Royalty Agreements - Narrative (Details) - BioSphere APHP Royalty - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Royalty Agreements [Line Items]
Current royalty rate	5.00%
Future royalty rate	2.50%
Royalty expense	$ 1.8	$ 1.5	$ 1.5