Stock-Based Compensation - Options Granted after April 23, 2013 - Unrecognized Compensation Expense (Details) - Options granted after April 23, 2013 - Stock options $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($)
Stock-Based Compensation
Unrecognized compensation expense related to unvested stock options	$ 1,429
Weighted-average period for recognizing unrecognized compensation expense related to unvested stock options (in years)	2 years 3 months 22 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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