Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Related Party Transaction
Transportation and storage of natural gas	$ 5us-gaap_RevenueFromRelatedParties	$ 20us-gaap_RevenueFromRelatedParties
Operating, maintenance and general	12	12
Interest income - affiliates	0us-gaap_InterestIncomeRelatedParty	5us-gaap_InterestIncomeRelatedParty
Equity in earnings (losses) from unconsolidated investments	$ 4	$ (8)

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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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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