Stock-based Compensation - Performance Unit Awards - Additional Disclosures (Details) - Performance Unit Awards $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Stock-based Compensation
Unrecognized expenses	$ 0.1
Weighted-average remaining recognition period (in years)	1 year 2 months 12 days

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration