [Abstract]
Equity and Partners' Capital	5. EQUITY AND PARTNERS’ CAPITAL Holdings of Partnership equity. The Partnership’s common units are listed on the NYSE under the symbol “WES.” As of March 31, 2019 , Anadarko held 251,197,617 common units, representing a 55.5% limited partner interest in the Partnership, and, through its ownership of the general partner, Anadarko indirectly held the entire non-economic general partner interest in the Partnership. The public held 201,793,245 common units, representing a 44.5% limited partner interest in the Partnership. In February 2019, the Partnership issued common units in connection with the closing of the Merger (see Note 1 ) as follows: Partnership common units outstanding prior to the Merger 218,937,797 WES Operating common units outstanding prior to the Merger 152,609,285 WES Operating Class C units outstanding prior to the Merger 14,681,388 Less: WES Operating common units owned by the Partnership (50,132,046 ) WES Operating common units subject to conversion into Partnership common units 117,158,627 Exchange ratio per unit 1.525 Partnership common units issued for WES Operating common units (1) 178,692,081 WES Operating common units issued as part of the AMA acquisition 45,760,201 Less: WES Operating common units retained by a subsidiary of Anadarko (6,375,284 ) WES Operating acquisition common units subject to conversion into Partnership common units 39,384,917 Conversion ratio per unit 1.4056 Partnership common units issued for WES Operating acquisition common units 55,360,984 Partnership common units outstanding at March 31, 2019 452,990,862 (1) Total Partnership units issued upon consummation of the Merger exceeds the calculation of such units using the exchange ratio due to the rounding convention reflected in the Merger Agreement. 5. EQUITY AND PARTNERS’ CAPITAL (CONTINUED) Holdings of WES Operating equity. As of March 31, 2019 , (i) the Partnership, directly and indirectly through its ownership of WES Operating GP, owned a 98.0% limited partner interest and the entire non-economic general partner interest in WES Operating and (ii) Anadarko, through its ownership of WGRAH, owned a 2.0% limited partner interest in WES Operating, which is reflected as a noncontrolling interest within the consolidated financial statements of the Partnership (see Note 1 ). WES Operating interests. The following table summarizes WES Operating’s units issued during the three months ended March 31, 2019 : Common Units Class C Units General Partner Units Total Balance at December 31, 2018 152,609,285 14,372,665 2,583,068 169,565,018 PIK Class C units — 308,723 — 308,723 Conversion of Class C units (1) 14,681,388 (14,681,388 ) — — IDR and General partner unit conversion (1) 105,624,704 — (2,583,068 ) 103,041,636 Units issued as part of the AMA acquisition (1) 45,760,201 — — 45,760,201 Balance at March 31, 2019 318,675,578 — — 318,675,578 (1) See Note 1 for further details on the units issued and converted in connection with the closing of the Merger. WES Operating Class C units. In November 2014, WES Operating issued 10,913,853 Class C units to AMH, pursuant to a Unit Purchase Agreement with Anadarko and AMH. The Class C units were issued to partially fund the acquisition of DBM. The Class C units were issued at a discount to the then-current market price of the common units into which they were convertible. This discount, totaling $34.8 million , represented a beneficial conversion feature, and at issuance, was reflected as an increase in WES Operating common unitholders’ capital and a decrease in Class C unitholder capital to reflect the fair value of the Class C units at issuance. The beneficial conversion feature was considered a non-cash distribution that was recognized from the date of issuance through the date of conversion, resulting in an increase in Class C unitholder capital and a decrease in common unitholders’ capital as amortized. The beneficial conversion feature was amortized assuming the extended conversion date of March 1, 2020, using the effective yield method. The impact of the beneficial conversion feature amortization was included in the calculation of earnings per unit (see WES Operating’s net income (loss) per common unit below). All outstanding Class C units converted into WES Operating common units on a one -for-one basis immediately prior to the closing of the Merger (see Note 1 ). Partnership’s net income (loss) per common unit. The Partnership’s net income (loss) per common unit is calculated by dividing the limited partners’ interest in net income (loss) by the weighted-average number of common units outstanding during the period. Net income (loss) per common unit is calculated assuming that cash distributions are equal to the net income attributable to the Partnership. Net income (loss) attributable to the Partnership assets (as defined in Note 1 ) acquired from Anadarko for periods prior to the acquisition of the assets is not allocated to the limited partners when calculating net income (loss) per common unit. Net income equal to the amount of available cash (as defined by the partnership agreement) is allocated to the Partnership’s common unitholders consistent with actual cash distributions. WES Operating’s net income (loss) per common unit. For periods subsequent to the closing of the Merger, net income (loss) per common unit for WES Operating is not calculated as it no longer has publicly traded units. For periods prior to the closing of the Merger, Net income (loss) attributable to Western Midstream Operating, LP earned on and subsequent to the date of acquisition of the Partnership assets was allocated as discussed below. Net income (loss) attributable to the Partnership assets acquired from Anadarko for periods prior to the acquisition of the assets was not allocated to the unitholders for purposes of calculating net income (loss) per common unit. 5. EQUITY AND PARTNERS’ CAPITAL (CONTINUED) General partner. The general partner’s allocation was equal to cash distributions plus its portion of undistributed earnings or losses. Specifically, net income equal to the amount of available cash (as defined by WES Operating’s partnership agreement) was allocated to the general partner consistent with actual cash distributions and capital account allocations, including incentive distributions. Undistributed earnings (net income in excess of distributions) or undistributed losses (available cash in excess of net income) was then allocated to the general partner in accordance with its weighted-average ownership percentage during each period. Common and Class C unitholders. The Class C units were considered a participating security because they participated in distributions with common units according to a predetermined formula (see Note 4 ). The common and Class C unitholders’ allocation was equal to their cash distributions plus their respective allocations of undistributed earnings or losses. Specifically, net income equal to the amount of available cash (as defined by the WES Operating partnership agreement) was allocated to the common and Class C unitholders consistent with actual cash distributions and capital account allocations. Undistributed earnings or undistributed losses were then allocated to the common and Class C unitholders in accordance with their respective weighted-average ownership percentages during each period. The common unitholder allocation also included the impact of the amortization of the Class C units beneficial conversion feature. The Class C unitholder allocation was similarly impacted by the amortization of the Class C units beneficial conversion feature (see WES Operating Class C units above). Calculation of net income (loss) per unit. Basic net income (loss) per common unit was calculated by dividing the net income (loss) attributable to common unitholders by the weighted-average number of common units outstanding during the period. The common units issued in connection with acquisitions and equity offerings were included on a weighted-average basis for periods they were outstanding. Diluted net income (loss) per common unit was calculated by dividing the sum of (i) the net income (loss) attributable to common units and (ii) the net income (loss) attributable to the Class C units as a participating security, by the sum of the weighted-average number of common units outstanding plus the dilutive effect of the weighted-average number of outstanding Class C units. The following table illustrates the calculation of WES Operating’s net income (loss) per common unit: Three Months Ended thousands except per-unit amounts 2018 Net income (loss) attributable to Western Midstream Operating, LP $ 179,885 Pre-acquisition net (income) loss allocated to Anadarko (30,522 ) General partner interest in net (income) loss (83,439 ) Common and Class C limited partners’ interest in net income (loss) $ 65,924 Net income (loss) allocable to common units (1) $ 58,323 Net income (loss) allocable to Class C units (1) 7,601 Common and Class C limited partners’ interest in net income (loss) $ 65,924 Net income (loss) per unit Common units – basic and diluted (2) $ 0.38 Weighted-average units outstanding Common units – basic and diluted 152,602 Excluded due to anti-dilutive effect: Class C units (2) 13,380 (1) Adjusted to reflect amortization of the beneficial conversion feature. (2) The impact of Class C units would be anti-dilutive for the period presented.

Transactions with Affiliates

Transactions with Affiliates	3 Months Ended
	Mar. 31, 2019
Related Party Fees and Other Arrangements, Limited Liability Company (LLC) or Limited Partnership (LP) [Abstract]
Transactions with Affiliates	6. TRANSACTIONS WITH AFFILIATES Affiliate transactions. Revenues from affiliates include amounts earned by the Partnership from services provided to Anadarko as well as from the sale of natural gas, condensate and NGLs to Anadarko. Anadarko sells such natural gas, condensate and NGLs as an agent on behalf of either the Partnership or the Partnership’s customers. When such sales are on the Partnership’s customers’ behalf, the Partnership recognizes associated service revenues and cost of product expense. When such sales are on the Partnership’s behalf, the Partnership recognizes product sales revenues based on the Anadarko sales price to the third party and cost of product expense associated with these sales activities. In addition, the Partnership purchases natural gas, condensate and NGLs from an affiliate of Anadarko pursuant to gas purchase agreements. Operation and maintenance expense includes amounts accrued for or paid to affiliates for the operation of the Partnership assets, whether in providing services to affiliates or to third parties, including field labor, measurement and analysis, and other disbursements. A portion of general and administrative expenses is paid by Anadarko, which results in affiliate transactions pursuant to the reimbursement provisions of the omnibus agreements of the Partnership and WES Operating. Affiliate expenses do not bear a direct relationship to affiliate revenues, and third-party expenses do not bear a direct relationship to third-party revenues. Merger transactions. As discussed in more detail in Note 1 , on February 28, 2019, the Partnership, WES Operating, Anadarko and certain of their affiliates consummated the Merger and the other transactions contemplated in the Merger Agreement, which included the acquisition of AMA from Anadarko. See Note 3 . Cash management. Anadarko operates a cash management system whereby excess cash from most of its subsidiaries’ separate bank accounts is generally swept to centralized accounts. Prior to the acquisition of Partnership assets, third-party sales and purchases related to such assets were received or paid in cash by Anadarko within its centralized cash management system. The outstanding affiliate balances were entirely settled through an adjustment to net investment by Anadarko in connection with the acquisition of the Partnership assets. Subsequent to the acquisition of Partnership assets from Anadarko, transactions related to such assets are cash-settled directly with third parties and with Anadarko affiliates. Chipeta cash settles its transactions directly with third parties and Anadarko, as well as with the other subsidiaries of the Partnership. Note receivable - Anadarko. In May 2008, WES Operating loaned $260.0 million to Anadarko in exchange for a 30-year note bearing interest at a fixed annual rate of 6.50% , payable quarterly. The fair value of the note receivable from Anadarko was $303.9 million and $279.6 million at March 31, 2019 , and December 31, 2018 , respectively. The fair value of the note reflects consideration of credit risk and any premium or discount for the differential between the stated interest rate and quarter-end market interest rate, based on quoted market prices of similar debt instruments. Accordingly, the fair value of the note receivable from Anadarko is measured using Level 2 inputs. APCWH Note Payable. In June 2017, APCWH entered into an eight-year note payable agreement with Anadarko, which was repaid upon consummation of the Merger. See Note 1 and Note 10 . Commodity price swap agreements. WES Operating had commodity price swap agreements with Anadarko to mitigate exposure to the commodity price risk inherent in its percent-of-proceeds, percent-of-product and keep-whole contracts. Notional volumes for each of the commodity price swap agreements were not specifically defined. Instead, the commodity price swap agreements applied to the actual volume of natural gas, condensate and NGLs purchased and sold. The commodity price swap agreements did not satisfy the definition of a derivative financial instrument and, therefore, were not required to be measured at fair value. Net gains (losses) on commodity price swap agreements were $(0.7) million (due to settlement of 2018 activity in 2019) and $(1.2) million for the three months ended March 31, 2019 and 2018 , respectively, and are reported in the consolidated statements of operations as affiliate Product sales. These commodity price swap agreements expired without renewal on December 31, 2018. 6. TRANSACTIONS WITH AFFILIATES (CONTINUED) Revenues or costs attributable to volumes sold and purchased during 2018 and/or settled during 2019 for the DJ Basin complex and the MGR assets are recognized in the consolidated statements of operations at the applicable market price in the tables below. A capital contribution from Anadarko is recorded in the consolidated statements of equity and partners’ capital for an amount equal to (i) the amount by which the swap price for product sales exceeds the applicable market price in the tables below, minus (ii) the amount by which the swap price for product purchases exceeds the applicable market price in the tables below. For the three months ended March 31, 2019 and 2018 , the capital contributions from Anadarko were $7.4 million (due to settlement of 2018 activity in 2019) and $14.3 million , respectively. The tables below summarize the swap prices compared to the forward market prices: DJ Basin Complex per barrel except natural gas 2018 Swap Prices 2018 Market Prices (1) Ethane $ 18.41 $ 5.41 Propane 47.08 28.72 Isobutane 62.09 32.92 Normal butane 54.62 32.71 Natural gasoline 72.88 48.04 Condensate 76.47 49.36 Natural gas (per MMBtu) 5.96 2.21 MGR Assets per barrel except natural gas 2018 Swap Prices 2018 Market Prices (1) Ethane $ 23.11 $ 2.52 Propane 52.90 25.83 Isobutane 73.89 30.03 Normal butane 64.93 29.82 Natural gasoline 81.68 47.25 Condensate 81.68 56.76 Natural gas (per MMBtu) 4.87 2.21 (1) Represents the New York Mercantile Exchange forward strip price as of December 20, 2017, for the 2018 Market Prices, adjusted for product specification, location, basis and, in the case of NGLs, transportation and fractionation costs. 6. TRANSACTIONS WITH AFFILIATES (CONTINUED) Gathering and processing agreements. The Partnership has significant gathering and processing arrangements with affiliates of Anadarko on a majority of its systems. Natural gas gathering, treating and transportation throughput (excluding equity investment throughput) attributable to production owned or controlled by Anadarko was 6% and 7% for the three months ended March 31, 2019 and 2018 , respectively. Natural gas processing throughput (excluding equity investment throughput) attributable to production owned or controlled by Anadarko was 41% and 40% for the three months ended March 31, 2019 and 2018 , respectively. Crude oil, NGLs and produced water gathering, treating, transportation and disposal throughput (excluding equity investment throughput) attributable to production owned or controlled by Anadarko was 83% and 79% for the three months ended March 31, 2019 and 2018 , respectively. Commodity purchase and sale agreements. The Partnership sells a significant amount of its natural gas, condensate and NGLs to Anadarko Energy Services Company (“AESC”), Anadarko’s marketing affiliate that acts as an agent in the sale to a third party. In addition, the Partnership purchases natural gas, condensate and NGLs from AESC pursuant to purchase agreements. The purchase and sale agreements with AESC are generally one-year contracts, subject to annual renewal. LTIPs. The general partner awards phantom units under the Western Gas Partners, LP 2017 Long-Term Incentive Plan (assumed by the Partnership in connection with the Merger) and the Western Gas Equity Partners, LP 2012 Long-Term Incentive Plan (collectively referred to as the “LTIPs”) to its independent directors, but also from time to time to the executive officers and Anadarko employees performing services for the Partnership. The phantom units awarded to the independent directors vest one year from the grant date, while all other awards are subject to graded vesting over a three -year service period. Anadarko Incentive Plan. General and administrative expenses included equity-based compensation expense allocated to the Partnership by Anadarko, for awards granted to the executive officers of the general partner and other employees under the Anadarko Petroleum Corporation 2012 Omnibus Incentive Compensation Plan, as amended and restated (the “Anadarko Incentive Plan”). Portions of these amounts are reflected as contributions to partners’ capital in the consolidated statements of equity and partners’ capital. 6. TRANSACTIONS WITH AFFILIATES (CONTINUED) Summary of affiliate transactions. The following table summarizes material affiliate transactions included in the Partnership’s consolidated financial statements: Three Months Ended thousands 2019 2018 Revenues and other (1) $ 378,437 $ 285,176 Equity income, net – affiliates (1) 57,992 30,229 Cost of product (1) 56,172 34,819 Operation and maintenance (1) 39,141 23,001 General and administrative (2) 18,894 12,688 Operating expenses 114,207 70,508 Interest income (3) 4,225 4,225 Interest expense (4) 1,833 577 APCWH Note Payable borrowings (5) 11,000 106,565 Repayment of APCWH Note Payable (5) 439,595 — Distributions to Partnership unitholders (6) 102,654 98,000 Distributions to WES Operating unitholders (7) 2,543 1,850 Above-market component of swap agreements with Anadarko 7,407 14,282 (1) 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. (2) Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6 ) and amounts charged by Anadarko under the omnibus agreements of the Partnership and WES Operating. (3) Represents interest income recognized on the note receivable from Anadarko. (4) Includes amounts related to the APCWH Note Payable (see Note 1 and Note 10 ) . (5) See Note 1 . (6) Represents distributions paid to Anadarko under the partnership agreement of the Partnership (see Note 4 and Note 5 ). (7) Represents distributions paid to other subsidiaries of Anadarko under WES Operating’s partnership agreement (see Note 4 and Note 5 ). The following table summarizes affiliate transactions for WES Operating (which are included in the Partnership’s consolidated financial statements) to the extent the amounts differ from the Partnership’s consolidated financial statements: Three Months Ended thousands 2019 2018 General and administrative (1) $ 18,498 $ 12,479 Distributions to WES Operating unitholders (2) 164,902 124,164 (1) Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to WES Operating by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6 ) and amounts charged by Anadarko under the omnibus agreement of WES Operating. (2) 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 ). 6. TRANSACTIONS WITH AFFILIATES (CONTINUED) Concentration of credit risk. Anadarko was the only customer from whom revenues exceeded 10% of consolidated revenues for all periods presented in the consolidated statements of operations.

Property, Plant and Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	7. PROPERTY, PLANT AND EQUIPMENT A summary of the historical cost of property, plant and equipment is as follows: thousands Estimated Useful Life March 31, December 31, Land n/a $ 8,858 $ 5,298 Gathering systems – pipelines 30 years 4,828,320 4,764,099 Gathering systems – compressors 15 years 1,809,009 1,712,939 Processing complexes and treating facilities 25 years 2,944,387 2,844,337 Transportation pipeline and equipment 6 to 45 years 172,637 172,558 Produced water disposal systems 20 years 667,106 629,946 Assets under construction n/a 603,234 604,265 Other 3 to 40 years 546,778 525,331 Total property, plant and equipment 11,580,329 11,258,773 Less accumulated depreciation 2,950,330 2,848,420 Net property, plant and equipment $ 8,629,999 $ 8,410,353 The cost of property classified as “Assets under construction” is excluded from capitalized costs being depreciated. These amounts represent property that is not yet suitable to be placed into productive service as of the respective balance sheet date. Impairments. During the three months ended March 31, 2019 , the Partnership recognized impairments of $0.4 million . During the year ended December 31, 2018, the Partnership recognized impairments of $230.6 million , including impairments of $125.9 million at the Third Creek gathering system and $8.1 million at the Kitty Draw gathering system. These assets were impaired to their estimated salvage values of $1.8 million and zero , respectively, using the market approach and Level 3 fair value inputs, due to the shutdown of the systems in May 2018. Also during 2018, the Partnership recognized impairments of $38.7 million and $34.6 million at the Hilight and MIGC systems, respectively. These assets were impaired to their estimated fair values of $4.9 million and $15.2 million , respectively, using the income approach and Level 3 fair value inputs, due to a reduction in estimated future cash flows. The remaining $23.3 million of impairments was primarily related to (i) a $10.9 million impairment at the GNB NGL pipeline, which was impaired to its estimated fair value of $10.0 million using the income approach and Level 3 fair value inputs, and (ii) a $5.6 million impairment related to an idle facility at the Chipeta complex, which was impaired to its estimated salvage value of $1.5 million using the market approach and Level 3 fair value inputs.

Equity Investments

Equity Investments	3 Months Ended
	Mar. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Equity Investments	8. EQUITY INVESTMENTS The following table presents the equity investments activity for the three months ended March 31, 2019 : thousands Balance at December 31, 2018 Acquisitions Equity income, net Contributions (1) Distributions Distributions in excess of cumulative earnings (2) Balance at March 31, 2019 Fort Union $ 2,259 $ — $ (573 ) $ — $ — $ (237 ) $ 1,449 White Cliffs 43,020 — 3,225 1,845 (3,079 ) (935 ) 44,076 Rendezvous 37,841 — 121 — (607 ) (671 ) 36,684 Mont Belvieu JV 104,949 — 7,127 — (4,500 ) — 107,576 TEG 19,358 — 830 — (835 ) (316 ) 19,037 TEP 193,198 — 8,665 6,000 (9,865 ) — 197,998 FRP 176,436 — 7,125 — (6,480 ) — 177,081 Whitethorn LLC 161,858 — 21,860 3,228 (17,058 ) (5,213 ) 164,675 Cactus II 106,360 — — 17,791 — — 124,151 Saddlehorn 108,507 — 4,830 — (5,189 ) — 108,148 Panola 22,769 — 582 — (582 ) (228 ) 22,541 Mi Vida 64,632 — 1,685 — (2,451 ) — 63,866 Ranch Westex 50,901 — 2,027 — (3,087 ) (132 ) 49,709 Red Bluff Express — 92,546 488 7,679 (488 ) (60 ) 100,165 Total $ 1,092,088 $ 92,546 $ 57,992 $ 36,543 $ (54,221 ) $ (7,792 ) $ 1,217,156 (1) Includes capitalized interest of $1.5 million related to the construction of the pipeline owned by Cactus II. (2) 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.

Components of Working Capital

Components of Working Capital	3 Months Ended
	Mar. 31, 2019
Components Of Working Capital [Abstract]
Components of Working Capital	9. COMPONENTS OF WORKING CAPITAL A summary of accounts receivable, net is as follows: The Partnership WES Operating thousands March 31, December 31, March 31, December 31, Trade receivables, net $ 212,342 $ 221,119 $ 214,067 $ 221,328 Other receivables, net 81 45 81 45 Total accounts receivable, net $ 212,423 $ 221,164 $ 214,148 $ 221,373 A summary of other current assets is as follows: The Partnership WES Operating thousands March 31, December 31, March 31, December 31, NGLs inventory $ 6,861 $ 6,466 $ 6,861 $ 6,466 Imbalance receivables 5,800 9,035 5,800 9,035 Prepaid insurance 1,064 1,972 1,026 1,972 Contract assets 7,172 5,399 7,172 5,399 Other 2,575 4,184 2,575 3,309 Total other current assets $ 23,472 $ 27,056 $ 23,434 $ 26,181 A summary of accrued liabilities is as follows: The Partnership WES Operating thousands March 31, December 31, March 31, December 31, Accrued interest expense $ 55,831 $ 70,968 $ 55,831 $ 70,959 Short-term asset retirement obligations 23,033 25,938 23,033 25,938 Short-term remediation and reclamation obligations 863 863 863 863 Income taxes payable 861 384 861 384 Contract liabilities 6,364 16,235 6,364 16,235 Other (1) 54,490 14,760 54,315 13,495 Total accrued liabilities $ 141,442 $ 129,148 $ 141,267 $ 127,874 (1) Includes amounts related to WES Operating’s interest-rate swaps as of March 31, 2019 and December 31, 2018 (see Note 10 ). Includes lease liabilities related to the implementation of ASU 2016-02, Leases (Topic 842) as of March 31, 2019 (see Note 1 ).

Debt and Interest Expense

Debt and Interest Expense	3 Months Ended
	Mar. 31, 2019
Debt Instruments [Abstract]
Debt and Interest Expense	10. DEBT AND INTEREST EXPENSE WES Operating is the borrower for all existing debt, excluding the WGP RCF, and is expected to be the borrower for all future debt. The following table presents the outstanding debt: March 31, 2019 December 31, 2018 thousands Principal Carrying Value Fair Value (1) Principal Carrying Value Fair Value (1) Short-term debt WGP RCF $ — $ — $ — $ 28,000 $ 28,000 $ 28,000 364-day Facility 2,000,000 2,000,000 2,000,000 — — — Total short-term debt $ 2,000,000 $ 2,000,000 $ 2,000,000 $ 28,000 $ 28,000 $ 28,000 Long-term debt 5.375% Senior Notes due 2021 $ 500,000 $ 497,257 $ 518,755 $ 500,000 $ 496,959 $ 515,990 4.000% Senior Notes due 2022 670,000 669,138 680,293 670,000 669,078 662,109 3.950% Senior Notes due 2025 500,000 493,082 493,788 500,000 492,837 466,135 4.650% Senior Notes due 2026 500,000 495,830 507,034 500,000 495,710 483,994 4.500% Senior Notes due 2028 400,000 394,749 400,050 400,000 394,631 377,475 4.750% Senior Notes due 2028 400,000 395,928 407,849 400,000 395,841 384,370 5.450% Senior Notes due 2044 600,000 593,378 573,949 600,000 593,349 522,386 5.300% Senior Notes due 2048 700,000 686,696 664,278 700,000 686,648 605,327 5.500% Senior Notes due 2048 350,000 342,353 341,536 350,000 342,328 311,536 RCF 640,000 640,000 640,000 220,000 220,000 220,000 APCWH Note Payable — — — 427,493 427,493 427,493 Total long-term debt $ 5,260,000 $ 5,208,411 $ 5,227,532 $ 5,267,493 $ 5,214,874 $ 4,976,815 (1) Fair value is measured using the market approach and Level 2 inputs. Debt activity. The following table presents the debt activity for the three months ended March 31, 2019 : thousands Carrying Value Balance at December 31, 2018 $ 5,242,874 RCF borrowings 420,000 364-day Facility borrowings 2,000,000 APCWH Note Payable borrowings 11,000 Repayment of WGP RCF borrowings (28,000 ) Repayment of APCWH Note Payable (439,595 ) Other 2,132 Balance at March 31, 2019 $ 7,208,411 WES Operating Senior Notes. At March 31, 2019 , WES Operating was in compliance with all covenants under the indentures governing its outstanding notes. WGP RCF. In February 2018, the Partnership voluntarily reduced the aggregate commitments of the lenders under the WGP RCF to $35.0 million . The WGP R CF, which was previously available to be used to buy WES Operating common units and for general partnership purposes, matured in March 2019 and the $28.0 million of outstanding borrowings were repaid. 10. DEBT AND INTEREST EXPENSE (CONTINUED) Revolving credit facility. In December 2018, WES Operating entered into an amendment to the senior unsecured revolving credit facility (“RCF”) that (i) subject to the consummation of the Merger (see Note 1 ), increased the size of the RCF from $1.5 billion to $2.0 billion , while leaving the $0.5 billion accordion feature of the RCF unexercised, and (ii) effective on February 15, 2019, exercised one of the one-year extension options to extend the maturity date of the RCF from February 2023 to February 2024. The RCF is expandable to a maximum of $2.5 billion and bears interest at the London Interbank Offered Rate (“LIBOR”), plus applicable margins ranging from 1.00% to 1.50% , or an alternate base rate equal to the greatest of (a) the Prime Rate, (b) the Federal Funds Effective Rate plus 0.50% , or (c) LIBOR plus 1.00% , in each case plus applicable margins currently ranging from zero to 0.50% , based upon WES Operating’s senior unsecured debt rating. A required quarterly facility fee is paid ranging from 0.125% to 0.250% of the commitment amount (whether used or unused), also based upon the senior unsecured debt rating. As of March 31, 2019 , there was $640.0 million in outstanding borrowings and $4.6 million in outstanding letters of credit, resulting in $1.4 billion available borrowing capacity under the RCF. As of March 31, 2019 and 2018 , the interest rate on any outstanding RCF borrowings was 3.79% and 3.18% , respectively. The facility fee rate was 0.20% at March 31, 2019 and 2018 . At March 31, 2019 , WES Operating was in compliance with all covenants under the RCF. 364-day Facility. In December 2018, WES Operating entered into a $2.0 billion 364-day senior unsecured credit facility (the “364-day Facility”), the proceeds of which were used to fund substantially all of the cash portion of the consideration under the Merger Agreement and the payment of related transaction costs (see Note 1 ). The 364-day Facility will mature in February 2020, and bears interest at LIBOR, plus applicable margins ranging from 1.000% to 1.625% , or an alternate base rate equal to the greatest of (a) the Prime Rate, (b) the Federal Funds Effective Rate plus 0.50% , or (c) LIBOR plus 1.00% , in each case as defined in the 364-day Facility and plus applicable margins currently ranging from zero to 0.625% , based upon WES Operating’s senior unsecured debt rating. Net cash proceeds received from future asset sales and debt or equity offerings must be used to repay amounts outstanding under the facility. As of March 31, 2019 , there was $2.0 billion in outstanding borrowings under the 364-day Facility. As of March 31, 2019 , the interest rate on outstanding 364-day Facility borrowings was 3.87% and WES Operating was in compliance with all covenants under the 364-day Facility. The 364-day Facility was classified as short-term debt on the consolidated balance sheets at March 31, 2019 . All of WES Operating’s notes and obligations under the RCF and 364-day facility are recourse to WES Operating GP. WES Operating GP is indemnified by wholly owned subsidiaries of Anadarko against any claims made against WES Operating GP for WES Operating’s long-term debt and/or borrowings under the RCF and 364-day Facility. APCWH Note Payable. In June 2017, in connection with funding the construction of the APC water systems, which were acquired as part of the AMA acquisition, APCWH entered into an eight-year note payable agreement with Anadarko. This note payable had a maximum borrowing limit of $500.0 million , and accrued interest, which was payable upon maturity, at the applicable mid-term federal rate based on a quarterly compounding basis as determined by the U.S. Secretary of the Treasury. As of March 31, 2018, the interest rate on the outstanding borrowings was 2.54% . The APCWH Note Payable was repaid upon the consummation of the Merger. See Note 1 and Note 6 . 10. DEBT AND INTEREST EXPENSE (CONTINUED) Interest-rate swaps. In December 2018 and March 2019, WES Operating entered into interest-rate swap agreements with an aggregate notional amount of $750.0 million and $375.0 million , respectively, to manage interest rate risk associated with anticipated 2019 debt issuances. Pursuant to these swap agreements, a floating interest rate indexed to the three-month LIBOR was exchanged for a fixed interest rate. Depending on market conditions, liability management actions or other factors, WES Operating may settle or amend certain or all of the currently outstanding interest-rate swaps. The following interest-rate swaps were outstanding as of March 31, 2019 : Notional Principal Amount Reference Period Mandatory Termination Date Weighted-Average Interest Rate $375.0 million December 2019 - 2024 December 2019 2.662% $375.0 million December 2019 - 2029 December 2019 2.802% $375.0 million December 2019 - 2049 December 2019 2.885% The Partnership does not apply hedge accounting and, therefore, gains and losses associated with the interest-rate swaps are recognized currently in earnings. For the three months ended March 31, 2019 , a non-cash loss of $35.6 million was recognized, which is included in Other income (expense), net in the consolidated statements of operations. Valuation of the interest-rate swaps is based on similar transactions observable in active markets and industry standard models that primarily rely on market-observable inputs. Inputs used to estimate fair value in industry standard models are categorized as Level 2 inputs, because substantially all assumptions and inputs are observable in active markets throughout the full term of the instruments. Inputs used to estimate the fair value include market price curves, contract terms and prices, and credit risk adjustments. The fair value of the interest-rate swaps was a liability of $43.6 million and $8.0 million at March 31, 2019 , and December 31, 2018 , respectively, which is reported in Accrued liabilities on the consolidated balance sheets. Credit risk considerations. Over-the-counter traded swaps expose the Partnership to counterparty credit risk. The Partnership monitors the creditworthiness of its counterparties, establishes credit limits according to credit policies and guidelines, and assesses the impact on the fair value of its counterparties’ creditworthiness. Under certain circumstances, the Partnership has the ability to require cash collateral or letters of credit to mitigate its credit risk exposure. The interest-rate swaps are subject to individually negotiated credit provisions that may require collateral of cash or letters of credit depending on the derivative’s portfolio valuation versus negotiated credit thresholds. These credit thresholds generally require full or partial collateralization of the Partnership’s obligations depending on certain credit risk related provisions. Specifically, collateral may be required to be posted with respect to the interest-rate swaps if WES Operating’s credit ratings decline below current levels, the liability associated with the swaps increases substantially or certain credit event of default provisions occur. For example, based on the derivative positions as of March 31, 2019 , if WES Operating’s credit ratings from both Standard and Poor’s and Moody’s Investors Service were below the investment grade thresholds of BBB- and Baa3, respectively, collateral would be required to be posted of up to approximately $18.6 million as of March 31, 2019 . The aggregate fair value of interest-rate swaps with credit risk related contingent features for which a net liability position existed was $35.1 million and $5.7 million at March 31, 2019 , and December 31, 2018 , respectively. 10. DEBT AND INTEREST EXPENSE (CONTINUED) Interest expense. The following table summarizes the amounts included in interest expense: Three Months Ended thousands 2019 2018 Third parties Long-term and short-term debt $ (67,096 ) $ (41,536 ) Amortization of debt issuance costs and commitment fees (3,152 ) (2,864 ) Capitalized interest 6,205 6,962 Total interest expense – third parties (64,043 ) (37,438 ) Affiliates APCWH Note Payable (1,833 ) (577 ) Total interest expense – affiliates (1,833 ) (577 ) Interest expense $ (65,876 ) $ (38,015 )

