Equity Plan - Unrecognized Compensation Cost - Nonvested Stock Options (Details) - Options $ in Thousands	6 Months Ended
Jun. 30, 2018 USD ($)
Unrecognized Compensation Cost
Total unrecognized compensation cost related to nonvested stock options granted	$ 1,744
Expected weighted-average period for recognition of compensation costs related to nonvested stock options	2 years 11 months 23 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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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration