Summary Results of Regulus Operation (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statements of Comprehensive Loss Data:
Net revenues	$ 9,462	$ 13,789	$ 8,601
Operating expenses	17,733	20,926	24,099
Loss from operations	(8,271)	(7,137)	(15,498)
Other (expense) income	(2,289)	(259)	(91)
Income tax benefit (expense)	28	(206)	30
Net loss	$ (10,532)	$ (7,602)	$ (15,559)