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	11. LEASES Anadarko, on behalf of the Partnership, has entered into operating leases for corporate offices, shared field offices, and equipment supporting the Partnership’s operations, for which Anadarko charges the Partnership rent. The leases for the corporate offices and shared field offices extend through 2028. Total lease cost, net of sublease income of $0.1 million , was $1.8 million for the three months ended March 31, 2019 . Variable lease cost was immaterial for the three months ended March 31, 2019 . Lease expense charged to the Partnership was $13.8 million for the three months ended March 31, 2018. Operating cash payments for amounts included in the measurement of lease liabilities was $2.0 million for the three months ended March 31, 2019. The following table summarizes other information related to operating leases: thousands except lease term and discount rate March 31, 2019 Lease assets Other assets $ 10,002 Lease liabilities Accrued liabilities 7,560 Other liabilities 3,343 Weighted-average remaining lease term (years) 4 Weighted-average discount rate 4.1 % 11. LEASES (CONTINUED) The following table reconciles the undiscounted cash flows to the operating lease liabilities at March 31, 2019 , that may be assigned or otherwise charged to the Partnership pursuant to the reimbursement provisions of the omnibus agreement: thousands Remainder of 2019 $ 5,588 2020 2,215 2021 612 2022 618 2023 625 Thereafter 1,658 Total lease payments 11,316 Less portion representing imputed interest 413 Total lease liabilities $ 10,903 The amounts in the table below represent contractual operating lease commitments at December 31, 2018 , that may be assigned or otherwise charged to the Partnership pursuant to the reimbursement provisions of the omnibus agreement: thousands 2019 $ 8,711 2020 2,236 2021 460 2022 467 2023 473 Thereafter 1,547 Total lease payments $ 13,894

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	12. COMMITMENTS AND CONTINGENCIES Litigation and legal proceedings. From time to time, the Partnership is involved in legal, tax, regulatory and other proceedings in various forums regarding performance, contracts and other matters that arise in the ordinary course of business. Management is not aware of any such proceeding for which the final disposition could have a material adverse effect on the Partnership’s financial condition, results of operations or cash flows. Other commitments. The Partnership has short-term payment obligations, or commitments, related to its capital spending programs, as well as those of its unconsolidated affiliates, the majority of which is expected to be paid in the next twelve months. These commitments primarily relate to construction and expansion projects at the West Texas and DJ Basin complexes, DBM oil system and DBM water systems.

Description of Business and B_2

Description of Business and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Consolidation policy	Basis of presentation. The following table outlines the ownership interests and the accounting method of consolidation used in the consolidated financial statements for entities not wholly owned: Percentage Interest Equity investments (1) Fort Union 14.81 % White Cliffs 10.00 % Rendezvous 22.00 % Mont Belvieu JV 25.00 % TEP 20.00 % TEG 20.00 % FRP 33.33 % Whitethorn LLC 20.00 % Cactus II 15.00 % Saddlehorn 20.00 % Panola 15.00 % Mi Vida 50.00 % Ranch Westex 50.00 % Red Bluff Express 30.00 % Proportionate consolidation (2) Marcellus Interest systems 33.75 % Springfield system 50.10 % Full consolidation Chipeta (3) 75.00 % (1) Investments in non-controlled entities over which the Partnership exercises significant influence are accounted for under the equity method. “Equity investment throughput” refers to the Partnership’s share of average throughput for these investments. (2) The Partnership proportionately consolidates its associated share of the assets, liabilities, revenues and expenses attributable to these assets. (3) The 25% interest in Chipeta Processing LLC (“Chipeta”) held by a third-party member is reflected within noncontrolling interests in the consolidated financial statements, in addition to the noncontrolling interests noted below. The consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”). The consolidated financial statements include the accounts of the Partnership and entities in which it holds a controlling financial interest, including WES Operating and WES Operating GP. All significant intercompany transactions have been eliminated. Certain information and note disclosures commonly included in annual financial statements have been condensed or omitted pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). Accordingly, the accompanying consolidated financial statements and notes should be read in conjunction with the Partnership and WES Operating’s 2018 Forms 10-K, as filed with the SEC on February 20, 2019 . 1. DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (CONTINUED) The consolidated financial results of WES Operating are included in the Partnership’s consolidated financial statements. Throughout these notes to consolidated financial statements, and to the extent material, any differences between the consolidated financial results of the Partnership and WES Operating are discussed separately. The Partnership’s consolidated financial statements differ from those of WES Operating primarily as a result of (i) the presentation of noncontrolling interest ownership (see Noncontrolling interests below and Note 5 ), (ii) the elimination of WES Operating GP’s investment in WES Operating with WES Operating GP’s underlying capital account, (iii) the general and administrative expenses incurred by the Partnership, which are separate from, and in addition to, those incurred by WES Operating, (iv) the inclusion of the impact of Partnership equity balances and Partnership distributions, and (v) the senior secured revolving credit facility (“WGP RCF”) until its repayment in March 2019. See Note 10 . Noncontrolling interests. For periods subsequent to the consummation of the Merger, the Partnership’s noncontrolling interests in the consolidated financial statements consisted of (i) the 25% interest in Chipeta held by a third-party member and (ii) the 2.0% limited partner interest in WES Operating held by a subsidiary of Anadarko. For periods prior to the consummation of the Merger, the Partnership’s noncontrolling interests in the consolidated financial statements consisted of (i) the 25% interest in Chipeta held by a third-party member, (ii) the publicly held limited partner interests in WES Operating, (iii) the common units issued by WES Operating to subsidiaries of Anadarko as part of the consideration paid for prior acquisitions from Anadarko, and (iv) the Class C units issued by WES Operating to a subsidiary of Anadarko as part of the funding for the acquisition of DBM. For all periods presented, WES Operating’s noncontrolling interest in the consolidated financial statements consisted of the 25% interest in Chipeta held by a third-party member. See Note 5 . When WES Operating issues equity, the carrying amount of the noncontrolling interest reported by the Partnership is adjusted to reflect the noncontrolling ownership interest in WES Operating. The resulting impact of such noncontrolling interest adjustment on the Partnership’s interest in WES Operating is reflected as an adjustment to the Partnership’s partners’ capital.
Business combinations policy	Presentation of Partnership assets. The term “Partnership assets” includes both the assets owned and the interests accounted for under the equity method by the Partnership, through its partnership interests in WES Operating as of March 31, 2019 (see Note 8 ). Because the Partnership owns the entire non-economic general partner interest in and controls WES Operating GP, and the general partner is controlled by Anadarko, each of the Partnership’s acquisitions of assets from Anadarko has been considered a transfer of net assets between entities under common control. As such, assets acquired from Anadarko were initially recorded at Anadarko’s historic carrying value, which did not correlate to the total acquisition price paid by the Partnership. Further, after an acquisition of assets from Anadarko, the Partnership is required to recast its financial statements to include the activities of such assets from the date of common control. For those periods requiring recast, the consolidated financial statements for periods prior to the acquisition of assets from Anadarko are prepared from Anadarko’s historical cost-basis accounts and may not necessarily be indicative of the actual results of operations that would have occurred if the Partnership had owned the assets during the periods reported. Net income (loss) attributable to the assets acquired from Anadarko for periods prior to the Partnership’s acquisition of such assets is not allocated to the limited partners.
Use of estimates policy	Use of estimates. In preparing financial statements in accordance with GAAP, management makes informed judgments and estimates that affect the reported amounts of assets, liabilities, revenues and expenses. Management evaluates its estimates and related assumptions regularly, using historical experience and other methods considered reasonable. Changes in facts and circumstances or additional information may result in revised estimates and actual results may differ from these estimates. Effects on the business, financial condition and results of operations resulting from revisions to estimates are recognized when the facts that give rise to the revisions become known. The information included herein reflects all normal recurring adjustments which are, in the opinion of management, necessary for a fair presentation of the consolidated financial statements, and certain prior-period amounts have been reclassified to conform to the current-year presentation.
Segments policy	Segments. The Partnership’s operations continue to be organized into a single operating segment, the assets of which gather, compress, treat, process and transport natural gas; gather, stabilize and transport condensate, NGLs and crude oil; and gather and dispose of produced water in the United States.
New accounting standards policy	Recently adopted accounting standards. ASU 2016-02, Leases (Topic 842) requires lessees to recognize a lease liability and a right-of-use (“ROU”) asset for all leases, including operating leases, with a term greater than 12 months on the balance sheet. This ASU modifies the definition of a lease and outlines the recognition, measurement, presentation, and disclosure of leasing arrangements by both lessees and lessors. The Partnership adopted this standard on January 1, 2019, using the modified retrospective method applied to all leases that existed on January 1, 2019, and prior-period financial statements were not adjusted. The Partnership elected not to reassess contracts that commenced prior to adoption, to continue applying its current accounting policy for existing or expired land easements and not to recognize ROU assets or lease liabilities for short-term leases.
Leases policy	Leases. The Partnership determines if an arrangement is a lease based on rights and obligations conveyed at inception of a contract. Operating leases are included in other assets, accrued liabilities and other liabilities on the consolidated balance sheets. ROU assets and lease liabilities are recognized at the commencement date based on the present value of future lease payments over the lease term. As the rate implicit in the Partnership’s leases is generally not readily determinable, the Partnership discounts lease liabilities using the Partnership’s incremental borrowing rate at the commencement date. Non-lease components associated with leases that begin in 2019 or later are accounted for as part of the lease component, and prepaid lease payments are included in ROU assets. Options to extend or terminate a lease are included in the lease term when it is reasonably certain that the Partnership will exercise that option. Leases of 12 months or less are not recognized on the consolidated balance sheets. Lease cost is recognized over the lease term and is generally recognized on a straight-line basis. Variable lease payments are recognized when the obligation for those payments is incurred.
Net income (loss) per common unit policy	Partnership’s net income (loss) per common unit. The Partnership’s net income (loss) per common unit is calculated by dividing the limited partners’ interest in net income (loss) by the weighted-average number of common units outstanding during the period. Net income (loss) per common unit is calculated assuming that cash distributions are equal to the net income attributable to the Partnership. Net income (loss) attributable to the Partnership assets (as defined in Note 1 ) acquired from Anadarko for periods prior to the acquisition of the assets is not allocated to the limited partners when calculating net income (loss) per common unit. Net income equal to the amount of available cash (as defined by the partnership agreement) is allocated to the Partnership’s common unitholders consistent with actual cash distributions. WES Operating’s net income (loss) per common unit. For periods subsequent to the closing of the Merger, net income (loss) per common unit for WES Operating is not calculated as it no longer has publicly traded units. For periods prior to the closing of the Merger, Net income (loss) attributable to Western Midstream Operating, LP earned on and subsequent to the date of acquisition of the Partnership assets was allocated as discussed below. Net income (loss) attributable to the Partnership assets acquired from Anadarko for periods prior to the acquisition of the assets was not allocated to the unitholders for purposes of calculating net income (loss) per common unit. 5. EQUITY AND PARTNERS’ CAPITAL (CONTINUED) General partner. The general partner’s allocation was equal to cash distributions plus its portion of undistributed earnings or losses. Specifically, net income equal to the amount of available cash (as defined by WES Operating’s partnership agreement) was allocated to the general partner consistent with actual cash distributions and capital account allocations, including incentive distributions. Undistributed earnings (net income in excess of distributions) or undistributed losses (available cash in excess of net income) was then allocated to the general partner in accordance with its weighted-average ownership percentage during each period. Common and Class C unitholders. The Class C units were considered a participating security because they participated in distributions with common units according to a predetermined formula (see Note 4 ). The common and Class C unitholders’ allocation was equal to their cash distributions plus their respective allocations of undistributed earnings or losses. Specifically, net income equal to the amount of available cash (as defined by the WES Operating partnership agreement) was allocated to the common and Class C unitholders consistent with actual cash distributions and capital account allocations. Undistributed earnings or undistributed losses were then allocated to the common and Class C unitholders in accordance with their respective weighted-average ownership percentages during each period. The common unitholder allocation also included the impact of the amortization of the Class C units beneficial conversion feature. The Class C unitholder allocation was similarly impacted by the amortization of the Class C units beneficial conversion feature (see WES Operating Class C units above). Calculation of net income (loss) per unit. Basic net income (loss) per common unit was calculated by dividing the net income (loss) attributable to common unitholders by the weighted-average number of common units outstanding during the period. The common units issued in connection with acquisitions and equity offerings were included on a weighted-average basis for periods they were outstanding. Diluted net income (loss) per common unit was calculated by dividing the sum of (i) the net income (loss) attributable to common units and (ii) the net income (loss) attributable to the Class C units as a participating security, by the sum of the weighted-average number of common units outstanding plus the dilutive effect of the weighted-average number of outstanding Class C units.
Derivatives policy	The Partnership does not apply hedge accounting and, therefore, gains and losses associated with the interest-rate swaps are recognized currently in earnings. For the three months ended March 31, 2019 , a non-cash loss of $35.6 million was recognized, which is included in Other income (expense), net in the consolidated statements of operations. Valuation of the interest-rate swaps is based on similar transactions observable in active markets and industry standard models that primarily rely on market-observable inputs. Inputs used to estimate fair value in industry standard models are categorized as Level 2 inputs, because substantially all assumptions and inputs are observable in active markets throughout the full term of the instruments. Inputs used to estimate the fair value include market price curves, contract terms and prices, and credit risk adjustments. The fair value of the interest-rate swaps was a liability of $43.6 million and $8.0 million at March 31, 2019 , and December 31, 2018 , respectively, which is reported in Accrued liabilities on the consolidated balance sheets.

Description of Business and B_3

Description of Business and Basis of Presentation (Tables)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Assets and Investments Table	As of March 31, 2019 , the Partnership’s assets and investments consisted of the following: Owned and Operated Operated Interests Non-Operated Interests Equity Interests Gathering systems (1) 17 2 3 2 Treating facilities 35 3 — 3 Natural gas processing plants/trains 24 3 — 5 NGLs pipelines 2 — — 4 Natural gas pipelines 5 — — 1 Oil pipelines 3 1 — 3 (1) Includes the DBM water systems.
Ownership Interests and Method of Consolidation Table	The following table outlines the ownership interests and the accounting method of consolidation used in the consolidated financial statements for entities not wholly owned: Percentage Interest Equity investments (1) Fort Union 14.81 % White Cliffs 10.00 % Rendezvous 22.00 % Mont Belvieu JV 25.00 % TEP 20.00 % TEG 20.00 % FRP 33.33 % Whitethorn LLC 20.00 % Cactus II 15.00 % Saddlehorn 20.00 % Panola 15.00 % Mi Vida 50.00 % Ranch Westex 50.00 % Red Bluff Express 30.00 % Proportionate consolidation (2) Marcellus Interest systems 33.75 % Springfield system 50.10 % Full consolidation Chipeta (3) 75.00 % (1) Investments in non-controlled entities over which the Partnership exercises significant influence are accounted for under the equity method. “Equity investment throughput” refers to the Partnership’s share of average throughput for these investments. (2) The Partnership proportionately consolidates its associated share of the assets, liabilities, revenues and expenses attributable to these assets. (3) The 25% interest in Chipeta Processing LLC (“Chipeta”) held by a third-party member is reflected within noncontrolling interests in the consolidated financial statements, in addition to the noncontrolling interests noted below.

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Summary of Revenue from Contracts with Customers Table	The following table summarizes revenue from contracts with customers: Three Months Ended thousands 2019 2018 Revenue from customers Service revenues – fee based $ 579,974 $ 393,773 Service revenues – product based 19,379 23,423 Product sales 72,800 84,868 Total revenue from customers 672,153 502,064 Revenue from other than customers Net gains (losses) on commodity price swap agreements (667 ) (1,243 ) Other 397 233 Total revenues and other $ 671,883 $ 501,054
Contract Assets and Liabilities Activity Tables	The following table summarizes the current period activity related to contract liabilities from contracts with customers: thousands Balance at December 31, 2018 $ 145,624 Cash received or receivable, excluding revenues recognized during the period 15,213 Revenues recognized that were included in the contract liability balance at the beginning of the period (9,279 ) Balance at March 31, 2019 $ 151,558 Contract liabilities at March 31, 2019 Accrued liabilities $ 6,364 Other liabilities 145,194 Total contract liabilities from contracts with customers $ 151,558 The following table summarizes the current period activity related to contract assets from contracts with customers: thousands Balance at December 31, 2018 $ 47,621 Amounts transferred to Accounts receivable, net that were included in the contract assets balance at the beginning of the period (1,376 ) Additional estimated revenues recognized 3,810 Balance at March 31, 2019 $ 50,055 Contract assets at March 31, 2019 Other current assets $ 7,172 Other assets 42,883 Total contract assets from contracts with customers $ 50,055
Expected Revenue Recognition from Satisfaction of Performance Obligations Table	Therefore, the following table represents only a portion of expected future revenues from existing contracts as most future revenues from customers are dependent on future variable customer volumes and, in some cases, variable commodity prices for those volumes. thousands Remainder of 2019 $ 532,477 2020 862,428 2021 911,450 2022 976,136 2023 932,921 Thereafter 4,500,175 Total $ 8,715,587

Acquisitions and Divestitures (

Acquisitions and Divestitures (Tables)	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Impact to Historical Consolidated Statements of Income Tables	The following tables present the impact of AMA on Revenues and other, Equity income, net – affiliates and Net income (loss) as presented in the Partnership and WES Operating’s historical consolidated statements of operations: Three Months Ended March 31, 2018 thousands Partnership Historical (1) AMA Eliminations Combined Revenues and other $ 456,802 $ 51,664 $ (7,412 ) $ 501,054 Equity income, net – affiliates 20,424 9,805 — 30,229 Net income (loss) 150,488 30,522 — 181,010 Three Months Ended March 31, 2018 thousands WES Operating Historical (1) AMA Eliminations Combined Revenues and other $ 456,802 $ 51,664 $ (7,412 ) $ 501,054 Equity income, net – affiliates 20,424 9,805 — 30,229 Net income (loss) 152,348 30,522 — 182,870 (1) See Adjustments to previously issued financial statements within Note 1 .

Partnership Distributions (Tabl

Partnership Distributions (Tables)	3 Months Ended
	Mar. 31, 2019
Distributions Made to Members or Limited Partners [Abstract]
Cash Distributions Tables	For the 2018 periods noted below, WES Operating paid the following cash distributions to WES Operating’s common and general partner unitholders: thousands except per-unit amounts Quarters Ended Total Quarterly Total Quarterly Date of 2018 March 31 $ 0.935 $ 221,133 May 2018 June 30 0.950 225,691 August 2018 September 30 0.965 230,239 November 2018 December 31 0.980 234,787 February 2019 The Board of Directors of the general partner (the “Board of Directors”) declared the following cash distributions to the Partnership’s unitholders for the periods presented: thousands except per-unit amounts Quarters Ended Total Quarterly Total Quarterly Date of 2018 (1) March 31 $ 0.56875 $ 124,518 May 2018 June 30 0.58250 127,531 August 2018 September 30 0.59500 130,268 November 2018 December 31 0.60250 131,910 February 2019 2019 March 31 (2) $ 0.61000 $ 276,324 May 2019 (1) The 2018 distributions were declared and paid prior to the closing of the Merger. (2) The Board of Directors declared a cash distribution to the Partnership’s unitholders for the first quarter of 2019 of $0.61000 per unit, or $276.3 million in aggregate. The cash distribution is payable on May 14, 2019 , to unitholders of record at the close of business on May 1, 2019 .

Equity and Partners' Capital (T

Equity and Partners' Capital (Tables)	3 Months Ended
	Mar. 31, 2019
Partners' Capital Notes [Abstract]
Partnership Interests Table	In February 2019, the Partnership issued common units in connection with the closing of the Merger (see Note 1 ) as follows: Partnership common units outstanding prior to the Merger 218,937,797 WES Operating common units outstanding prior to the Merger 152,609,285 WES Operating Class C units outstanding prior to the Merger 14,681,388 Less: WES Operating common units owned by the Partnership (50,132,046 ) WES Operating common units subject to conversion into Partnership common units 117,158,627 Exchange ratio per unit 1.525 Partnership common units issued for WES Operating common units (1) 178,692,081 WES Operating common units issued as part of the AMA acquisition 45,760,201 Less: WES Operating common units retained by a subsidiary of Anadarko (6,375,284 ) WES Operating acquisition common units subject to conversion into Partnership common units 39,384,917 Conversion ratio per unit 1.4056 Partnership common units issued for WES Operating acquisition common units 55,360,984 Partnership common units outstanding at March 31, 2019 452,990,862 (1) Total Partnership units issued upon consummation of the Merger exceeds the calculation of such units using the exchange ratio due to the rounding convention reflected in the Merger Agreement. The following table summarizes WES Operating’s units issued during the three months ended March 31, 2019 : Common Units Class C Units General Partner Units Total Balance at December 31, 2018 152,609,285 14,372,665 2,583,068 169,565,018 PIK Class C units — 308,723 — 308,723 Conversion of Class C units (1) 14,681,388 (14,681,388 ) — — IDR and General partner unit conversion (1) 105,624,704 — (2,583,068 ) 103,041,636 Units issued as part of the AMA acquisition (1) 45,760,201 — — 45,760,201 Balance at March 31, 2019 318,675,578 — — 318,675,578 (1) See Note 1 for further details on the units issued and converted in connection with the closing of the Merger.
Calculation of Net Income (Loss) Per Unit Table	The following table illustrates the calculation of WES Operating’s net income (loss) per common unit: Three Months Ended thousands except per-unit amounts 2018 Net income (loss) attributable to Western Midstream Operating, LP $ 179,885 Pre-acquisition net (income) loss allocated to Anadarko (30,522 ) General partner interest in net (income) loss (83,439 ) Common and Class C limited partners’ interest in net income (loss) $ 65,924 Net income (loss) allocable to common units (1) $ 58,323 Net income (loss) allocable to Class C units (1) 7,601 Common and Class C limited partners’ interest in net income (loss) $ 65,924 Net income (loss) per unit Common units – basic and diluted (2) $ 0.38 Weighted-average units outstanding Common units – basic and diluted 152,602 Excluded due to anti-dilutive effect: Class C units (2) 13,380 (1) Adjusted to reflect amortization of the beneficial conversion feature. (2) The impact of Class C units would be anti-dilutive for the period presented.

Transactions with Affiliates (T

Transactions with Affiliates (Tables)	3 Months Ended
	Mar. 31, 2019
Related Party Transaction [Line Items]
Commodity Price Swap Agreements Tables	The tables below summarize the swap prices compared to the forward market prices: DJ Basin Complex per barrel except natural gas 2018 Swap Prices 2018 Market Prices (1) Ethane $ 18.41 $ 5.41 Propane 47.08 28.72 Isobutane 62.09 32.92 Normal butane 54.62 32.71 Natural gasoline 72.88 48.04 Condensate 76.47 49.36 Natural gas (per MMBtu) 5.96 2.21 MGR Assets per barrel except natural gas 2018 Swap Prices 2018 Market Prices (1) Ethane $ 23.11 $ 2.52 Propane 52.90 25.83 Isobutane 73.89 30.03 Normal butane 64.93 29.82 Natural gasoline 81.68 47.25 Condensate 81.68 56.76 Natural gas (per MMBtu) 4.87 2.21 (1) Represents the New York Mercantile Exchange forward strip price as of December 20, 2017, for the 2018 Market Prices, adjusted for product specification, location, basis and, in the case of NGLs, transportation and fractionation costs.
Related Party Transactions Tables	The following table summarizes material affiliate transactions included in the Partnership’s consolidated financial statements: Three Months Ended thousands 2019 2018 Revenues and other (1) $ 378,437 $ 285,176 Equity income, net – affiliates (1) 57,992 30,229 Cost of product (1) 56,172 34,819 Operation and maintenance (1) 39,141 23,001 General and administrative (2) 18,894 12,688 Operating expenses 114,207 70,508 Interest income (3) 4,225 4,225 Interest expense (4) 1,833 577 APCWH Note Payable borrowings (5) 11,000 106,565 Repayment of APCWH Note Payable (5) 439,595 — Distributions to Partnership unitholders (6) 102,654 98,000 Distributions to WES Operating unitholders (7) 2,543 1,850 Above-market component of swap agreements with Anadarko 7,407 14,282 (1) 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. (2) Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6 ) and amounts charged by Anadarko under the omnibus agreements of the Partnership and WES Operating. (3) Represents interest income recognized on the note receivable from Anadarko. (4) Includes amounts related to the APCWH Note Payable (see Note 1 and Note 10 ) . (5) See Note 1 . (6) Represents distributions paid to Anadarko under the partnership agreement of the Partnership (see Note 4 and Note 5 ). (7) Represents distributions paid to other subsidiaries of Anadarko under WES Operating’s partnership agreement (see Note 4 and Note 5 ).
WES Operating [Member]
Related Party Transaction [Line Items]
Related Party Transactions Tables	The following table summarizes affiliate transactions for WES Operating (which are included in the Partnership’s consolidated financial statements) to the extent the amounts differ from the Partnership’s consolidated financial statements: Three Months Ended thousands 2019 2018 General and administrative (1) $ 18,498 $ 12,479 Distributions to WES Operating unitholders (2) 164,902 124,164 (1) Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to WES Operating by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6 ) and amounts charged by Anadarko under the omnibus agreement of WES Operating. (2) 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 ).

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment Table	A summary of the historical cost of property, plant and equipment is as follows: thousands Estimated Useful Life March 31, December 31, Land n/a $ 8,858 $ 5,298 Gathering systems – pipelines 30 years 4,828,320 4,764,099 Gathering systems – compressors 15 years 1,809,009 1,712,939 Processing complexes and treating facilities 25 years 2,944,387 2,844,337 Transportation pipeline and equipment 6 to 45 years 172,637 172,558 Produced water disposal systems 20 years 667,106 629,946 Assets under construction n/a 603,234 604,265 Other 3 to 40 years 546,778 525,331 Total property, plant and equipment 11,580,329 11,258,773 Less accumulated depreciation 2,950,330 2,848,420 Net property, plant and equipment $ 8,629,999 $ 8,410,353

Equity Investments (Tables)

Equity Investments (Tables)	3 Months Ended
	Mar. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Equity Investments Table	The following table presents the equity investments activity for the three months ended March 31, 2019 : thousands Balance at December 31, 2018 Acquisitions Equity income, net Contributions (1) Distributions Distributions in excess of cumulative earnings (2) Balance at March 31, 2019 Fort Union $ 2,259 $ — $ (573 ) $ — $ — $ (237 ) $ 1,449 White Cliffs 43,020 — 3,225 1,845 (3,079 ) (935 ) 44,076 Rendezvous 37,841 — 121 — (607 ) (671 ) 36,684 Mont Belvieu JV 104,949 — 7,127 — (4,500 ) — 107,576 TEG 19,358 — 830 — (835 ) (316 ) 19,037 TEP 193,198 — 8,665 6,000 (9,865 ) — 197,998 FRP 176,436 — 7,125 — (6,480 ) — 177,081 Whitethorn LLC 161,858 — 21,860 3,228 (17,058 ) (5,213 ) 164,675 Cactus II 106,360 — — 17,791 — — 124,151 Saddlehorn 108,507 — 4,830 — (5,189 ) — 108,148 Panola 22,769 — 582 — (582 ) (228 ) 22,541 Mi Vida 64,632 — 1,685 — (2,451 ) — 63,866 Ranch Westex 50,901 — 2,027 — (3,087 ) (132 ) 49,709 Red Bluff Express — 92,546 488 7,679 (488 ) (60 ) 100,165 Total $ 1,092,088 $ 92,546 $ 57,992 $ 36,543 $ (54,221 ) $ (7,792 ) $ 1,217,156 (1) Includes capitalized interest of $1.5 million related to the construction of the pipeline owned by Cactus II. (2) 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.

Components of Working Capital (

Components of Working Capital (Tables)	3 Months Ended
	Mar. 31, 2019
Components Of Working Capital [Abstract]
Accounts Receivable, Net Table	A summary of accounts receivable, net is as follows: The Partnership WES Operating thousands March 31, December 31, March 31, December 31, Trade receivables, net $ 212,342 $ 221,119 $ 214,067 $ 221,328 Other receivables, net 81 45 81 45 Total accounts receivable, net $ 212,423 $ 221,164 $ 214,148 $ 221,373
Other Current Assets Table	A summary of other current assets is as follows: The Partnership WES Operating thousands March 31, December 31, March 31, December 31, NGLs inventory $ 6,861 $ 6,466 $ 6,861 $ 6,466 Imbalance receivables 5,800 9,035 5,800 9,035 Prepaid insurance 1,064 1,972 1,026 1,972 Contract assets 7,172 5,399 7,172 5,399 Other 2,575 4,184 2,575 3,309 Total other current assets $ 23,472 $ 27,056 $ 23,434 $ 26,181
Accrued Liabilities Table	A summary of accrued liabilities is as follows: The Partnership WES Operating thousands March 31, December 31, March 31, December 31, Accrued interest expense $ 55,831 $ 70,968 $ 55,831 $ 70,959 Short-term asset retirement obligations 23,033 25,938 23,033 25,938 Short-term remediation and reclamation obligations 863 863 863 863 Income taxes payable 861 384 861 384 Contract liabilities 6,364 16,235 6,364 16,235 Other (1) 54,490 14,760 54,315 13,495 Total accrued liabilities $ 141,442 $ 129,148 $ 141,267 $ 127,874 (1) Includes amounts related to WES Operating’s interest-rate swaps as of March 31, 2019 and December 31, 2018 (see Note 10 ). Includes lease liabilities related to the implementation of ASU 2016-02, Leases (Topic 842) as of March 31, 2019 (see Note 1 ).

