Intangible Assets - Carrying Value of Intangibles Assets (Detail) $ in Thousands	Dec. 31, 2014 USD ($)
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets	$ 1,870
CERE-110 for the treatment of Alzheimer's disease ("IPR&D") [Member]
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets	1,640
CERE-120 for the treatment of Parkinson's disease ("IPR&D") [Member]
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets	$ 230