Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Exercise price per share or per unit of warrants or rights outstanding.

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Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

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Gross amount of debt extinguished.

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The cash inflow from the additional capital contribution to the entity.

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Number of options outstanding, including both vested and non-vested options.

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Number of new stock issued during the period.

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Stockholder's Equity and Stock-Based Compensation Expense - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended
	Mar. 21, 2019	Feb. 21, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of warrants issued to purchase additional shares of common stock (in warrants)		1,820,000
Net proceeds from issuance of stock			$ 47,219	$ 0
Amount of debt retired			$ 28,500
Warrant exercise price (usd per warrant)		$ 33.60
Number of shares issued or reserved for future issuance under outstanding stock options			871,757	838,582
Stock-based compensation expense			$ 812	$ 634
Forecast
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential additional proceeds from exercise of warrants	$ 61,200
Restricted Stock and Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of restricted stock and shares reserved for restricted stock units outstanding			182,053	203,622	201,702
Stock Appreciation Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued or reserved for future issuance under outstanding stock options			530,865	1,416,133	565,864
Stock-based compensation expense			$ 800	$ 200
Common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
New issues of equity in public offering (in shares)		1,820,000
Public offering price of stock (usd per share)		$ 27.50