Debt and Interest Expense (Tabl

Debt and Interest Expense (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Instruments [Abstract]
Debt Outstanding and Debt Activity Tables	The following table presents the outstanding debt: March 31, 2019 December 31, 2018 thousands Principal Carrying Value Fair Value (1) Principal Carrying Value Fair Value (1) Short-term debt WGP RCF $ — $ — $ — $ 28,000 $ 28,000 $ 28,000 364-day Facility 2,000,000 2,000,000 2,000,000 — — — Total short-term debt $ 2,000,000 $ 2,000,000 $ 2,000,000 $ 28,000 $ 28,000 $ 28,000 Long-term debt 5.375% Senior Notes due 2021 $ 500,000 $ 497,257 $ 518,755 $ 500,000 $ 496,959 $ 515,990 4.000% Senior Notes due 2022 670,000 669,138 680,293 670,000 669,078 662,109 3.950% Senior Notes due 2025 500,000 493,082 493,788 500,000 492,837 466,135 4.650% Senior Notes due 2026 500,000 495,830 507,034 500,000 495,710 483,994 4.500% Senior Notes due 2028 400,000 394,749 400,050 400,000 394,631 377,475 4.750% Senior Notes due 2028 400,000 395,928 407,849 400,000 395,841 384,370 5.450% Senior Notes due 2044 600,000 593,378 573,949 600,000 593,349 522,386 5.300% Senior Notes due 2048 700,000 686,696 664,278 700,000 686,648 605,327 5.500% Senior Notes due 2048 350,000 342,353 341,536 350,000 342,328 311,536 RCF 640,000 640,000 640,000 220,000 220,000 220,000 APCWH Note Payable — — — 427,493 427,493 427,493 Total long-term debt $ 5,260,000 $ 5,208,411 $ 5,227,532 $ 5,267,493 $ 5,214,874 $ 4,976,815 (1) Fair value is measured using the market approach and Level 2 inputs. Debt activity. The following table presents the debt activity for the three months ended March 31, 2019 : thousands Carrying Value Balance at December 31, 2018 $ 5,242,874 RCF borrowings 420,000 364-day Facility borrowings 2,000,000 APCWH Note Payable borrowings 11,000 Repayment of WGP RCF borrowings (28,000 ) Repayment of APCWH Note Payable (439,595 ) Other 2,132 Balance at March 31, 2019 $ 7,208,411
Interest-Rate Swap Table	The following interest-rate swaps were outstanding as of March 31, 2019 : Notional Principal Amount Reference Period Mandatory Termination Date Weighted-Average Interest Rate $375.0 million December 2019 - 2024 December 2019 2.662% $375.0 million December 2019 - 2029 December 2019 2.802% $375.0 million December 2019 - 2049 December 2019 2.885%
Interest Expense Table	The following table summarizes the amounts included in interest expense: Three Months Ended thousands 2019 2018 Third parties Long-term and short-term debt $ (67,096 ) $ (41,536 ) Amortization of debt issuance costs and commitment fees (3,152 ) (2,864 ) Capitalized interest 6,205 6,962 Total interest expense – third parties (64,043 ) (37,438 ) Affiliates APCWH Note Payable (1,833 ) (577 ) Total interest expense – affiliates (1,833 ) (577 ) Interest expense $ (65,876 ) $ (38,015 )

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Summary of Leases Table	The following table summarizes other information related to operating leases: thousands except lease term and discount rate March 31, 2019 Lease assets Other assets $ 10,002 Lease liabilities Accrued liabilities 7,560 Other liabilities 3,343 Weighted-average remaining lease term (years) 4 Weighted-average discount rate 4.1 %
Operating Leases Liability Maturity Tables	The following table reconciles the undiscounted cash flows to the operating lease liabilities at March 31, 2019 , that may be assigned or otherwise charged to the Partnership pursuant to the reimbursement provisions of the omnibus agreement: thousands Remainder of 2019 $ 5,588 2020 2,215 2021 612 2022 618 2023 625 Thereafter 1,658 Total lease payments 11,316 Less portion representing imputed interest 413 Total lease liabilities $ 10,903 The amounts in the table below represent contractual operating lease commitments at December 31, 2018 , that may be assigned or otherwise charged to the Partnership pursuant to the reimbursement provisions of the omnibus agreement: thousands 2019 $ 8,711 2020 2,236 2021 460 2022 467 2023 473 Thereafter 1,547 Total lease payments $ 13,894

Description of Business and B_4

Description of Business and Basis of Presentation - Assets and Investments Table (Details)	Mar. 31, 2019unit
Owned and Operated [Member] | Gathering Systems [Member]
Assets [Line Items]
Assets, number of units	17	[1]
Owned and Operated [Member] | Treating Facilities [Member]
Assets [Line Items]
Assets, number of units	35
Owned and Operated [Member] | Natural Gas Processing Plants/Trains [Member]
Assets [Line Items]
Assets, number of units	24
Owned and Operated [Member] | Natural Gas Liquids Pipelines [Member]
Assets [Line Items]
Assets, number of units	2
Owned and Operated [Member] | Natural Gas Pipelines [Member]
Assets [Line Items]
Assets, number of units	5
Owned and Operated [Member] | Oil Pipelines [Member]
Assets [Line Items]
Assets, number of units	3
Operated Interests [Member] | Gathering Systems [Member]
Assets [Line Items]
Assets, number of units	2	[1]
Operated Interests [Member] | Treating Facilities [Member]
Assets [Line Items]
Assets, number of units	3
Operated Interests [Member] | Natural Gas Processing Plants/Trains [Member]
Assets [Line Items]
Assets, number of units	3
Operated Interests [Member] | Oil Pipelines [Member]
Assets [Line Items]
Assets, number of units	1
Non-Operated Interests [Member] | Gathering Systems [Member]
Assets [Line Items]
Assets, number of units	3	[1]
Equity Interests [Member] | Gathering Systems [Member]
Assets [Line Items]
Assets, number of units	2	[1]
Equity Interests [Member] | Treating Facilities [Member]
Assets [Line Items]
Assets, number of units	3
Equity Interests [Member] | Natural Gas Processing Plants/Trains [Member]
Assets [Line Items]
Assets, number of units	5
Equity Interests [Member] | Natural Gas Liquids Pipelines [Member]
Assets [Line Items]
Assets, number of units	4
Equity Interests [Member] | Natural Gas Pipelines [Member]
Assets [Line Items]
Assets, number of units	1
Equity Interests [Member] | Oil Pipelines [Member]
Assets [Line Items]
Assets, number of units	3
[1]	Includes the DBM water systems.

Description of Business and B_5

Description of Business and Basis of Presentation - Ownership Interests and Method of Consolidation Table (Details)	3 Months Ended
	Mar. 31, 2019
Chipeta [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Ownership interest by noncontrolling interest owner	25.00%
Equity Investments [Member] | Fort Union [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	14.81%	[1]
Equity Investments [Member] | White Cliffs [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	10.00%	[1]
Equity Investments [Member] | Rendezvous [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	22.00%	[1]
Equity Investments [Member] | Mont Belvieu JV [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	25.00%	[1]
Equity Investments [Member] | Texas Express Pipeline [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	20.00%	[1]
Equity Investments [Member] | Texas Express Gathering [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	20.00%	[1]
Equity Investments [Member] | Front Range Pipeline [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	33.33%	[1]
Equity Investments [Member] | Whitethorn LLC [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	20.00%	[1]
Equity Investments [Member] | Cactus II [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	15.00%	[1]
Equity Investments [Member] | Saddlehorn [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	20.00%	[1]
Equity Investments [Member] | Panola [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	15.00%	[1]
Equity Investments [Member] | Mi Vida [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	50.00%	[1]
Equity Investments [Member] | Ranch Westex [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	50.00%	[1]
Equity Investments [Member] | Red Bluff Express [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Equity investment ownership percentage	30.00%	[1]
Proportionate Consolidation [Member] | Marcellus Interest Systems [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Percentage ownership interest	33.75%	[2]
Proportionate Consolidation [Member] | Springfield System [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Percentage ownership interest	50.10%	[2]
Full Consolidation [Member] | Chipeta [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Percentage ownership interest	75.00%	[3]
[1]	Investments in non-controlled entities over which the Partnership exercises significant influence are accounted for under the equity method. “Equity investment throughput” refers to the Partnership’s share of average throughput for these investments.
[2]	The Partnership proportionately consolidates its associated share of the assets, liabilities, revenues and expenses attributable to these assets.
[3]	The 25% interest in Chipeta Processing LLC (“Chipeta”) held by a third-party member is reflected within noncontrolling interests in the consolidated financial statements, in addition to the noncontrolling interests noted below.

Description of Business and B_6

Description of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands		Feb. 28, 2019	Mar. 31, 2019		Jun. 30, 2018	Mar. 31, 2018		Dec. 31, 2018
Acquisitions			$ 92,546
Common units outstanding			452,990,862					218,937,797
Conversion ratio per unit		1.525
Revenues and other			$ 671,883			$ 501,054	[1]
Cost of product	[2]		$ 114,063			94,318	[1]
Prior Period Adjustment [Member]
Cost of product						19,600
Prior Period Adjustment [Member] | Service Revenues - Fee Based [Member]
Revenues and other						14,300
Prior Period Adjustment [Member] | Product Sales [Member]
Revenues and other						5,300
Chipeta [Member]
Ownership interest by noncontrolling interest owner			25.00%
WES Operating [Member]
Ownership interest by noncontrolling interest owner			2.00%
Anadarko Midstream Assets [Member]
Conversion ratio per unit		1.4056
Revenues and other						51,664
Affiliates [Member]
Revenues and other	[3]		$ 378,437			285,176	[1]
Cost of product	[3]		56,172			34,819
Affiliates [Member] | Service Revenues - Fee Based [Member]
Revenues and other			326,642			222,038	[1]
Affiliates [Member] | Product Sales [Member]
Revenues and other			50,443			62,507	[1]
Affiliates [Member] | Product Sales [Member] | Kitty Draw and Third Creek Gathering Systems [Member]
Revenues and other			$ 5,500		$ (10,900)
WES Operating [Member]
Units issued			308,723
General partner units owned			0					2,583,068
Conversion of units	[4]		0
Revenues and other			$ 671,883			501,054	[1]
Cost of product	[5]		$ 114,063			94,318	[1]
WES Operating [Member] | Anadarko Midstream Assets [Member]
Units issued	[4]		45,760,201
Revenues and other						51,664
WES Operating [Member] | Anadarko [Member] | Anadarko Midstream Assets [Member]
Cash payment for acquisition		$ 1,814,000
Acquisitions		$ 193,900
WES Operating [Member] | Affiliates [Member]
Revenues and other			$ 378,437			285,176	[1]
Cost of product	[3]		56,172			34,819
WES Operating [Member] | Affiliates [Member] | Service Revenues - Fee Based [Member]
Revenues and other			326,642			222,038	[1]
WES Operating [Member] | Affiliates [Member] | Product Sales [Member]
Revenues and other			$ 50,443			$ 62,507	[1]
WES Operating [Member] | Common Units [Member]
Conversion of units		105,624,704	14,681,388	[4]
Common units outstanding		152,609,285
WES Operating [Member] | Common Units [Member] | Anadarko Midstream Assets [Member]
Units issued		45,760,201	45,760,201	[4]
WES Operating [Member] | Common Units [Member] | Anadarko [Member] | Anadarko Midstream Assets [Member]
Units issued		45,760,201
WES Operating [Member] | Class C Units [Member]
Units issued			308,723
Class C units, common units issued upon conversion		1
Conversion of units	[4]		(14,681,388)
Common units outstanding		14,681,388
Anadarko [Member] | WES Operating [Member]
Ownership interest			2.00%
Anadarko [Member] | Common Units [Member] | WES Operating [Member]
Common units outstanding			6,375,284
Anadarko [Member] | Common Units [Member] | Anadarko Midstream Assets [Member] | WES Operating [Member]
Common units outstanding		6,375,284
WES [Member] | WES Operating [Member]
Ownership interest			98.00%
General partner units owned		2,583,068
WES [Member] | Common Units [Member]
Conversion of units	[6]	178,692,081
Common units outstanding		218,937,797	452,990,862
WES [Member] | Common Units [Member] | WES Operating [Member]
Common units outstanding		50,132,046
WES [Member] | Common Units [Member] | Anadarko Midstream Assets [Member]
Conversion of units		55,360,984
[1]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[2]	Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.9 million and $12.7 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.
[3]	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.
[4]	See Note 1 for further details on the units issued and converted in connection with the closing of the Merger.
[5]	Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.5 million and $12.5 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.
[6]	Total Partnership units issued upon consummation of the Merger exceeds the calculation of such units using the exchange ratio due to the rounding convention reflected in the Merger Agreement.

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Revenue From Contracts With Customers Table (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue from customers	$ 672,153	$ 502,064
Total revenues and other	671,883	501,054	[1]
Service Revenues - Fee Based [Member]
Disaggregation of Revenue [Line Items]
Revenue from customers	579,974	393,773
Service Revenues - Product Based [Member]
Disaggregation of Revenue [Line Items]
Revenue from customers	19,379	23,423
Product Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue from customers	72,800	84,868
Commodity Price Swap Agreement [Member]
Disaggregation of Revenue [Line Items]
Revenue from other than customers	(667)	(1,243)
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from other than customers	$ 397	$ 233
[1]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Contract Assets Table (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Change in Contracts with Customer, Asset [Roll Forward]
Balance at December 31, 2018	$ 47,621
Amounts transferred to Accounts receivable, net that were included in the contract assets balance at the beginning of the period	(1,376)
Additional estimated revenues recognized	3,810
Balance at March 31, 2019	50,055
Contract assets at March 31, 2019
Other current assets		$ 7,172	$ 5,399
Other assets		42,883
Total contract assets from contracts with customers	$ 47,621	$ 50,055	$ 47,621

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Contract Liabilities Table (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Change in Contracts with Customer, Liability [Roll Forward]
Balance at December 31, 2018	$ 145,624
Cash received or receivable, excluding revenues recognized during the period	15,213
Revenues recognized that were included in the contract liability balance at the beginning of the period	(9,279)
Balance at March 31, 2019	151,558
Contract liabilities at March 31, 2019
Accrued liabilities		$ 6,364	$ 16,235
Other liabilities		145,194
Total contract liabilities from contracts with customers	$ 145,624	$ 151,558	$ 145,624

Revenue from Contracts with C_6

Revenue from Contracts with Customers - Expected Revenues Table (Details) $ in Thousands	Mar. 31, 2019USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 532,477
Performance obligation expected to be satisfied, expected timing	9 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 862,428
Performance obligation expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 911,450
Performance obligation expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 976,136
Performance obligation expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 932,921
Performance obligation expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 8,715,587
Performance obligation expected to be satisfied, expected timing

Revenue from Contracts with C_7

Revenue from Contracts with Customers - Additional Information (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Revenue from Contracts with Customer [Line Items]
Accounts receivable, net	[1]	$ 212,423	$ 221,164	[2]
Customers [Member]
Revenue from Contracts with Customer [Line Items]
Accounts receivable, net		$ 315,300	$ 214,300
[1]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $68.5 million and $72.6 million as of March 31, 2019, and December 31, 2018, respectively.
[2]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.

