Income Taxes (Details) - USD ($) $ in Billions	Sep. 30, 2017	Dec. 31, 2016
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Gross unrecognized tax benefits	$ 5.1	$ 5.4
Unrecognized tax benefits that would impact effective tax rate	$ 3.9	$ 4.3

The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant