Related-Party Transactions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related-Party Transactions
Revenues	$ 10us-gaap_RevenueFromRelatedParties	$ 9us-gaap_RevenueFromRelatedParties	$ 5us-gaap_RevenueFromRelatedParties
Expenses	1,068	965	874
Accounts receivable	26us-gaap_DueFromRelatedPartiesCurrent	18us-gaap_DueFromRelatedPartiesCurrent
Accounts payable	123	100
Short-term liability	149us-gaap_DueToRelatedPartiesCurrent
Long-term liability	$ 1us-gaap_DueToRelatedPartiesNoncurrent	$ 69us-gaap_DueToRelatedPartiesNoncurrent

Amount for accounts payable to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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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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- Definition

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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- Definition

Portion of the carrying amount as of the balance sheet date of obligations due all related parties that is payable after one year or beyond the normal operating cycle if longer.

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- Definition

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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