Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Stock-Based Compensation
Stock options and other incentive awards granted (in shares)	150,404	178,586	155,080	183,736
Allocated share-based compensation expense	$ 2,205	$ 2,345	$ 4,833	$ 5,110
Stock-Based Compensation
Unrecognized stock-based compensation cost, net of estimated forfeiture	12,000		12,000
Research and development
Stock-Based Compensation
Allocated share-based compensation expense	81	150	242	341
Selling, general and administrative expenses
Stock-Based Compensation
Allocated share-based compensation expense	$ 2,124	$ 2,195	$ 4,591	$ 4,769

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

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