Cash outflow for capital contributions subsequent to the initial purchase of interest in equity method investments.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting that was acquired during the period.

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Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest, Units

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Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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The aggregate amount of receivables to be collected from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth, at the financial statement date. which are usually due within one year (or one business cycle).

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Carrying amount as of the balance sheet date of obligations due all related parties. For classified balance sheets, represents the current portion of such liabilities (due within one year or within the normal operating cycle if longer).

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Percentage investment held by members or limited partners of limited liability company (LLC) or limited partnership (LP).

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The cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

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Amount of divestiture of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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Related Party Transactions - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Net investments in equity method investees				$ 216	$ 250
Oxy
Related Party Transaction [Line Items]
Limited partner interest	4.00%
Revenues		$ 280	$ 220	558	453
Trade accounts receiveable and other receivables	$ 1,115	1,115		1,115		$ 1,075
Accounts payable	1,012	1,012		1,012		990
Equity Method Investee
Related Party Transaction [Line Items]
Revenues		3	1	5	2
Costs related to services and product purchases		135	108	265	193
Trade accounts receiveable and other receivables	46	46		46		26
Accounts payable	$ 106	106		$ 106		$ 41
Cactus II Pipeline LLC
Related Party Transaction [Line Items]
Reduction of property and equipment from deconsolidation		74
Proceeds from deconsolidation		$ 26
Cactus II Pipeline LLC \| Third Party
Related Party Transaction [Line Items]
Interest acquired	15.00%	15.00%		15.00%
Cactus II Pipeline LLC \| Oxy
Related Party Transaction [Line Items]
Interest acquired	20.00%	20.00%		20.00%
Agreement To Transport Crude Oil On Pipeline Of Equity Method Investee \| Equity Method Investee
Related Party Transaction [Line Items]
Ownership percentage	50.00%	50.00%		50.00%
Other long-term liabilities and deferred credits \| Cactus II Pipeline LLC
Related Party Transaction [Line Items]
Deferred revenue	$ 100	$ 100		$ 100
Joint Tariff \| Equity Method Investee
Related Party Transaction [Line Items]
Costs related to services and product purchases		$ 71	$ 52	$ 139	$ 93
AAP \| Oxy
Related Party Transaction [Line Items]
Limited partner interest	11.00%
PAGP \| Shares Class C
Related Party Transaction [Line Items]
Ownership interest (in units)				515,460,375		510,925,432