Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule of stock-based compensation expense
Stock-based compensation	$ 1,711	$ 1,242	$ 3,379	$ 2,631
Stock options [Member]
Schedule of stock-based compensation expense
Stock-based compensation	380	267	714	571
RSAs and RSUs [Member]
Schedule of stock-based compensation expense
Stock-based compensation	484	561	943	1,135
Performance stock units [Member]
Schedule of stock-based compensation expense
Stock-based compensation	348	414	988	925
Performance Based Options (PBOs) [Member]
Schedule of stock-based compensation expense
Stock-based compensation	499	0	734	0
Research and development [Member]
Schedule of stock-based compensation expense
Stock-based compensation	342	222	664	442
Selling, General and Administrative Expenses [Member]
Schedule of stock-based compensation expense
Stock-based compensation	$ 1,369	$ 1,020	$ 2,715	$ 2,189