Investments - Cost and Equity Method Investments (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Long-term Investments
Schedule of Equity Method Investments [Line Items]
Cost and equity method investments	$ 119	$ 118

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.

No definition available.

Name:	us-gaap_ScheduleOfEquityMethodInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration