Summary of Significant Accounting Policies - Acc Liab (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Accrued Liabilities
Accrued contract payments	$ 4,901	$ 1,980
Accrued clinical trial costs	8,400	4,700
Accrued professional services	723	865
Accrued employee benefits	574	676
Accrued public reporting charges	156	156
Accrued interest on convertible senior notes		2,388
Other current accrued liabilities	1,013	385
Total	15,767	11,150
Deferred revenue	$ 6,800	$ 7,100