Acquisitions and Divestitures -

Acquisitions and Divestitures - Impact to Historical Consolidated Statements of Operations Table (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other		$ 671,883	$ 501,054	[1]
Equity income, net – affiliates	[2]	57,992	30,229	[1]
Net income (loss)		211,979	181,010	[1]
Anadarko Midstream Assets [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other			51,664
Equity income, net – affiliates			9,805
Net income (loss)			30,522
Anadarko Midstream Assets [Member] | Eliminations [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other			(7,412)
Equity income, net – affiliates			0
Net income (loss)			0
Historical financial data [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other	[3]		456,802
Equity income, net – affiliates	[3]		20,424
Net income (loss)	[3]		150,488
WES Operating [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other		671,883	501,054	[1]
Equity income, net – affiliates		57,992	30,229	[1]
Net income (loss)		$ 214,450	182,870	[1]
WES Operating [Member] | Anadarko Midstream Assets [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other			51,664
Equity income, net – affiliates			9,805
Net income (loss)			30,522
WES Operating [Member] | Anadarko Midstream Assets [Member] | Eliminations [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other			(7,412)
Equity income, net – affiliates			0
Net income (loss)			0
WES Operating [Member] | Historical financial data [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other	[3]		456,802
Equity income, net – affiliates	[3]		20,424
Net income (loss)	[3]		$ 152,348
[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]	See Adjustments to previously issued financial statements within Note 1.

Acquisitions and Divestitures_2

Acquisitions and Divestitures - Additional Information (Details) $ in Thousands	Feb. 28, 2019	Jan. 18, 2019USD ($)	Mar. 31, 2019USD ($)MBbls / dMcf / dmibbl
Property, Plant and Equipment [Line Items]
Acquisition, net investment | $			$ 92,546
Wattenberg Processing Plant [Member] | Cryogenic Train [Member]
Property, Plant and Equipment [Line Items]
Gas processing capacity			190,000
Wattenberg Processing Plant [Member] | Refrigeration Train [Member]
Property, Plant and Equipment [Line Items]
Gas processing capacity			100,000
DJ Basin Oil System [Member]
Property, Plant and Equipment [Line Items]
Oil processing capacity | MBbls / d			155
DJ Basin Oil System [Member] | Pipelines [Member]
Property, Plant and Equipment [Line Items]
Pipeline miles | mi			12
DJ Basin Oil System [Member] | Storage Tank [Member]
Property, Plant and Equipment [Line Items]
Storage capacity - barrels | bbl			500,000
DBM Oil System [Member] | Pipelines [Member]
Property, Plant and Equipment [Line Items]
Pipeline miles | mi			14
DBM Oil System [Member] | Storage Tank [Member]
Property, Plant and Equipment [Line Items]
Storage capacity - barrels | bbl			30,000
DBM Oil System [Member] | Central Production Facilities [Member]
Property, Plant and Equipment [Line Items]
Oil processing capacity | MBbls / d			71
DBM Oil System [Member] | Regional Oil Treating Facilities [Member]
Property, Plant and Equipment [Line Items]
Oil processing capacity | MBbls / d			120
APC Water Systems [Member]
Property, Plant and Equipment [Line Items]
Produced water processing capacity | MBbls / d			565
Saddlehorn [Member]
Property, Plant and Equipment [Line Items]
Ownership percentage acquired	20.00%
Saddlehorn [Member] | Storage Tank [Member]
Property, Plant and Equipment [Line Items]
Storage capacity - barrels | bbl			300,000
Panola [Member]
Property, Plant and Equipment [Line Items]
Ownership percentage acquired	15.00%
Panola [Member] | Pipelines [Member]
Property, Plant and Equipment [Line Items]
Pipeline miles | mi			248
Mi Vida [Member]
Property, Plant and Equipment [Line Items]
Gas processing capacity			200,000
Ownership percentage acquired	50.00%
Ranch Westex [Member]
Property, Plant and Equipment [Line Items]
Ownership percentage acquired	50.00%
Ranch Westex [Member] | Cryogenic Train [Member]
Property, Plant and Equipment [Line Items]
Gas processing capacity			100,000
Ranch Westex [Member] | Refrigeration Train [Member]
Property, Plant and Equipment [Line Items]
Gas processing capacity			25,000
Red Bluff Express [Member]
Property, Plant and Equipment [Line Items]
Ownership percentage acquired		30.00%
Acquisition, net investment | $		$ 92,500

Partnership Distributions - Cas

Partnership Distributions - Cash Distributions Tables (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018
Distribution Made to Limited Partner [Line Items]
Total quarterly distribution per unit	$ 0.61000	[1]	$ 0.60250	[2]	$ 0.59500	[2]	$ 0.58250	[2]	$ 0.56875	[2]
Total quarterly cash distribution	$ 276,324	[1]	$ 131,910	[2]	$ 130,268	[2]	$ 127,531	[2]	$ 124,518	[2]
WES Operating [Member]
Distribution Made to Limited Partner [Line Items]
Total quarterly distribution per unit			$ 0.980		$ 0.965		$ 0.950		$ 0.935
Total quarterly cash distribution	$ 283,300		$ 234,787		$ 230,239		$ 225,691		$ 221,133
[1]	The Board of Directors declared a cash distribution to the Partnership’s unitholders for the first quarter of 2019 of $0.61000 per unit, or $276.3 million in aggregate. The cash distribution is payable on May 14, 2019, to unitholders of record at the close of business on May 1, 2019.
[2]	The 2018 distributions were declared and paid prior to the closing of the Merger.

Partnership Distributions - Add

Partnership Distributions - Additional Information (Details) - USD ($) $ in Thousands	Feb. 28, 2019	Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018
Distribution Made to Limited Partner [Line Items]
Partnership agreement day requirement of distribution of available cash		55 days
Common units outstanding		452,990,862		218,937,797
Total quarterly cash distribution		$ 276,324	[1]	$ 131,910	[2]	$ 130,268	[2]	$ 127,531	[2]	$ 124,518	[2]
WES Operating [Member]
Distribution Made to Limited Partner [Line Items]
Total quarterly cash distribution		$ 283,300		$ 234,787		$ 230,239		$ 225,691		$ 221,133
Distribution sharing percentage	1.50%
Incentive distributions percentage	48.00%
WES Operating [Member] | Common Units [Member]
Distribution Made to Limited Partner [Line Items]
Common units outstanding	152,609,285
WES Operating [Member] | Class C Units [Member]
Distribution Made to Limited Partner [Line Items]
Common units outstanding	14,681,388
Class C units, discount rate percentage on distribution	6.00%
Class C units, common units issued upon conversion	1
WES Operating [Member] | Anadarko [Member] | Common Units [Member]
Distribution Made to Limited Partner [Line Items]
Common units outstanding		6,375,284
[1]	The Board of Directors declared a cash distribution to the Partnership’s unitholders for the first quarter of 2019 of $0.61000 per unit, or $276.3 million in aggregate. The cash distribution is payable on May 14, 2019, to unitholders of record at the close of business on May 1, 2019.
[2]	The 2018 distributions were declared and paid prior to the closing of the Merger.

Equity and Partners' Capital -

Equity and Partners' Capital - WES Units Table (Details) - shares		Feb. 28, 2019	Mar. 31, 2019		Dec. 31, 2018
Capital Unit [Line Items]
Limited partner units			452,990,862		218,937,797
Conversion ratio per unit		1.525
Anadarko Midstream Assets [Member]
Capital Unit [Line Items]
Conversion ratio per unit		1.4056
WES Operating [Member]
Capital Unit [Line Items]
Units issued			308,723
Conversion of units	[1]		0
WES Operating [Member] | Anadarko Midstream Assets [Member]
Capital Unit [Line Items]
Units issued	[1]		45,760,201
Common Units [Member] | WES [Member]
Capital Unit [Line Items]
Limited partner units		218,937,797	452,990,862
Conversion of units	[2]	178,692,081
Common Units [Member] | WES [Member] | Anadarko Midstream Assets [Member]
Capital Unit [Line Items]
Conversion of units		55,360,984
Common Units [Member] | WES Operating [Member]
Capital Unit [Line Items]
Limited partner units		152,609,285
Units subject to conversion		117,158,627
Conversion of units		105,624,704	14,681,388	[1]
Common Units [Member] | WES Operating [Member] | Anadarko Midstream Assets [Member]
Capital Unit [Line Items]
Units issued		45,760,201	45,760,201	[1]
Units subject to conversion		39,384,917
Class C Units [Member] | WES Operating [Member]
Capital Unit [Line Items]
Limited partner units		14,681,388
Units issued			308,723
Conversion of units	[1]		(14,681,388)
WES Operating [Member] | Common Units [Member] | WES [Member]
Capital Unit [Line Items]
Limited partner units		50,132,046
WES Operating [Member] | Common Units [Member] | Anadarko [Member]
Capital Unit [Line Items]
Limited partner units			6,375,284
WES Operating [Member] | Common Units [Member] | Anadarko [Member] | Anadarko Midstream Assets [Member]
Capital Unit [Line Items]
Limited partner units		6,375,284
[1]	See Note 1 for further details on the units issued and converted in connection with the closing of the Merger.
[2]	Total Partnership units issued upon consummation of the Merger exceeds the calculation of such units using the exchange ratio due to the rounding convention reflected in the Merger Agreement.

Equity and Partners' Capital _2

Equity and Partners' Capital - WES Operating Interests Table (Details) - WES Operating [Member] - shares		Feb. 28, 2019	Mar. 31, 2019
Change In Units [Roll Forward]
Balance			169,565,018
Units issued			308,723
Conversion of Class C units	[1]		0
IDR and General partner unit conversion	[1]		103,041,636
Balance			318,675,578
Anadarko Midstream Assets [Member]
Change In Units [Roll Forward]
Units issued	[1]		45,760,201
Common Units [Member]
Change In Units [Roll Forward]
Balance			152,609,285
Conversion of Class C units		105,624,704	14,681,388	[1]
IDR and General partner unit conversion	[1]		105,624,704
Balance			318,675,578
Common Units [Member] | Anadarko Midstream Assets [Member]
Change In Units [Roll Forward]
Units issued		45,760,201	45,760,201	[1]
Class C Units [Member]
Change In Units [Roll Forward]
Balance			14,372,665
Units issued			308,723
Conversion of Class C units	[1]		(14,681,388)
Balance			0
General Partner [Member]
Change In Units [Roll Forward]
Balance			2,583,068
IDR and General partner unit conversion	[1]		(2,583,068)
Balance			0
[1]	See Note 1 for further details on the units issued and converted in connection with the closing of the Merger.

Equity and Partners' Capital _3

Equity and Partners' Capital - Calculation of WES Operating Net Income (Loss) Per Unit Table (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Earnings Per Unit [Line Items]
Net income (loss) attributable to Western Midstream Operating, LP		$ 118,660	$ 131,527	[1]
Pre-acquisition net (income) loss allocated to Anadarko		(29,116)	(30,522)	[1]
Limited partners' interest in net income (loss)		89,544	101,005	[1]
WES Operating [Member]
Earnings Per Unit [Line Items]
Net income (loss) attributable to Western Midstream Operating, LP		212,596	179,885	[1]
Pre-acquisition net (income) loss allocated to Anadarko		(29,116)	(30,522)	[1]
General partner interest in net (income) loss	[2]	$ 0	(83,439)	[1]
WES Operating [Member] | Common and Class C Units [Member]
Earnings Per Unit [Line Items]
Limited partners' interest in net income (loss)			65,924
WES Operating [Member] | Common Units [Member]
Earnings Per Unit [Line Items]
Limited partners' interest in net income (loss)	[3]		$ 58,323
Net income (loss) per common unit - basic and diluted	[1],[2],[4]		$ 0.38
Weighted-average common units outstanding - basic and diluted			152,602
WES Operating [Member] | Class C Units [Member]
Earnings Per Unit [Line Items]
Limited partners' interest in net income (loss)	[3]		$ 7,601
Anti-dilutive units excluded from computation of earnings per unit	[4]		13,380
[1]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[2]	See Note 5 for the calculation of net income (loss) per common unit.
[3]	Adjusted to reflect amortization of the beneficial conversion feature.
[4]	The impact of Class C units would be anti-dilutive for the period presented.

Equity and Partners' Capital _4

Equity and Partners' Capital - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Nov. 30, 2014	Mar. 31, 2019	Dec. 31, 2014	Feb. 28, 2019	Dec. 31, 2018
Schedule of Investments [Line Items]
Limited partner units		452,990,862			218,937,797
Class C Units [Member]
Schedule of Investments [Line Items]
Beneficial conversion feature			$ 34.8
WES [Member] | Public [Member]
Schedule of Investments [Line Items]
Limited partner units		201,793,245
Ownership interest		44.50%
WES [Member] | WES Operating [Member]
Schedule of Investments [Line Items]
Ownership interest		98.00%
Anadarko [Member] | WES [Member]
Schedule of Investments [Line Items]
Limited partner units		251,197,617
Ownership interest		55.50%
Anadarko [Member] | WES Operating [Member]
Schedule of Investments [Line Items]
Ownership interest		2.00%
WES Operating [Member]
Schedule of Investments [Line Items]
Units issued		308,723
WES Operating [Member] | Class C Units [Member]
Schedule of Investments [Line Items]
Limited partner units				14,681,388
Units issued		308,723
Class C units, common units issued upon conversion				1
WES Operating [Member] | Class C Units [Member] | Other Subsidiaries of Anadarko [Member]
Schedule of Investments [Line Items]
Units issued	10,913,853

Transactions with Affiliates -

Transactions with Affiliates - Commodity Price Swap Agreements Tables (Details) - Year 2018 [Member]		Dec. 31, 2018$ / MMBTU$ / bbl	Dec. 20, 2017$ / MMBTU$ / bbl
DJ Basin Complex [Member] | Ethane [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price		18.41
Commodity market price	[1]		5.41
DJ Basin Complex [Member] | Propane [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price		47.08
Commodity market price	[1]		28.72
DJ Basin Complex [Member] | Isobutane [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price		62.09
Commodity market price	[1]		32.92
DJ Basin Complex [Member] | Normal Butane [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price		54.62
Commodity market price	[1]		32.71
DJ Basin Complex [Member] | Natural Gasoline [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price		72.88
Commodity market price	[1]		48.04
DJ Basin Complex [Member] | Condensate [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price		76.47
Commodity market price	[1]		49.36
DJ Basin Complex [Member] | Natural Gas (per MMBtu) [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price | $ / MMBTU		5.96
Commodity market price | $ / MMBTU	[1]		2.21
MGR Assets [Member] | Ethane [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price		23.11
Commodity market price	[1]		2.52
MGR Assets [Member] | Propane [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price		52.90
Commodity market price	[1]		25.83
MGR Assets [Member] | Isobutane [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price		73.89
Commodity market price	[1]		30.03
MGR Assets [Member] | Normal Butane [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price		64.93
Commodity market price	[1]		29.82
MGR Assets [Member] | Natural Gasoline [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price		81.68
Commodity market price	[1]		47.25
MGR Assets [Member] | Condensate [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price		81.68
Commodity market price	[1]		56.76
MGR Assets [Member] | Natural Gas (per MMBtu) [Member]
Commodity Price Risk Swap [Line Items]
Commodity swap fixed price | $ / MMBTU		4.87
Commodity market price | $ / MMBTU	[1]		2.21
[1]	Represents the New York Mercantile Exchange forward strip price as of December 20, 2017, for the 2018 Market Prices, adjusted for product specification, location, basis and, in the case of NGLs, transportation and fractionation costs.

