Revenue Recognition and Adoption of New Accounting Pronouncement - Summary of Revenues Disaggregated by Recognition at Point in Time and Over Time (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Contract revenues
Total revenues	$ 19,391	$ 669	$ 20,457	$ 2,139
Point in Time [Member] \| Healios License Agreement [Member]
Contract revenues
Total revenues	18,003		18,230
Point in Time [Member] \| Healios License Agreement [Member] \| License fee [Member]
Contract revenues
Total revenues	17,530		17,530
Point in Time [Member] \| Healios License Agreement [Member] \| Product supply [Member]
Contract revenues
Total revenues	223		450
Point in Time [Member] \| Healios License Agreement [Member] \| Other Contract [Member]
Contract revenues
Total revenues	250		250
Over Time [Member] \| Healios License Agreement [Member]
Contract revenues
Total revenues	1,002		1,123
Over Time [Member] \| Healios License Agreement [Member] \| Service [Member]
Contract revenues
Total revenues	$ 1,002		$ 1,123