Revenues - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) agreement
Summary Of Deferred Revenue [Line Items]
Contract revenue recognized	$ 7,498
Nippon Shinyaku
Summary Of Deferred Revenue [Line Items]
Number of license, development, and commercialization agreements | agreement	2
Contract revenue recognized	$ 7,500
Revenue, performance obligation, description of timing	The deferred revenue balances are being recognized over an average of four years representing the period we expect to perform our research and developments obligations under each agreement.
Minimum
Summary Of Deferred Revenue [Line Items]
Payment terms, range	30 days
Maximum
Summary Of Deferred Revenue [Line Items]
Payment terms, range	45 days