Commitments and Contingencies - Research Collaboration and Licensing Agreements Narrative (Details) - Agreements with Royalty Provisions - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Research Collaboration and Licensing Arrangements [Line Items]
Royalty rate minimum	0.50%
Royalty rate maximum	11.50%
Royalty expense	$ 36.7	$ 30.8	$ 125.3