Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenues:
Product revenues	$ 95,619	$ 85,487	$ 188,244	$ 169,467
Operating expenses:
General and administrative	18,487	18,395	38,205	35,146
Net income	8,317	$ (2,739)	4,542	$ (3,545)
Assets:
Accounts receivable, net	48,982		48,982			$ 31,161
Equity:
Accumulated deficit	(227,460)		(227,460)			$ (245,945)
Balance Without Adoption of ASC 606 | ASU 2014-09
Revenues:
Product revenues	95,789		189,828
Operating expenses:
General and administrative	18,990		39,732
Net income	7,984		4,599
Assets:
Accounts receivable, net	34,549		34,549
Equity:
Accumulated deficit	(241,526)		(241,526)
Adjustments | ASU 2014-09
Revenues:
Product revenues	(170)		(1,584)
Operating expenses:
General and administrative	(503)		(1,527)
Net income	333		(57)
Assets:
Accounts receivable, net	14,433		14,433		$ 14,100
Equity:
Accumulated deficit	$ 14,066		$ 14,066		$ 14,100