Collaboration Revenue - Changes in Contract Asset and Contract Liabilities (Detail) - ASU 2014-09 [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract assets, Balance at Beginning of Period	$ 510	$ 306
Contract assets, Additions	175
Contract assets, Deductions	(510)	(8)
Contract assets, Balance at End of Period	175	298
Contract liabilities:
Balance at Beginning of Period	123,783	108,814
Additions	175
Deductions	(3,766)	(3,015)
Balance at End of Period	$ 120,192	$ 105,799