Transactions with Affiliates _2

Transactions with Affiliates - Summary of Affiliate Transactions Tables (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Related Party Transaction [Line Items]
Revenues and other		$ 671,883	$ 501,054	[1]
Equity income, net – affiliates	[2]	57,992	30,229	[1]
Cost of product	[3]	114,063	94,318	[1]
Operation and maintenance	[3]	142,829	96,795	[1]
General and administrative	[3]	22,844	15,829	[1]
Operating expenses		410,357	306,532	[1]
Interest income	[4]	4,225	4,225	[1]
Interest expense	[5]	65,876	38,015	[1]
Distributions to unitholders	[6]	131,910	120,140	[1]
Above-market component of swap agreements with Anadarko	[6]	7,407	14,282	[1]
WES Operating [Member]
Related Party Transaction [Line Items]
Revenues and other		671,883	501,054	[1]
Equity income, net – affiliates		57,992	30,229	[1]
Cost of product	[7]	114,063	94,318	[1]
Operation and maintenance	[7]	142,829	96,795	[1]
General and administrative	[7]	20,560	14,997	[1]
Operating expenses		408,073	305,700	[1]
Interest income	[4]	4,225	4,225	[1]
Interest expense	[8]	65,631	36,952	[1]
Distributions to unitholders	[9]	263,358	216,586	[1]
Above-market component of swap agreements with Anadarko	[9]	7,407	14,282	[1]
Affiliates [Member]
Related Party Transaction [Line Items]
Revenues and other	[2]	378,437	285,176	[1]
Cost of product	[2]	56,172	34,819
Operation and maintenance	[2]	39,141	23,001
General and administrative	[10]	18,894	12,688
Operating expenses		114,207	70,508
Interest expense	[11]	1,833	577
APCWH Note Payable borrowings	[12]	11,000	106,565
Repayment of APCWH Note Payable	[12]	439,595	0
Distributions to unitholders	[13]	102,654	98,000
Affiliates [Member] | WES Operating [Member]
Related Party Transaction [Line Items]
Revenues and other		378,437	285,176	[1]
Cost of product	[2]	56,172	34,819
Operation and maintenance	[2]	39,141	23,001
General and administrative	[14]	18,498	12,479
Interest expense	[11]	1,833	577
Distributions to unitholders	[15]	164,902	124,164
WES Operating [Member] | Affiliates [Member]
Related Party Transaction [Line Items]
Distributions to unitholders	[16]	$ 2,543	$ 1,850
[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]	Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.9 million and $12.7 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.
[4]	Represents interest income recognized on the note receivable from Anadarko.
[5]	Includes affiliate (as defined in Note 1) amounts of $1.8 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively. See Note 1 and Note 10.
[6]	See Note 6.
[7]	Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.5 million and $12.5 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.
[8]	Includes affiliate (as defined in Note 1) amounts of $1.8 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively. See Note 1 and Note 10.
[9]	See Note 6.
[10]	Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to the Partnership by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6) and amounts charged by Anadarko under the omnibus agreements of the Partnership and WES Operating.
[11]	Includes amounts related to the APCWH Note Payable (see Note 1 and Note 10).
[12]	See Note 1.
[13]	Represents distributions paid to Anadarko under the partnership agreement of the Partnership (see Note 4 and Note 5).
[14]	Represents general and administrative expense incurred on and subsequent to the date of the acquisition of Partnership assets, as well as a management services fee for expenses incurred by Anadarko for periods prior to the acquisition of such assets. These amounts include equity-based compensation expense allocated to WES Operating by Anadarko (see LTIPs and Anadarko Incentive Plan within this Note 6) and amounts charged by Anadarko under the omnibus agreement of WES Operating.
[15]	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).
[16]	Represents distributions paid to other subsidiaries of Anadarko under WES Operating’s partnership agreement (see Note 4 and Note 5).

Transactions with Affiliates _3

Transactions with Affiliates - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended
	May 31, 2008	Mar. 31, 2019		Mar. 31, 2018		Dec. 31, 2018
Related Party Transaction [Line Items]
Note receivable - Anadarko		$ 260,000,000				$ 260,000,000	[1]
Above-market component of swap agreements with Anadarko		$ 7,407,000	[2]	$ 14,282,000	[1],[3]
Long-Term Incentive Plans [Member]
Related Party Transaction [Line Items]
Units vesting period		3 years
Natural Gas [Member] | Gathering, Treating, Transportation and Disposal [Member]
Related Party Transaction [Line Items]
Affiliate throughput percent		6.00%		7.00%
Natural Gas [Member] | Processing [Member]
Related Party Transaction [Line Items]
Affiliate throughput percent		41.00%		40.00%
Crude Oil, NGLs and Produced Water [Member] | Gathering, Treating, Transportation and Disposal [Member]
Related Party Transaction [Line Items]
Affiliate throughput percent		83.00%		79.00%
Commodity Price Swap Agreement [Member]
Related Party Transaction [Line Items]
Net gains (losses) on commodity price swap agreements		$ (667,000)		$ (1,243,000)
Affiliates [Member] | Commodity Price Swap Agreement [Member]
Related Party Transaction [Line Items]
Net gains (losses) on commodity price swap agreements		(667,000)		(1,243,000)
Affiliates [Member] | Level 2 Inputs [Member] | Valuation, Market Approach [Member]
Related Party Transaction [Line Items]
Fair value of the note receivable		$ 303,900,000				279,600,000
Independent Director [Member] | Long-Term Incentive Plans [Member]
Related Party Transaction [Line Items]
Units vesting period		1 year
WES Operating [Member]
Related Party Transaction [Line Items]
Note receivable - Anadarko		$ 260,000,000				$ 260,000,000	[1]
Above-market component of swap agreements with Anadarko		$ 7,407,000	[4]	$ 14,282,000	[1],[5]
WES Operating [Member] | Affiliates [Member]
Related Party Transaction [Line Items]
Note receivable - Anadarko	$ 260,000,000
Note receivable, due date	May 14, 2038
Fixed annual rate for note receivable bearing interest	6.50%
[1]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[2]	See Note 6.
[3]	See Note 6.
[4]	See Note 6.
[5]	See Note 6.

Property, Plant and Equipment -

Property, Plant and Equipment - Historical Cost Table (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 11,580,329	$ 11,258,773	[1]
Less accumulated depreciation	2,950,330	2,848,420	[1]
Net property, plant and equipment	8,629,999	8,410,353	[1]
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	8,858	5,298
Gathering Systems – Pipelines [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 4,828,320	4,764,099
Estimated useful life	30 years
Gathering Systems – Compressors [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,809,009	1,712,939
Estimated useful life	15 years
Processing Complexes And Treating Facilities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 2,944,387	2,844,337
Estimated useful life	25 years
Transportation Pipeline And Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 172,637	172,558
Transportation Pipeline And Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	6 years
Transportation Pipeline And Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	45 years
Produced Water Disposal Systems [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 667,106	629,946
Estimated useful life	20 years
Assets Under Construction [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 603,234	604,265
Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 546,778	$ 525,331
Other [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Other [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	40 years
[1]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Details) - USD ($)	3 Months Ended			12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	[1]	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Impairments	$ 390,000	$ 200,000		$ 230,600,000
Third Creek Gathering System [Member]
Property, Plant and Equipment [Line Items]
Impairments				125,900,000
Third Creek Gathering System [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Market Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated salvage value				1,800,000
Kitty Draw Gathering System [Member]
Property, Plant and Equipment [Line Items]
Impairments				8,100,000
Kitty Draw Gathering System [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Market Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated salvage value				0
Hilight System [Member]
Property, Plant and Equipment [Line Items]
Impairments				38,700,000
Hilight System [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Income Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated fair value				4,900,000
MIGC System [Member]
Property, Plant and Equipment [Line Items]
Impairments				34,600,000
MIGC System [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Income Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated fair value				15,200,000
Equipment [Member]
Property, Plant and Equipment [Line Items]
Impairments				23,300,000
GNB NGL Pipeline [Member]
Property, Plant and Equipment [Line Items]
Impairments				10,900,000
GNB NGL Pipeline [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Income Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated fair value				10,000,000
Chipeta Complex [Member]
Property, Plant and Equipment [Line Items]
Impairments				5,600,000
Chipeta Complex [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Valuation, Market Approach [Member]
Property, Plant and Equipment [Line Items]
Estimated salvage value				$ 1,500,000
[1]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.

Equity Investments - Equity Inv

Equity Investments - Equity Investments Table (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019		Mar. 31, 2018	[1]
Schedule of Equity Method Investments [Line Items]
Balance	[1]	$ 1,092,088
Acquisitions		92,546
Equity income, net	[2]	57,992		$ 30,229
Contributions		36,543	[3]	0
Distributions		(54,221)		(31,576)
Distributions in excess of cumulative earnings		(7,792)	[4]	$ (8,850)
Balance		1,217,156
Fort Union [Member]
Schedule of Equity Method Investments [Line Items]
Balance		2,259
Acquisitions		0
Equity income, net		(573)
Contributions	[3]	0
Distributions		0
Distributions in excess of cumulative earnings	[4]	(237)
Balance		1,449
White Cliffs [Member]
Schedule of Equity Method Investments [Line Items]
Balance		43,020
Acquisitions		0
Equity income, net		3,225
Contributions	[3]	1,845
Distributions		(3,079)
Distributions in excess of cumulative earnings	[4]	(935)
Balance		44,076
Rendezvous [Member]
Schedule of Equity Method Investments [Line Items]
Balance		37,841
Acquisitions		0
Equity income, net		121
Contributions	[3]	0
Distributions		(607)
Distributions in excess of cumulative earnings	[4]	(671)
Balance		36,684
Mont Belvieu JV [Member]
Schedule of Equity Method Investments [Line Items]
Balance		104,949
Acquisitions		0
Equity income, net		7,127
Contributions	[3]	0
Distributions		(4,500)
Distributions in excess of cumulative earnings	[4]	0
Balance		107,576
Texas Express Gathering [Member]
Schedule of Equity Method Investments [Line Items]
Balance		19,358
Acquisitions		0
Equity income, net		830
Contributions	[3]	0
Distributions		(835)
Distributions in excess of cumulative earnings	[4]	(316)
Balance		19,037
Texas Express Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Balance		193,198
Acquisitions		0
Equity income, net		8,665
Contributions	[3]	6,000
Distributions		(9,865)
Distributions in excess of cumulative earnings	[4]	0
Balance		197,998
Front Range Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Balance		176,436
Acquisitions		0
Equity income, net		7,125
Contributions	[3]	0
Distributions		(6,480)
Distributions in excess of cumulative earnings	[4]	0
Balance		177,081
Whitethorn LLC [Member]
Schedule of Equity Method Investments [Line Items]
Balance		161,858
Acquisitions		0
Equity income, net		21,860
Contributions	[3]	3,228
Distributions		(17,058)
Distributions in excess of cumulative earnings	[4]	(5,213)
Balance		164,675
Cactus II [Member]
Schedule of Equity Method Investments [Line Items]
Balance		106,360
Acquisitions		0
Equity income, net		0
Contributions	[3]	17,791
Distributions		0
Distributions in excess of cumulative earnings	[4]	0
Balance		124,151
Capitalized interest		1,500
Saddlehorn [Member]
Schedule of Equity Method Investments [Line Items]
Balance		108,507
Acquisitions		0
Equity income, net		4,830
Contributions	[3]	0
Distributions		(5,189)
Distributions in excess of cumulative earnings	[4]	0
Balance		108,148
Panola [Member]
Schedule of Equity Method Investments [Line Items]
Balance		22,769
Acquisitions		0
Equity income, net		582
Contributions	[3]	0
Distributions		(582)
Distributions in excess of cumulative earnings	[4]	(228)
Balance		22,541
Mi Vida [Member]
Schedule of Equity Method Investments [Line Items]
Balance		64,632
Acquisitions		0
Equity income, net		1,685
Contributions	[3]	0
Distributions		(2,451)
Distributions in excess of cumulative earnings	[4]	0
Balance		63,866
Ranch Westex [Member]
Schedule of Equity Method Investments [Line Items]
Balance		50,901
Acquisitions		0
Equity income, net		2,027
Contributions	[3]	0
Distributions		(3,087)
Distributions in excess of cumulative earnings	[4]	(132)
Balance		49,709
Red Bluff Express [Member]
Schedule of Equity Method Investments [Line Items]
Balance		0
Acquisitions		92,546
Equity income, net		488
Contributions	[3]	7,679
Distributions		(488)
Distributions in excess of cumulative earnings	[4]	(60)
Balance		$ 100,165
[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.

Components of Working Capital -

Components of Working Capital - Accounts Receivable, Net Table (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Trade receivables, net		$ 212,342	$ 221,119
Other receivables, net		81	45
Total accounts receivable, net	[1]	212,423	221,164	[2]
WES Operating [Member]
Trade receivables, net		214,067	221,328
Other receivables, net		81	45
Total accounts receivable, net	[3]	$ 214,148	$ 221,373	[2]
[1]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $68.5 million and $72.6 million as of March 31, 2019, and December 31, 2018, respectively.
[2]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[3]	Accounts receivable, net includes amounts receivable from affiliates (as defined in Note 1) of $70.2 million and $72.8 million as of March 31, 2019, and December 31, 2018, respectively.

Components of Working Capital_2

Components of Working Capital - Other Current Assets Table (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
NGLs inventory		$ 6,861	$ 6,466
Imbalance receivables		5,800	9,035
Prepaid insurance		1,064	1,972
Contract assets		7,172	5,399
Other		2,575	4,184
Total other current assets	[1]	23,472	27,056	[2]
WES Operating [Member]
NGLs inventory		6,861	6,466
Imbalance receivables		5,800	9,035
Prepaid insurance		1,026	1,972
Contract assets		7,172	5,399
Other		2,575	3,309
Total other current assets	[3]	$ 23,434	$ 26,181	[2]
[1]	Other current assets includes affiliate amounts of $7.4 million and $3.7 million as of March 31, 2019, and December 31, 2018, respectively.
[2]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[3]	Other current assets includes affiliate amounts of $7.4 million and $3.7 million as of March 31, 2019, and December 31, 2018, respectively.

Components of Working Capital_3

Components of Working Capital - Accrued Liabilities Table (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Accrued interest expense		$ 55,831	$ 70,968
Short-term asset retirement obligations		23,033	25,938
Short-term remediation and reclamation obligations		863	863
Income taxes payable		861	384
Contract liabilities		6,364	16,235
Other	[1]	54,490	14,760
Total accrued liabilities	[2]	141,442	129,148	[3]
WES Operating [Member]
Accrued interest expense		55,831	70,959
Short-term asset retirement obligations		23,033	25,938
Short-term remediation and reclamation obligations		863	863
Income taxes payable		861	384
Contract liabilities		6,364	16,235
Other	[1]	54,315	13,495
Total accrued liabilities	[4]	$ 141,267	$ 127,874	[3]
[1]	Includes amounts related to WES Operating’s interest-rate swaps as of March 31, 2019 and December 31, 2018 (see Note 10). Includes lease liabilities related to the implementation of ASU 2016-02, Leases (Topic 842) as of March 31, 2019 (see Note 1).
[2]	Accrued liabilities includes affiliate amounts of $3.5 million and $2.2 million as of March 31, 2019, and December 31, 2018, respectively.
[3]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[4]	Accrued liabilities includes affiliate amounts of $3.5 million and $2.2 million as of March 31, 2019, and December 31, 2018, respectively.

