Intangible Assets - Summary of Assets, Estimated Fair Values (Detail) (Ceregene, Inc. [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets	$ 1,870	$ 1,870
CERE-110 for the treatment of Alzheimer's disease [Member]
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets	1,640	1,640
CERE-120 for the treatment of Parkinson's disease [Member]
Finite-Lived Intangible Assets [Line Items]
Total identifiable intangible assets	$ 230	$ 230