Investments - Cost and Equity Method Investments (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Long-term Investment
Schedule of Equity Method Investments [Line Items]
Cost and equity method investments included in long-term investments	$ 124	$ 184

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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