Restructuring - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended	6 Months Ended
	Nov. 30, 2012 Position	Jun. 30, 2013
Restructuring Cost and Reserve [Line Items]
Reduction in workforce, number of employees	21
Restructuring charges included severance and related costs		$ 671
Research and development
Restructuring Cost and Reserve [Line Items]
Restructuring charges included severance and related costs		300
General and administrative
Restructuring Cost and Reserve [Line Items]
Restructuring charges included severance and related costs		$ 300