Stock Option Plans, Allocation of Recognized Period Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
All stock-based compensation expense [Abstract]
Total stock-based compensation expense	$ 7,951	$ 11,050	$ 4,455
Research and Development [Member]
All stock-based compensation expense [Abstract]
Total stock-based compensation expense	2,608	3,267	1,310
General and Administrative [Member]
All stock-based compensation expense [Abstract]
Total stock-based compensation expense	$ 5,343	$ 7,783	$ 3,145