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
Stock-based compensation expense
Total stock-based compensation expense	$ 25,016	$ 12,919	$ 66,925	$ 34,064
Research and development
Stock-based compensation expense
Total stock-based compensation expense	8,545	5,605	23,532	13,826
Selling, general and administrative
Stock-based compensation expense
Total stock-based compensation expense	$ 16,471	$ 7,314	$ 43,393	$ 20,238