Stockholder's Equity and Stock-Based Compensation Expense - Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares issued or committed for issuance under outstanding stock options (in shares)	647,483	766,659
Stock-based compensation expense	$ 1,094	$ 2,831
Restricted Stock and Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares of restricted stock and shares reserved for restricted stock units outstanding (in shares)	873,371	794,994	908,754
Stock Appreciation Rights
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares issued or committed for issuance under outstanding stock options (in shares)	906,850	1,063,013	954,679
Stock-based compensation expense	$ (1,000)	$ 2,000

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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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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