Restructuring - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended
	Nov. 30, 2012 Position	Mar. 31, 2014	Mar. 31, 2013
Restructuring Cost and Reserve [Line Items]
Reduction in workforce, number of employees	21
Restructuring charge		$ 9	$ 462
Research and Development Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charge		100	300
General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charge			$ 200