Debt and Interest Expense - Deb

Debt and Interest Expense - Debt Outstanding Table (Details) - USD ($)		3 Months Ended
		Mar. 31, 2019	Dec. 31, 2018		Mar. 31, 2018
Debt Instrument [Line Items]
Short-term debt, principal		$ 2,000,000,000	$ 28,000,000
Short-term debt, carrying value		2,000,000,000	28,000,000	[1]
Long-term debt, carrying value		5,208,411,000	4,787,381,000	[1]
Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Short-term debt, fair value	[2]	2,000,000,000	28,000,000
Long Term Debt Obligations [Member]
Debt Instrument [Line Items]
Total long-term debt, principal		5,260,000,000	5,267,493,000
Long-term debt, carrying value		5,208,411,000	5,214,874,000
Long Term Debt Obligations [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	[2]	5,227,532,000	4,976,815,000
WES [Member] | WGP RCF [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal		0	28,000,000
Short-term debt, carrying value		0	28,000,000
WES [Member] | WGP RCF [Member] | Revolving Credit Facility [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Short-term debt, fair value	[2]	0	28,000,000
WES Operating [Member]
Debt Instrument [Line Items]
Short-term debt, carrying value		2,000,000,000	0	[1]
Long-term debt, carrying value		5,208,411,000	4,787,381,000	[1]
WES Operating [Member] | WES 364-Day Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal		2,000,000,000	0
Short-term debt, carrying value		2,000,000,000	0
WES Operating [Member] | WES 364-Day Facility [Member] | Revolving Credit Facility [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Short-term debt, fair value	[2]	2,000,000,000	0
WES Operating [Member] | RCF [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal		640,000,000	220,000,000
Long-term debt, carrying value		640,000,000	220,000,000
WES Operating [Member] | RCF [Member] | Revolving Credit Facility [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	[2]	640,000,000	220,000,000
WES Operating [Member] | APCWH Note Payable [Member]
Debt Instrument [Line Items]
Senior note, interest rate					2.54%
Principal		0	427,493,000
Long-term debt, carrying value		0	427,493,000
WES Operating [Member] | APCWH Note Payable [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	[2]	$ 0	427,493,000
WES Operating [Member] | Senior Notes [Member] | 5.375% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Senior note, interest rate		5.375%
Debt instrument, maturity date		Jun. 1, 2021
Principal		$ 500,000,000	500,000,000
Long-term debt, carrying value		497,257,000	496,959,000
WES Operating [Member] | Senior Notes [Member] | 5.375% Senior Notes due 2021 [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	[2]	$ 518,755,000	515,990,000
WES Operating [Member] | Senior Notes [Member] | 4.000% Senior Notes due 2022 [Member]
Debt Instrument [Line Items]
Senior note, interest rate		4.00%
Debt instrument, maturity date		Jul. 1, 2022
Principal		$ 670,000,000	670,000,000
Long-term debt, carrying value		669,138,000	669,078,000
WES Operating [Member] | Senior Notes [Member] | 4.000% Senior Notes due 2022 [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	[2]	$ 680,293,000	662,109,000
WES Operating [Member] | Senior Notes [Member] | 3.950% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Senior note, interest rate		3.95%
Debt instrument, maturity date		Jun. 1, 2025
Principal		$ 500,000,000	500,000,000
Long-term debt, carrying value		493,082,000	492,837,000
WES Operating [Member] | Senior Notes [Member] | 3.950% Senior Notes due 2025 [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	[2]	$ 493,788,000	466,135,000
WES Operating [Member] | Senior Notes [Member] | 4.650% Senior Notes due 2026 [Member]
Debt Instrument [Line Items]
Senior note, interest rate		4.65%
Debt instrument, maturity date		Jul. 1, 2026
Principal		$ 500,000,000	500,000,000
Long-term debt, carrying value		495,830,000	495,710,000
WES Operating [Member] | Senior Notes [Member] | 4.650% Senior Notes due 2026 [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	[2]	$ 507,034,000	483,994,000
WES Operating [Member] | Senior Notes [Member] | 4.500% Senior Notes due 2028 [Member]
Debt Instrument [Line Items]
Senior note, interest rate		4.50%
Debt instrument, maturity date		Mar. 1, 2028
Principal		$ 400,000,000	400,000,000
Long-term debt, carrying value		394,749,000	394,631,000
WES Operating [Member] | Senior Notes [Member] | 4.500% Senior Notes due 2028 [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	[2]	$ 400,050,000	377,475,000
WES Operating [Member] | Senior Notes [Member] | 4.750% Senior Notes due 2028 [Member]
Debt Instrument [Line Items]
Senior note, interest rate		4.75%
Debt instrument, maturity date		Aug. 15, 2028
Principal		$ 400,000,000	400,000,000
Long-term debt, carrying value		395,928,000	395,841,000
WES Operating [Member] | Senior Notes [Member] | 4.750% Senior Notes due 2028 [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	[2]	$ 407,849,000	384,370,000
WES Operating [Member] | Senior Notes [Member] | 5.450% Senior Notes due 2044 [Member]
Debt Instrument [Line Items]
Senior note, interest rate		5.45%
Debt instrument, maturity date		Apr. 1, 2044
Principal		$ 600,000,000	600,000,000
Long-term debt, carrying value		593,378,000	593,349,000
WES Operating [Member] | Senior Notes [Member] | 5.450% Senior Notes due 2044 [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	[2]	$ 573,949,000	522,386,000
WES Operating [Member] | Senior Notes [Member] | 5.300% Senior Notes due 2048 [Member]
Debt Instrument [Line Items]
Senior note, interest rate		5.30%
Debt instrument, maturity date		Mar. 1, 2048
Principal		$ 700,000,000	700,000,000
Long-term debt, carrying value		686,696,000	686,648,000
WES Operating [Member] | Senior Notes [Member] | 5.300% Senior Notes due 2048 [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	[2]	$ 664,278,000	605,327,000
WES Operating [Member] | Senior Notes [Member] | 5.500% Senior Notes due 2048 [Member]
Debt Instrument [Line Items]
Senior note, interest rate		5.50%
Debt instrument, maturity date		Aug. 15, 2048
Principal		$ 350,000,000	350,000,000
Long-term debt, carrying value		342,353,000	342,328,000
WES Operating [Member] | Senior Notes [Member] | 5.500% Senior Notes due 2048 [Member] | Valuation, Market Approach [Member] | Level 2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	[2]	$ 341,536,000	$ 311,536,000
[1]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[2]	Fair value is measured using the market approach and Level 2 inputs.

Debt and Interest Expense - D_2

Debt and Interest Expense - Debt Activity Table (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Changes in Debt Outstanding [Roll Forward]
Beginning balance	$ 5,242,874
Other	2,132
Ending balance	7,208,411
WES Operating [Member] | RCF [Member] | Revolving Credit Facility [Member]
Changes in Debt Outstanding [Roll Forward]
Facility borrowings	420,000
WES Operating [Member] | WES 364-Day Facility [Member] | Revolving Credit Facility [Member]
Changes in Debt Outstanding [Roll Forward]
Facility borrowings	2,000,000
WES Operating [Member] | APCWH Note Payable [Member]
Changes in Debt Outstanding [Roll Forward]
APCWH Note Payable borrowings	11,000
Repayment of APCWH Note Payable	(439,595)
WES [Member] | WGP RCF [Member] | Revolving Credit Facility [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments of facility borrowings	$ (28,000)

Debt and Interest Expense - Int

Debt and Interest Expense - Interest-Rate Swap Table (Details) - WES Operating [Member] - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Interest-rate swap, notional amount	$ 375	$ 750
Interest-Rate Swap 1 [Member]
Derivative [Line Items]
Interest-rate swap, notional amount	$ 375
Interest-rate swap, reference period start date	Dec. 31, 2019
Interest-rate swap, reference period end date	Dec. 31, 2024
Interest-rate swap, maturity date	Dec. 31, 2019
Interest-rate swap, fixed interest rate	2.662%
Interest-Rate Swap 2 [Member]
Derivative [Line Items]
Interest-rate swap, notional amount	$ 375
Interest-rate swap, reference period start date	Dec. 31, 2019
Interest-rate swap, reference period end date	Dec. 31, 2029
Interest-rate swap, maturity date	Dec. 31, 2019
Interest-rate swap, fixed interest rate	2.802%
Interest-Rate Swap 3 [Member]
Derivative [Line Items]
Interest-rate swap, notional amount	$ 375
Interest-rate swap, reference period start date	Dec. 31, 2019
Interest-rate swap, reference period end date	Dec. 31, 2049
Interest-rate swap, maturity date	Dec. 31, 2019
Interest-rate swap, fixed interest rate	2.885%

Debt and Interest Expense - I_2

Debt and Interest Expense - Interest Expense Table (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Debt Instrument [Line Items]
Interest expense	[1]	$ (65,876)	$ (38,015)	[2]
Third Parties [Member]
Debt Instrument [Line Items]
Long-term and short-term debt		(67,096)	(41,536)
Amortization of debt issuance costs and commitment fees		(3,152)	(2,864)
Capitalized interest		6,205	6,962
Interest expense		(64,043)	(37,438)
Affiliates [Member]
Debt Instrument [Line Items]
APCWH Note Payable		(1,833)	(577)
Interest expense	[3]	$ (1,833)	$ (577)
[1]	Includes affiliate (as defined in Note 1) amounts of $1.8 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively. See Note 1 and Note 10.
[2]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[3]	Includes amounts related to the APCWH Note Payable (see Note 1 and Note 10).

Debt and Interest Expense - Add

Debt and Interest Expense - Additional Information (Details) - USD ($)		Feb. 15, 2019	Mar. 31, 2019	Mar. 31, 2018		Feb. 28, 2019	Dec. 31, 2018		Dec. 19, 2018	Feb. 16, 2018	Jun. 30, 2017
Debt Instrument [Line Items]
APCWH Note Payable, maximum borrowing	[1]		$ 0				$ 427,493,000	[2]
Gain (loss) on interest-rate swaps			(35,638,000)	$ 0	[2]
WES [Member] | Revolving Credit Facility [Member] | WGP RCF [Member]
Debt Instrument [Line Items]
Facility, maximum borrowing capacity										$ 35,000,000
Repayments of facility borrowings			28,000,000
WES Operating [Member]
Debt Instrument [Line Items]
APCWH Note Payable, maximum borrowing	[3]		0				427,493,000	[2]
Gain (loss) on interest-rate swaps			(35,638,000)	$ 0	[2]
WES Operating [Member] | Not Designated as Hedging Instrument [Member]
Debt Instrument [Line Items]
Interest-rate swap, notional amount			375,000,000				750,000,000
WES Operating [Member] | Interest-Rate Swap [Member]
Debt Instrument [Line Items]
Gain (loss) on interest-rate swaps			(35,638,000)
WES Operating [Member] | Interest-Rate Swap [Member] | Not Designated as Hedging Instrument [Member]
Debt Instrument [Line Items]
Interest-rate swap, collateral posted if credit risk related provision triggered			18,600,000
Interest-rate swap, aggregate fair value of swaps with credit risk related features for which a net liability position existed			35,100,000				5,700,000
WES Operating [Member] | Interest-Rate Swap [Member] | Not Designated as Hedging Instrument [Member] | Accrued Liabilities [Member]
Debt Instrument [Line Items]
Interest-rate swap, liability fair value			$ 43,600,000				$ 8,000,000
WES Operating [Member] | APCWH Note Payable [Member]
Debt Instrument [Line Items]
APCWH Note Payable, interest rate				2.54%
WES Operating [Member] | APCWH Note Payable [Member] | Maximum [Member]
Debt Instrument [Line Items]
APCWH Note Payable, maximum borrowing											$ 500,000,000
WES Operating [Member] | Revolving Credit Facility [Member] | RCF [Member]
Debt Instrument [Line Items]
Facility, maximum borrowing capacity						$ 2,000,000,000				$ 1,500,000,000
Facility, expiration date		Feb. 15, 2024
Facility, accordion feature amount						500,000,000
Facility, expandable maximum borrowing capacity						$ 2,500,000,000
Facility, fee rate			0.20%	0.20%
Facility, outstanding borrowings			$ 640,000,000
Facility, available borrowing capacity			$ 1,400,000,000
Facility, interest rate at period end			3.79%	3.18%
Facility, outstanding letters of credit			$ 4,600,000
WES Operating [Member] | Revolving Credit Facility [Member] | RCF [Member] | Minimum [Member]
Debt Instrument [Line Items]
Facility, fee rate			0.125%
WES Operating [Member] | Revolving Credit Facility [Member] | RCF [Member] | Maximum [Member]
Debt Instrument [Line Items]
Facility, fee rate			0.25%
WES Operating [Member] | Revolving Credit Facility [Member] | RCF [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Debt Instrument [Line Items]
Facility, applicable margin added			1.00%
WES Operating [Member] | Revolving Credit Facility [Member] | RCF [Member] | London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Debt Instrument [Line Items]
Facility, applicable margin added			1.50%
WES Operating [Member] | Revolving Credit Facility [Member] | RCF [Member] | London Interbank Offered Rate (LIBOR) [Member] | Alternate Base Rate [Member]
Debt Instrument [Line Items]
Facility, applicable margin added			1.00%
WES Operating [Member] | Revolving Credit Facility [Member] | RCF [Member] | Percentage Above Federal Funds Effective Rate [Member] | Alternate Base Rate [Member]
Debt Instrument [Line Items]
Facility, applicable margin added			0.50%
WES Operating [Member] | Revolving Credit Facility [Member] | RCF [Member] | Base Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Facility, applicable margin added			0.00%
WES Operating [Member] | Revolving Credit Facility [Member] | RCF [Member] | Base Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Facility, applicable margin added			0.50%
WES Operating [Member] | Revolving Credit Facility [Member] | WES 364-Day Facility [Member]
Debt Instrument [Line Items]
Facility, maximum borrowing capacity									$ 2,000,000,000
Facility, outstanding borrowings			$ 2,000,000,000
Facility, interest rate at period end			3.87%
WES Operating [Member] | Revolving Credit Facility [Member] | WES 364-Day Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Debt Instrument [Line Items]
Facility, applicable margin added			1.00%
WES Operating [Member] | Revolving Credit Facility [Member] | WES 364-Day Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Debt Instrument [Line Items]
Facility, applicable margin added			1.625%
WES Operating [Member] | Revolving Credit Facility [Member] | WES 364-Day Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Alternate Base Rate [Member]
Debt Instrument [Line Items]
Facility, applicable margin added			1.00%
WES Operating [Member] | Revolving Credit Facility [Member] | WES 364-Day Facility [Member] | Percentage Above Federal Funds Effective Rate [Member] | Alternate Base Rate [Member]
Debt Instrument [Line Items]
Facility, applicable margin added			0.50%
WES Operating [Member] | Revolving Credit Facility [Member] | WES 364-Day Facility [Member] | Base Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Facility, applicable margin added			0.00%
WES Operating [Member] | Revolving Credit Facility [Member] | WES 364-Day Facility [Member] | Base Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Facility, applicable margin added			0.625%
[1]	See Note 1 and Note 6.
[2]	Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.
[3]	See Note 1 and Note 6.

Leases - Summary of Leases Tabl

Leases - Summary of Leases Table (Details) $ in Thousands	Mar. 31, 2019USD ($)
Leases [Abstract]
Operating leases - Other assets	$ 10,002
Operating leases - Accrued liabilities	7,560
Operating leases - Other liabilities	$ 3,343
Weighted-average remaining lease term (years)	4 years
Weighted-average discount rate	4.10%

Leases - Operating Leases Liabi

Leases - Operating Leases Liability Maturity Table (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Remainder of 2019	$ 5,588
2019		$ 8,711
2020	2,215	2,236
2021	612	460
2022	618	467
2023	625	473
Thereafter	1,658	1,547
Total lease payments	11,316	$ 13,894
Less portion representing imputed interest	413
Total lease liabilities	$ 10,903

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Leases [Abstract]
Sublease income	$ 0.1
Total lease cost	1.8	$ 13.8
Operating cash payments for amounts included in the measurement of lease liabilities	$ 2