Product Revenue Reserves and Allowances Product Revenue Reserves and Allowances - Narrative (Details) - Product Revenue Allowance and Reserves - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2018	Sep. 30, 2017
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Provision related to sales in the current year	$ 10,600	$ 8,600	$ 6,100	$ 25,329	$ 1,443
Adjustments related to prior period sales	(77)	29	(245)	293	0
Credits and payments made	$ (8,838)	$ (6,745)	$ (2,981)	$ 18,464	$ 0