Product Revenue - Product Sales (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Product revenue, net
Product revenue - net	$ 58,670	$ 54,202	$ 52,804	$ 32,544	$ 18,174	$ 220,213	$ 0	$ 0	$ 198,220	$ 238,387	$ 1,070
Product revenue, net
Product revenue, net
Product revenue - gross									138,046	28,428	0
Less: Rebates and sales returns									(7,161)	(4,000)	0
Product revenue - net									$ 130,885	$ 24,428	$ 0