Legal Proceedings Legal Proceedings (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Estimated accruals for legal proceedings and inquiries	$ 0.9	$ 4.3

Amount of loss contingency liability.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

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