Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule of stock-based compensation expense
Stock-based compensation	$ 1,833	$ 1,230	$ 5,212	$ 3,861
Stock options [Member]
Schedule of stock-based compensation expense
Stock-based compensation	393	249	1,107	820
RSAs and RSUs [Member]
Schedule of stock-based compensation expense
Stock-based compensation	456	445	1,399	1,580
Performance Stock Units (PSUs) [Member]
Schedule of stock-based compensation expense
Stock-based compensation	385	536	1,373	1,461
Performance Based Options (PBOs) [Member]
Schedule of stock-based compensation expense
Stock-based compensation	599	0	1,333	0
Research and development [Member]
Schedule of stock-based compensation expense
Stock-based compensation	386	246	1,050	688
Selling, General and Administrative Expenses [Member]
Schedule of stock-based compensation expense
Stock-based compensation	$ 1,447	$ 984	$ 4,162	$ 3,173