Janssen Collaboration Agreement - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Contract liabilities:
Balance at beginning of period			$ 31,752
Balance at end of period	$ 7,970		7,970
Payable to collaboration partner - related party
Balance at End of Period	764		764
License and collaboration revenue - related party	6,117	$ 8,781	28,572	$ 8,781
Revenue recognized from contract liability balance at beginning of period	5,900	0	27,900	0
Revenue recognized from performance obligations in previous periods	0	0	0	0
Janssen Biotech, Inc. | License and Collaboration Agreement
Contract assets:
Balance at beginning of period	5,785		1,816
Additions	1,385	520	6,012	520
Deductions	(2,584)		(3,242)
Balance at end of period	4,586	520	4,586	520
Contract liabilities:
Balance at beginning of period	13,202		31,752
Additions	696	50,132	4,147	50,132
Deductions	(5,928)	(8,393)	(27,929)	(8,393)
Balance at end of period	7,970	$ 41,739	7,970	$ 41,739
Payable to collaboration partner - related party
Balance at Beginning of Period	276
Additions	488		1,068
Deductions			(304)
Balance at End of Period	$ 764		$ 764